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Achilles tendinopathy

92 citationsUpdated Sep 2026

Overview

Achilles tendinopathy is a degenerative process [4] that primarily affects the noninsertional watershed area, located 2 to 6 cm proximal to the calcaneal insertion [10]. The condition manifests as peritendinitis without tendinosis, peritendinitis with tendinosis, or isolated tendinosis [10]. While acute peritendinitis presents with pain and swelling [10], chronic tendinosis may be asymptomatic, characterized by bulbous nodularity that moves with passive ankle motion [10]. Chronic degenerative changes can lead to calcification [10], and MRI is useful for evaluating the extent of these changes for preoperative planning [10]. In athletes, the mechanical properties of the Achilles aponeurosis are altered [44], though repetitive mechanical loading may reduce musculotendinous unit compliance [44].

Nonoperative management is the mainstay of treatment for all Achilles tendon diagnoses [1] and yields excellent clinical results for noninsertional cases [3]. Most patients fully recover symptoms and function with exercise alone [9], and extracorporeal shockwave therapy (ESWT) improves pain and functional outcomes compared to other nonsurgical treatments [15]. However, a wait-and-see strategy is ineffective for chronic recalcitrant tendinopathy [18]. Platelet-rich plasma (PRP) injections show no benefit over placebo [31, 66] and should not be used until high-quality randomized controlled trials demonstrate clear clinical benefit [104].

Surgical intervention is indicated when conservative treatment fails after at least 6 months [10] or for refractory cases [4, 8]. Options include ventral paratenon stripping, open tendon debridement, and tendon reconstruction with transfers [10]. For extensive disease involving more than 50% of the tendon volume, reconstruction procedures remain the gold standard despite significant recovery times and potential complications [10]. Gastrocnemius recession is an alternative with less morbidity [10], while endoscopic debridement offers good results with shortened recovery [10]. Flexor hallucis longus (FHL) tendon transfer is widely supported for augmentation, with similar outcomes reported for flexor digitorum longus transfers [10]. Open surgery for midportion tendinopathy is safe and effective in the medium term [29], and multiple percutaneous longitudinal tenotomies are safe, low-cost, and effective long-term in runners [32]. No definite recommendations exist regarding the optimal surgical treatment for midportion Achilles tendinopathy [41] or insertional Achilles tendinopathy [67].

Anatomy & Pathophysiology

Anatomy

The Achilles tendon is the largest tendon in the body, formed by the confluence of the soleus muscle and the medial and lateral heads of the gastrocnemius muscle in the distal calf [20]. It inserts at the calcaneal tuberosity, separated from the underlying bone by the retrocalcaneal bursa [110]. As the only musculotendinous unit crossing two major joints (knee and ankle, as well as subtalar), it acts as the major plantar flexor of the ankle joint and a weak knee flexor due to the gastrocnemius insertion on the posterior femoral condyles [20]. The tendon fibers undergo a 90° internal rotation, positioning medial gastrocnemius fibers posteriorly at insertion, and the tendon runs just medial to the hindfoot axis of rotation, acting as an inverter of the heel [20]. Functionally, the gastrocnemius is most effective in plantarflexion with the knee extended, whereas the soleus is most effective with the knee flexed [45].

The tendon is innervated by the tibial nerve [20]. It is surrounded by a paratenon consisting of loose areolar tissue rather than a true synovial sheath, covered medially, posteriorly, and laterally [20, 110]. Anteriorly, the tendon is marginated by the Kager fat pad [110]. The plantaris tendon is variably present as a thin slip coursing from superolateral to inferomedial along the ventral surface, inserting onto either the distal Achilles tendon or the calcaneal tuberosity [110]. Lubrication is aided by two bursae: one anterior (retrocalcaneal) and one posterior (superficial) to the tendon [20]. The sural nerve runs in the midline of the gastrocnemius-soleus muscle to the musculotendinous junction, where it crosses to the lateral side of the tendon [20].

Vascularity is supplied through the paratenon on the deep surface, muscular arterial branches within the gastrosoleus complex proximally, and small interosseous vessels at the calcaneal insertion distally [45]. The major blood supply is through the mesotendon, with the richest supply via the anterior mesentery [108]. This vascular arrangement creates a zone of relative avascularity, or vascular watershed region, 2 to 6 cm proximal to the insertion on the calcaneus [20, 45]. With increasing age, the anterior mesenteric blood supply becomes reduced [108].

Pathophysiology

Achilles tendinopathy is a degenerative process related to overuse, and the term "tendinitis" is a misnomer [4, 21]. Histopathology typically lacks markers of inflammation within the tendon [21]. The etiology, pathogenesis, and natural course are largely unknown, with histopathological studies limited to the chronic phase [2]. It remains unclear whether degenerative features are preceded by an inflammatory phase [2]. In the absence of inflammation in the chronic stage, pain may result from irritation of mechanoreceptors or triggering of nociceptive receptors [2].

The risk for developing Achilles tendinopathy is multifactorial, involving an interaction of intrinsic and extrinsic factors leading to tendon overloading [16]. Lower extremity impairments causing abnormal kinetics or kinematics that produce eccentric overload can result in injury [16]. Genes associated with the collagen-production pathway may affect tendon strength and stiffness, leading to abnormal responses during loading [16]. Individuals with a family history of tendinopathy have five times the risk of developing Achilles tendinopathy [16]. The multifactorial etiology of noninsertional Achilles tendinopathy includes overuse, mechanical imbalance, poor tissue vascularity, genetic predisposition, and use of fluoroquinolone antibiotics [46]. Noninsertional Achilles tendinopathy accounts for nearly half of all cases and is thought to involve the response to microscopic tearing [46].

Tendon injury is thought to be caused by a failed healing process resulting in altered tendon structure, neovascularization, and nerve ingrowth [16]. Abnormal vascularization of the ventral mesotenal vessels 2 to 6 cm proximal to the insertion limits blood flow to diseased tissue and decreases healing capacity [46]. Repetitive microtrauma to this hypovascular area may make it impossible for the reparative process to keep pace, leading to degenerative attrition [108]. Age-dependent changes in collagen crosslinking result in increased stiffness and loss of viscoelasticity, predisposing to injury [108]. Chronic painful Achilles tendons show ingrowth of sensory and sympathetic nerves from the paratenon with release of nociceptive substances [125]. Up to 34% of asymptomatic tendons show histopathological changes [125].

Insertional Achilles tendinopathy results from a complex interplay of mechanical loads, vascular impairment, and inflammatory responses [74]. Chronic inflammation is a feature of both mid-portion Achilles tendinopathy and rupture [38]. Pro-inflammatory profiles differ slightly in ruptured tendons, likely due to acute inflammation and increased vascularisation from recent trauma [38]. The Achilles and rotator cuff tendons share common cellular and molecular inflammatory disease mechanisms [38].

Tendinitis refers to an acute, reversible inflammatory process with healing potential, whereas tendinosis refers to a chronic, irreversible process characterized by fibrous degeneration without reparative, inflammatory cells [45]. Clinically, these represent differing ends of a continual spectrum [45]. Tendinosis of the Achilles tendon is most commonly due to hypoxia, predisposed by the relative hypovascularity of the critical zone [110]. Myxoid degeneration is the second most frequent etiology, referring to the accumulation of mucoid vacuoles among tendon fibers, which may coalesce to form interstitial tears [110]. Less common causes include lipoid degeneration, describing fat accumulation usually asymptomatic, and ossific degeneration, describing ossification often associated with a history of injury [110]. Degenerative ossification occurs proximal to the insertion, in contrast with enthesopathy at the insertion [110].

Tears of the Achilles tendon tend to occur in the critical zone, 2 to 6 cm proximal to the calcaneus [110]. Tears of the myotendinous junction proximally may occur in athletes, while insertional tears at the calcaneal tuberosity are associated with Haglund deformity [110]. Findings that may coexist with Achilles tendinopathy include paratenonitis, peritendinitis, and retrocalcaneal bursitis [110]. Bilateral retrocalcaneal bursitis should raise suspicion of an underlying inflammatory process such as rheumatoid arthritis or seronegative spondyloarthropathy [110].

A theory concerning Achilles tendon rupture is the failure of inhibiting mechanisms at the musculotendinous unit due to fatigue, with resultant eccentric overload [108]. The cause is probably a combination of a relatively hypovascular area and repetitive microtrauma causing an inflammatory reparative process unable to keep up with stresses due to decreased vascularity [108]. Mechanical overload completes the rupture [108].

Biomechanical and structural factors influence symptom presentation. A lower peak ankle inversion moment, a lower peak ankle external rotation angle, and a greater running volume are significant predictors of the onset of Achilles tendinopathy [122]. Compared with healthy controls, runners currently symptomatic with Achilles tendinopathy have a longer duration of eversion but not greater excursion or velocity of eversion [142]. The Kager fat pad deforms and its pressure changes during ankle range of motion [131]. The plantaris tendon inserting directly into the calcaneus resulted in significantly greater differential motion compared with the Achilles tendon [138]. There was no association between tendon structure and symptoms in nonoperatively treated Achilles tendinopathy [5]. However, measures of tendon morphology and mechanical properties appear to be associated with patient-reported symptoms and calf muscle function [27]. As the factors in a data-driven model of midportion Achilles tendinopathy health are uncorrelated, results of assessment of tendon structure should not be expected to be associated with lower extremity function or biopsychosocial limitations [6]. Participants with insertional Achilles tendinopathy had larger tendon diameter, lower echogenicity, higher strain, and lower stiffness compared to uninvolved sides and controls [78]. The results of a study on mechanical properties of the Achilles tendon aponeurosis provide a rationale for clinical approaches where repetitive mechanical loading may impart a positive benefit through reduced compliance of the musculotendinous unit [44]. UTC of tendon structure, Achilles tendon thickness, and foot posture did not significantly contribute to the prediction of Achilles tendinopathy [139]. Additional research is required to improve the understanding of the causative factors in Achilles tendinopathy [33].

Classification

Clinical Phenotype Classification: Achilles tendon disorders are classified by nodularity, location of pain, and the presence or absence of redness and warmth [20]. Acute paratenonitis/tendinitis is characterized by the absence of nodularity, pain throughout the entire tendon that is unaffected by range of motion, and the presence of redness and warmth [20]. Paratenonitis/tendinitis with tendinosis presents with nodularity, pain throughout the entire tendon unaffected by range of motion, and redness and warmth [20]. Tendinosis is defined by the presence of nodularity, pain that moves with range of motion, and the absence of redness and warmth [20].

Anatomic Location Classification: The most clinically useful classification distinguishes between insertional Achilles tendinopathy at the calcaneal tuberosity and noninsertional Achilles tendinopathy located 2 to 6 cm proximal to the insertion [21]. Noninsertional Achilles tendinopathy is typically located 4 to 6 cm proximal to the insertion [21]. Midportion Achilles tendinopathy is located 2–7 cm from the insertion onto the calcaneus [96]. Insertional Achilles tendinopathy is situated at the insertion of the Achilles tendon [96]. Achilles paratendinopathy is classified as acute or chronic [96].

Revised Terminology: The revised terminology for Achilles tendon-related disorders is based on anatomic location, symptoms, clinical findings, and histopathology [24]. This terminology is used by the majority of orthopedic surgeons and is increasingly used in the literature [24]. Histopathology typically does not show markers of inflammation within the tendon, making the term “tendinitis” a misnomer [21]. However, chronic inflammation is a feature of mid-portion Achilles tendinopathy [38] and Achilles tendon rupture [38]. Pro-inflammatory profiles differ slightly in ruptured tendons compared to tendinopathy, likely due to acute inflammation and increased vascularisation from recent trauma [38].

Pathophysiological Basis: Achilles tendinopathy is a degenerative condition thought to be related to overuse [21]. In the absence of inflammation in the chronic stage, pain may be caused by irritation of mechanoreceptors or triggering of nociceptive receptors [2]. Neovascularisation is part of the pathophysiological process in Achilles tendinopathy [117]. Neovascularisation has been identified in the area with tendinosis in patients with painful chronic Achilles tendinosis using grey-scale ultrasonography and colour Doppler examination [48].

Tissue Composition: The Achilles tendon midportion is a dense, fibrous connective tissue experiencing mainly tensile forces [96]. The extracellular matrix of the Achilles tendon midportion consists predominately of type I collagen, which makes up 60% of the dry weight [96]. Proteoglycans make up 0.5% and glycoproteins make up 5% of the dry weight in the Achilles tendon midportion [96]. The insertion of the Achilles tendon suffers more compressive and shear stresses, resulting in a gradual transition from fibrous to fibrocartilaginous tissue [96]. Histologically, the fibrocartilaginous tissue at the Achilles tendon insertion shows increased roundness of tendon cells and intense staining with Pas/Alcian blue [96].

Clinical Presentation and Imaging: Patients with noninsertional Achilles tendinopathy typically present with fusiform thickening or nodularity of the tendon and associated tenderness to palpation [21]. A contracture of the gastrocnemius-soleus complex is often observed in patients with noninsertional Achilles tendinopathy [21]. Weight-bearing ankle radiographs may demonstrate intratendinous calcification at the affected level in Achilles tendinopathy [21]. In insertional tendinopathy, radiographs may demonstrate an insertional osteophyte and/or Haglund deformity [21]. Haglund deformity represents a prominence at the superior, posterolateral aspect of the calcaneal tuberosity [21]. MRI or ultrasonography evaluation can detect the degree of tendon degeneration [21] and are useful for presurgical planning [21].

Diagnostic Criteria: Midportion Achilles tendinopathy is diagnosed when a spindle-shaped swelling and tenderness at the Achilles tendon 2-7 cm above its calcaneal insertion are present [57]. Retrocalcaneal bursitis is indicated by maximum tenderness localized anterior to the medial and lateral distal Achilles tendon border and posterior to the corresponding posterosuperior calcaneal aspect [57]. Specific findings at the posterosuperior calcaneal tuberosity, such as erosions or cyst formations, indicate chronic retrocalcaneal bursitis [57]. Bone spurs in the Achilles tendon insertion are considered different pathologies from midportion tendinopathy and retrocalcaneal bursitis [57]. The continuum model of tendon pathology has been used to develop ultrasound imaging-based criteria to diagnose tendinopathy [88].

Other Considerations: There is a lack of consensus regarding the best treatment options for Achilles tendinosis [4]. An evidence-based algorithm for the conservative management of midportion Achilles tendinopathy is unknown [28]. The Dutch multidisciplinary guideline on Achilles tendinopathy provides six modules developed according to the standards of the Dutch Federation of Medical Specialists [13]. The Chinese Consensus on Insertional Achilles Tendinopathy was developed by 34 experts using the Delphi method [70]. In the Chinese Consensus on Insertional Achilles Tendinopathy, strong consensus was reached for 8 statements and unanimity for 2 statements [70]. Subgroup analysis of non-drug therapies for Achilles tendinopathy is conducted based on the different locations of Achilles tendinopathy [71].

Clinical Presentation

General Characteristics and Etiology

Achilles tendinopathy is a common pathology in active individuals resulting from repetitive loading during recreational activities and occupational tasks [16]. The risk for developing this condition is likely multifactorial, related to an interaction of intrinsic and extrinsic factors that lead to tendon overloading [16]. The natural history of Achilles tendinopathy is typically a long protracted course [14]. Histopathology of Achilles tendinopathy typically does not show markers of inflammation within the tendon, making the term "tendinitis" a misnomer [21]. The condition causes apparent impairments in various aspects of lower leg muscle-tendon function [22].

Classification and Terminology

The most clinically useful classification distinguishes between insertional (at the calcaneal tuberosity) and noninsertional Achilles tendinopathy (2 to 6 cm proximal to the insertion) [21]. The revised terminology for Achilles tendon-related disorders based on anatomic location, symptoms, clinical findings, and histopathology is used by the majority of orthopedic surgeons [24]. Clinical presentation varies by pathology: * Acute paratenonitis/tendinitis: There is no nodularity, pain is located at the entire tendon with no effect from range of motion, and redness and warmth are present [20]. * Paratenonitis/tendinitis with tendinosis: There is nodularity, pain is located at the entire tendon with no effect from range of motion, and redness and warmth are present [20]. * Tendinosis: There is nodularity, pain moves with range of motion, and redness and warmth are absent [20].

Noninsertional Presentation

Patients with noninsertional Achilles tendinopathy often present with pain, swelling, and impaired performance, especially with running [46]. A tender area of fusiform thickening is localized approximately 2 to 6 cm proximal to the insertion of the tendon in noninsertional cases [46]. Patients typically have fusiform thickening or nodularity of the tendon 4 to 6 cm proximal to the insertion and associated tenderness to palpation [21]. Calcification within the tendon may ensue from chronic, degenerative tendinosis as seen on radiographs [10]. MRI demonstrates thickening of the tendon with intrasubstance intermediate signal intensity consistent with disorganized tissue in noninsertional tendinopathy [46].

Insertional Presentation

Insertional tendinopathy may be characterized by one or a combination of conditions, including retrocalcaneal bursitis, pretendinous bursitis, or insertional Achilles tendinopathy with or without calcification [37]. The patient rarely gives a history of acute injury in insertional tendinopathy; rather, it is a slow, insidious process of gradual enlargement and pain at the insertion [37]. Progressive difficulty with wearing closed-back shoes and pain after a period of rest, such as when first arising in the morning, are noted in insertional tendinopathy [37]. Pain only when wearing shoes may indicate a pretendinous bursitis, while pain when first arising in the morning is more consistent with retrocalcaneal bursitis or Achilles tendinitis [37]. Examination for insertional tendinopathy often reveals a significant contracture of the gastrocnemius complex, especially with the knee in extension [37]. A true Haglund deformity refers to a large exostosis off the posterosuperior aspect of the calcaneal tuberosity located anterior to the Achilles tendon [37].

Diagnostic Challenges and Imaging

Weight-bearing ankle radiographs may demonstrate intratendinous calcification at the affected level in noninsertional cases, and an insertional osteophyte and/or Haglund deformity in insertional cases [21]. MRI is helpful in evaluating the extent of degenerative changes, especially in preoperative planning and counseling [10]. MRI or ultrasonography evaluation are useful for presurgical planning and can detect the degree of tendon degeneration [21]. Grey-scale ultrasonography in combination with colour Doppler examination has identified neovascularisation in the area with tendinosis in patients with painful chronic Achilles tendinosis [48]. Ultrasound evidence of Achilles tendinopathy and symptom duration of three months or more are inclusion criteria for chronic mid body Achilles tendinopathy in diagnostic studies [81]. US + CD directly, and clinical assessment indirectly, can detect a close by located plantaris tendon in a high proportion of patients with midportion Achilles tendinopathy [62].

There was no association between tendon structure and symptoms in nonoperatively treated Achilles tendinopathy [5]. The results of assessment of tendon structure should not be expected to be associated with lower extremity function or biopsychosocial limitations, as the factors are uncorrelated [6]. Bilateral changes in tendon structure can occur in patients diagnosed with unilateral insertional or midportion Achilles tendinopathy [51]. The asymptomatic side should not be used as a reference in clinical practice for Achilles tendinopathy [51].

Investigations

Clinical Examination and Diagnostic Criteria

The physical examination for acute Achilles tendon rupture should include two or more of the following tests: clinical Thompson test (Simmonds squeeze test), decreased ankle plantar flexion strength, presence of a palpable gap, or increased passive ankle dorsiflexion with gentle manipulation [109]. The Thompson test is highly sensitive (96%) and specific (93%) for a complete acute Achilles rupture [53]. Achilles tendon disorders are clinically classified by nodularity, location of pain, and the presence or absence of redness and warmth [20]. In acute paratenonitis/tendinitis, pain is located in the entire tendon with no effect from range of motion, and redness and warmth are present [20]. In paratenonitis/tendinitis with tendinosis, nodularity is present, pain is located in the entire tendon with no effect from range of motion, and redness and warmth are present [20]. In tendinosis, nodularity is present, pain moves with range of motion, and redness and warmth are absent [20]. Patients with noninsertional Achilles tendinopathy typically present with fusiform thickening or nodularity of the tendon 4 to 6 cm proximal to the insertion and associated tenderness to palpation [21]. A contracture of the gastrocnemius-soleus complex is often observed in patients with Achilles tendinopathy [21]. Achilles tendinopathy causes apparent impairments in various aspects of lower leg muscle-tendon function as measured with a test battery [22]. The revised terminology for Achilles tendon-related disorders based on anatomic location, symptoms, clinical findings, and histopathology is used by the majority of orthopedic surgeons and is increasingly used in the literature [24]. The ICON meetings could be an appropriate platform to initiate a new widely supported agreement on diagnostic criteria for Achilles tendinopathy [23].

Imaging: Radiography

Plain radiography: In the case of insertional tendinopathy, radiographs may demonstrate an insertional osteophyte and/or Haglund deformity, representing a prominence at the superior, posterolateral aspect of the calcaneal tuberosity [21]. Radiographs may show calcification at the Achilles tendon insertion or a posterosuperior calcaneal prominence in insertional Achilles tendinopathy [55].

Imaging: Ultrasound

Ultrasound: Ultrasonography evaluation is useful for presurgical planning and can detect the degree of tendon degeneration [21]. Ultrasonographic follow-up of patients with mid-portion painful chronic Achilles tendinosis treated with eccentric calf muscle training showed a localised decrease in tendon thickness and a normalised tendon structure in most patients [127]. Magnetic resonance imaging techniques can be used as an adjunct to clinical evaluation by monitoring morphologic effects in clinical treatment studies of Achilles tendinopathy [42]. Ultrasound combined with color Doppler can directly detect a close-by located plantaris tendon in a high proportion of patients with midportion Achilles tendinopathy [62]. Clinical assessment can indirectly detect a close-by located plantaris tendon in patients with midportion Achilles tendinopathy [62].

Imaging: MRI

MRI: MRI evaluation is useful for presurgical planning and can detect the degree of tendon degeneration [21]. MRI is valuable for evaluating the extent of diseased tendon and allows the success of nonsurgical treatment to be predicted in insertional Achilles tendinopathy [55]. MRI revealed the highest overall diagnostic accuracy for the diagnosis of both insertional and midportion Achilles tendinopathy compared to other imaging modalities [87]. There was no statistically significant difference in favor of one imaging modality over the others in the diagnosis and monitoring of Achilles tendinopathy [87]. A computerized 3-D seed-growing technique to monitor and evaluate the volume of the Achilles tendon and mean intratendinous signal using MR imaging shows an overall excellent reliability regarding inter- as well as intra-observer reliability [130]. MRI-derived measures of Achilles tendon fat content may be able to distinguish xanthomas from control and tendinopathic tissue [93]. Achilles tendon thickness of more than 6.1 mm and intratendinous abnormality of over 48.8% were confirmed to be diagnostic cutoff values for insertional Achilles tendinopathy [128]. Interposed tissue between the tendon stumps is suitable for repair of chronic Achilles tendon rupture if preoperative MRI shows a thickened fusiform-shaped Achilles tendon with diffuse intratendinous high-signal alterations throughout [129]. Intra-tendon MRI abnormalities are frequent in chronic Achilles tendon rupture but likely represent non-pathologic cicatricial remodeling [119]. MRI and ultrasonography can both be used to confirm an Achilles tendon rupture in the case of ambiguous physical examination findings but are not routinely necessary [53]. MRI and ultrasonography may be helpful to localize the level of an acute rupture, identify any underlying tendinosis at the site of the rupture, and quantify gapping of tendon ends [53].

Tissue Characterization and Pathophysiology

Histopathology typically does not show markers of inflammation within the tendon in Achilles tendinopathy, making the term "tendinitis" a misnomer [21]. Tendon injury is thought to be caused by a failed healing process resulting in altered tendon structure, neovascularization, and nerve ingrowth [16]. The exact aetiology and pathophysiology of non-insertional Achilles tendinopathy are not fully known and warrant further studies [11]. Histopathological studies of Achilles tendinopathy have been limited to its chronic phase, and it is not clear whether the degenerative features are preceded by an inflammatory phase [2]. In the absence of inflammation in the chronic stage, other factors such as irritation of mechanoreceptors or triggering of nociceptive receptors may cause pain in Achilles tendinopathy [2]. Participants with insertional Achilles tendinopathy had larger tendon diameter, lower echogenicity (indicating degeneration), higher strain, and lower stiffness compared to uninvolved sides and controls [78]. As the factors are uncorrelated, the results of assessment of tendon structure should not be expected to be associated with lower extremity function or biopsychosocial limitations [6]. Bilateral changes in tendon structure are present in patients diagnosed with unilateral insertional or midportion Achilles tendinopathy [51]. The asymptomatic side should not be used as reference in clinical practice for Achilles tendinopathy [51]. The absence of tendinopathic changes in the excised plantaris of 13 patients who clinically improved suggests plantaris involvement with Achilles tendinopathy may not yet be fully understood [34]. Plantaris involvement with Achilles tendinopathy may be a compressive or a frictional phenomenon rather than purely tendinopathic [34].

Risk Factors and Etiology

The body’s response to loading will be influenced by health conditions, drugs, and genetic factors [16]. Identifying risk factors associated with Achilles tendon disorders has a high clinical relevance regarding the development and implementation of prevention strategies and programs [19]. Additional research is required to improve our understanding of the causative factors in Achilles tendinopathy [33].

Treatment

Non-Operative

Achilles tendinosis is a degenerative process that can be treated conservatively with great success [4]. Nonoperative treatment is effective in approximately 50% to 70% of cases [46]. The natural history of the condition is typically a long protracted course where management focuses on physiotherapy [14]. However, 40% of patients report ongoing pain even after five years of therapy [14]. Initial nonsurgical treatment consists of a period of rest, activity modification, and the use of heel lifts with or without immobilization in a walking boot [21]. Long-term use of an ankle-foot orthosis to neutralize the Achilles tendon can be considered as an alternative to surgery if other nonsurgical treatments have been ineffective [21].

Physical therapy with a focus on eccentric strengthening has shown efficacy for the nonsurgical treatment of insertional and noninsertional Achilles tendinopathy [21]. Heavy-load eccentric strengthening has demonstrated the highest success rate for nonoperative treatment of noninsertional Achilles tendinopathy [46]. Both traditional eccentric training and heavy slow resistance training yield positive, equally good, lasting clinical results in patients with Achilles tendinopathy [65]. Heavy slow resistance training is associated with greater patient satisfaction after 12 weeks compared to eccentric training, but not after 52 weeks [65]. Eccentric training was found to be effective in reducing pain in male patients but may be significantly less effective in females [115]. Symptomatic females suffering Achilles tendinopathy do not benefit as much as symptomatic males from 12 weeks of eccentric training [43]. A randomized clinical trial demonstrates that reducing tendon compression (e.g., limiting ankle dorsiflexion) during rehabilitation for insertional Achilles tendinopathy leads to improved clinical outcomes and higher patient satisfaction [63].

Extracorporeal shock wave therapy (ESWT) improves pain and functional outcomes in patients with Achilles tendinopathy compared to other nonsurgical treatments [15]. Shock wave therapy is an effective treatment for chronic noninsertional Achilles tendinopathy [60]. ESWT can improve the symptoms of Achilles tendinopathy, and patients with insertional Achilles tendinopathy who had greater sports activity levels had better therapeutic responses than nonsports-active patients after 5-year follow-up [49]. Current evidence for nonoperative treatment specific for insertional Achilles tendinopathy favors ESWT or the combined treatment of ESWT plus eccentric exercises [86]. Superior subjective clinical outcomes together with a lower failure rate were maintained for >1 year in the noninsertional Achilles tendinopathy cohort compared with the insertional cohort following ESWT [25]. Topical glyceryl trinitrate significantly reduced pain with activity and at night, improved functional measures, and improved outcomes in patients with Achilles tendinopathy [90].

There is no proof that platelet-rich plasma (PRP) injections can enhance patient functional and clinical outcomes for Achilles tendinopathy [31]. PRP is no more effective than placebo for treating Achilles tendinopathy and should not be used for this indication until new, large, high-quality RCTs upend current knowledge [66]. Both platelet-rich plasma (PRP) and autologous adipose-derived stromal vascular fraction (SVF) are safe and effective treatments for Achilles tendinopathy [59]. Both PRP and SVF were safe, effective treatments for recalcitrant Achilles tendinopathy [84].

Operative

Indications: A small subgroup of recalcitrant cases of Achilles tendon disorders may benefit from surgical intervention [8]. Surgical management is indicated for patients in whom conservative treatment of at least 6 months has failed for noninsertional Achilles tendinopathy [10]. Surgical procedures for insertional Achilles tendinopathy are indicated only after failure of conservative treatment [37].

Surgical Approach / Technique: In terms of the surgical treatment of midportion Achilles tendinopathy, no definite recommendations can be made [41]. Surgical treatment usually is successful for insertional Achilles tendinopathy, although no single method or approach appears to be more beneficial than others [55]. The central tendon-splitting approach has gained popularity for insertional Achilles tendinopathy because of its direct approach to the area of pathology [55]. The endoscopic SpeedBridge procedure can be considered an effective and minimally invasive option for the treatment of insertional Achilles tendinopathy [40]. For noninsertional Achilles tendinopathy, less invasive operative options include percutaneous longitudinal tenotomies in the area of degeneration and stripping of the anterior aspect of the tendon to free adhesions [46]. Multiple percutaneous longitudinal tenotomies for chronic Achilles tendinopathy in runners is a safe, low-cost approach that is effective in the long term [32]. Isolated gastrocnemius recession has shown good results for noninsertional Achilles tendinopathy in patients with a gastrocnemius contracture, prior to consideration of a tendon débridement [46]. For moderate to severe noninsertional Achilles tendinopathy, open excision of the degenerated tendon tissue with tubularization has had good results [46]. In extensive noninsertional disease, reconstruction procedures have excellent results and remain the gold standard but are accompanied by significant recovery times and potential complications [10]. Gastrocnemius recession is becoming more popular as an alternative surgical treatment for noninsertional Achilles tendinopathy with less morbidity and good results [10]. Endoscopic debridement of ventral paratenon adhesions has been reported to yield good results and shortened recovery for noninsertional Achilles tendinopathy [10].

For more than 50% degenerative involvement of the Achilles tendon, débridement with a flexor hallucis longus (FHL) tendon transfer is recommended [46]. MRI evidence of significant involvement (diffuse thickening of the tendon without a focal area of disease) indicates the need for FHL transfer in noninsertional Achilles tendinopathy [46]. Most literature supports the use of flexor hallucis longus tendon transfers for surgically treated patients with extensive noninsertional disease (>50% of the tendon volume) [10]. Similar outcomes have been reported with flexor digitorum longus transfers for extensive noninsertional Achilles tendinopathy [10]. If the tendon gap is under 2 cm, an end-to-end repair can be completed along with FHL transfer for noninsertional Achilles tendinopathy [46]. If the tendon gap is 2 to 5 cm, V-Y advancement is considered for noninsertional Achilles tendinopathy [46]. If the tendon gap is greater than 5 cm, a turndown procedure or allograft is used to bridge the gap for noninsertional Achilles tendinopathy [46].

In early disease of insertional Achilles tendinopathy, treatment for retrocalcaneal bursitis by removing the Haglund deformity does not necessarily accompany tendon debridement [37]. Recalcitrant retrocalcaneal bursitis without tendinosis can be treated with open or endoscopic calcaneal exostectomy [37]. A dorsal closing wedge calcaneal osteotomy technique has been described to decompress the tuberosity impingement in insertional Achilles tendinopathy [37]. In later stages of insertional Achilles tendinopathy, traditional techniques with tendon debridement, calcaneal exostectomy, with or without augmentation with tendon transfers are often required [37]. Open techniques for insertional Achilles tendinopathy require large incisions with significant wound complications and prolonged recovery [37]. Similar success has been reported for insertional Achilles tendinopathy through endoscopic techniques [37]. Gastrocnemius release is an effective treatment option in the management of patients with Achilles tendinopathy who have gastrocnemius contracture and have previously failed to respond adequately to non-operative treatment [91]. Isolated gastrocnemius lengthening in insertional and noninsertional tendinopathy has reported success, but patients exhibit continued plantarflexion weakness 18 months after this procedure when compared with controls [37].

Other Considerations: Alfredson H, Spang C, Forsgren S reported that unilateral surgical treatment for patients with midportion Achilles tendinopathy may result in bilateral recovery [17]. Baltes TP, Zwiers R, Wiegerinck JI, van Dijk CN published a systematic review on surgical treatment for midportion Achilles tendinopathy [17]. Bedi HS, Jowett C, Ristanis S, et al. reported on plantaris excision and ventral parateninous scraping for Achilles tendinopathy in an athletic population [17]. Beyer R, Kongsgaard M, Kjaer BH, et al. compared heavy slow resistance versus eccentric training as treatment for Achilles tendinopathy [17]. de Cesar Netto C, Chinanuvathana A, Fonseca LFD, et al. reported outcomes of flexor digitorum longus (FDL) tendon transfer in the treatment of Achilles tendon disorders [17]. Ettinger S, Razzaq R, Waizy H, et al. described operative treatment of the insertional Achilles tendinopathy through a transtendinous approach [17]. Georgiannos D, Lampridis V, Vasiliadis A reported on the treatment of insertional Achilles pathology with dorsal wedge calcaneal osteotomy in athletes [17]. Gross CE, Hsu AR, Chahal J, Holmes Jr GB published a systematic review of injectable treatments for noninsertional Achilles tendinosis [17]. Gurdezi S, Kohls-Gatzoulis J, Solan MC reported results of proximal medial gastrocnemius release for Achilles tendinopathy [17]. Hedgewald KW, Doyle MD, Todd NW, Rush SM described a minimally invasive approach to Achilles tendon pathology [17]. Hunt KJ, Cohen BE, Davis H, et al. conducted a prospective, randomized study on surgical treatment of insertional Achilles tendinopathy with or without flexor hallucis longus transfer [17]. Indino C, D’Ambrosi R, Usuelli FG reviewed biologics in the treatment of Achilles tendon pathologies [17]. Irwin TA published a current concepts review on insertional Achilles tendinopathy [17]. Kang S, Thordarson DB, Charlton TP discussed insertional Achilles tendinitis and Haglund’s deformity [17]. Kearney R, Costa ML published a systematic review on insertional Achilles tendinopathy management [17]. Kiewiet NJ, Holthusen SM, Bohay DR, Anderson JG reported on gastrocnemius recession for chronic noninsertional Achilles tendinopathy [17]. Krogh T, Ellingsen T, Christensen R evaluated ultrasound guided injection therapy of Achilles tendinopathy with PRP or saline [17]. Leduc S, Walling AK described a posterior midline approach for treatment of Achilles calcific insertional tendinopathy [17]. Lohrer H, Davis S, Nauck T published a systematic review on surgical treatment for Achilles tendinopathy [17]. Lui TH reported on the treatment of chronic noninsertional Achilles tendinopathy with endoscopic Achilles debridement and flexor hallucis longus transfer [17]. Lui TH, Lo CY, Siu YC described minimally invasive and endoscopic treatment of Haglund syndrome [17]. Maffulli N, Del Buono A, Testa V, et al. reported on the safety and outcome of surgical debridement of insertional Achilles tendinopathy using a transverse (Cincinnati) incision [17]. McCormack JR, Underwood FB, Slaven EJ, Cappaert TA conducted a randomized controlled trial comparing eccentric exercise versus eccentric exercise and soft tissue treatment (Astym) in the management of insertional Achilles tendinopathy [17]. McGarvey WC, Palumbo RC, Baxter DE, et al. described insertional Achilles tendinosis surgical treatment through a central tendon splitting approach [17]. Molund M, Lapinskas SR, Nilsen FA reported on clinical and functional outcomes of gastrocnemius recession for chronic Achilles tendinopathy [17]. Monto RR discussed platelet rich plasma treatment for chronic Achilles tendinosis [17]. Nawoczenski DA, Barske H, Tome J, et al. reported on isolated gastrocnemius recession for Achilles tendinopathy strength and functional outcomes [17]. Nawoczenski DA, DiLiberto FE, Cantor MS, et al. reported on ankle power and endurance outcomes following isolated gastrocnemius recession for Achilles tendinopathy [17]. Akoh CC, Phisitkul P described a minimally invasive and endoscopic approach for the treatment of noninsertional Achilles tendinopathy [17]. Barg A, Ludwig T discussed surgical strategies for the treatment of insertional Achilles tendinopathy [17]. Bussin ER, Cairns B, Bovard J, et al. conducted a randomized controlled trial evaluating the short term analgesic effect of topical diclofenac on chronic Achilles tendon pain [17]. Chimenti RL, Cychosz CC, Hall MM, et al. published a current concepts review update on insertional Achilles tendinopathy [17]. de Jong S, de Vos RJ, Weir A, et al. reported on one-year follow-up of platelet-rich plasma treatment in chronic Achilles tendinopathy [17]. de Jong S, van den Berg C, de Vos RJ, et al. reported on the incidence of midportion Achilles tendinopathy in the general population [17]. de Vos RJ, Weir A, Tol JL, et al. reported no effects of PRP on ultrasonographic tendon structure and neovascularisation in chronic midportion Achilles tendinopathy [17]. de Vos RJ, Weir A, van Schie HTM, et al. conducted a randomized controlled trial on platelet-rich plasma injection for chronic Achilles tendinopathy [17]. Bulstra GH, van Rheenen TA, Scholtes VA evaluated radiographic evaluation of Haglund’s deformity [17]. No differences were noted in the 1st and 2nd metatarsal head pressures when compared with the unaffected foot after single incision FHL transfer [10]. Schon et al. prospectively reported significant improvement in visual analogue scale (VAS) scores, Short Form Health Survey (SF-36) physical scores, Ankle Osteoarthritis Scale, and performance of a single-leg heel rise at 24 months after Achilles debridement and FHL transfer [10]. In a small series of runners treated with open procedures for insertional Achilles tendinopathy, 67% were able to return to the same level of sport at 8 months after an exostectomy [37]. In a small series of runners treated with open procedures for insertional Achilles tendinopathy, 78% were able to return to the same level of sport at an average of 10 months after reconstruction procedures [37].

Complications

Surgical Complications

Wound complications: Open surgical techniques for insertional Achilles tendinopathy require large incisions and are associated with significant wound complications [37]. Minimally invasive techniques for chronic Achilles tendon ruptures may result in a lower wound complication incidence compared to conventional open procedures [116].

Thromboembolism: Repair of chronic Achilles ruptures has a high incidence of venous thromboembolism [39].

Tendon rupture: Achilles tendon rupture is a reported complication following surgical exploration for tendinopathy, occurring at five weeks post-operatively during isometric loading [50].

Functional deficits: Isolated gastrocnemius lengthening for insertional and noninsertional tendinopathy results in continued plantarflexion weakness 18 months after the procedure [37]. Flexor hallucis longus tendon transfer is associated with decreased hallux pressure and FHL weakness [10].

Other Considerations: Secondary reconstruction for Achilles tendinopathy can be performed safely in obese patients without increasing short-term postoperative complication rates [35].

Post-Rupture Complications

Heterotopic ossification: Heterotopic ossification occurs relatively frequently after Achilles tendon ruptures but appears to have no adverse effects on functional outcomes [101].

Tendon elongation: The ruptured Achilles tendon elongates for 6 months after surgical repair regardless of early or late weightbearing in combination with ankle mobilization [52].

Treatment Outcomes and Limitations

ESWT limitations: ESWT outcomes for insertional Achilles tendinopathy are inferior to those for noninsertional Achilles tendinopathy, with a higher failure rate in the insertional cohort [25].

Sex-specific response: Symptomatic females suffering from Achilles tendinopathy do not benefit as much as symptomatic males from 12 weeks of eccentric training [43].

Recovery

Non-Operative Recovery

Other Considerations: While exercises improve function in the majority of patients, 40% of patients report ongoing pain even after five years of therapy [14]. Symptom duration did not influence baseline measures of tendon health in patients with Achilles tendinopathy [133].

Operative Recovery

Other Considerations: Achilles tendon rupture following surgical exploration for tendinopathy has not been previously reported; the rupture occurred at five weeks post-operatively during isometric loading, though the exact cause remains unexplained [50].

Key Evidence

• [L5] The mainstay of treatment for all Achilles tendon diagnoses is nonoperative. [1] (10.2106/jbjs.o.00002)
• [L5] [2] (10.2106/00004623-200211000-00024)
• [L5] Non-insertional Achilles tendinopathy is often managed conservatively with excellent clinical results, while insertional Achilles tendinopathy management is improved by recognizing coexisting pathologies and evolving surgical approaches. [3] (10.1302/0301-620x.95b10.31881)
• [Paper] Achilles tendinosis is a degenerative process that can be treated conservatively with great success or surgically for refractory cases, though there is currently a lack of consensus regarding the best treatment options. [4] (10.1016/j.csm.2020.05.001)
• [L2] There was no association between the tendon structure and symptoms. [5] (10.1177/0363546515605077)
• [L4] As the factors are uncorrelated, the results of assessment of, for example, tendon structure should not be expected to be associated with lower extremity function or biopsychosocial limitations. [6] (10.1186/s12891-022-05702-1)
• [L4] Surgical intervention gave superior patient reported outcome compared with non-surgical treatment for patients affected by a chronic Achilles tendon rupture. [7] (10.1186/s12891-026-09890-y)
• [L5] Most cases of Achilles tendon disorders are successfully treated nonoperatively, while a small subgroup of recalcitrant cases may benefit from surgical intervention. [8] (10.1177/03635465020300022501)
• [L4] The majority of patients with Achilles tendinopathy fully recovered in regard to both symptoms and function when treated with exercise alone. [9] (10.1177/0363546510384789)
• [L5] The exact aetiology and pathophysiology of non-insertional Achilles tendinopathy are not fully known and warrant further studies. [11] (10.1136/jisakos-2017-000164)
• [Paper] Our Dutch multidisciplinary guideline on Achilles tendinopathy provides six modules developed according to the standards of the Dutch Federation of Medical Specialists. [13] (10.1136/bjsports-2020-103867)
• [L2] ESWT improves pain and functional outcomes in patients with Achilles tendinopathy compared to other nonsurgical treatments. [15] (10.1177/2325967120903430)
• [L1] The wait-and-see strategy was ineffective for the management of chronic recalcitrant tendinopathy of the main body of the Achilles tendon. [18] (10.1177/0363546506295940)
• [L3] Identifying risk factors associated with Achilles tendon disorders has a high clinical relevance regarding the development and implementation of prevention strategies and programs. [19] (10.1007/s00402-012-1476-9)
• [L4] Achilles tendinopathy causes not only pain and symptoms in patients but also apparent impairments in various aspects of lower leg muscle-tendon function as measured with the test battery. [22] (10.1007/s00167-006-0150-6)
• [L5] The ICON meetings could be an appropriate platform to initiate a new widely supported agreement on diagnostic criteria for Achilles tendinopathy. [23] (10.1136/bjsports-2020-102863)
• [L4] The revised terminology for Achilles tendon-related disorders based on anatomic location, symptoms, clinical findings and histopathology is used by the majority of orthopedic surgeons and is increasingly used in the literature. [24] (10.1007/s00167-021-06566-z)
• [L3] Superior subjective clinical outcomes together with a lower failure rate were maintained for >1 year in the noninsertional Achilles tendinopathy cohort compared with the insertional cohort, calling into question the long-term benefit of ESWT for patients with insertional Achilles tendinopathy. [25] (10.1177/23259671241265330)
• [L2] Measures of tendon morphology and mechanical properties appear to be associated with patient-reported symptoms and calf muscle function for patients with Achilles tendinopathy. [27] (10.1177/2325967120917271)
• [L5] Until now, an evidence based algorithm for the (conservative) management of midportion Achilles tendinopathy is unknown. [28] (10.1007/s00167-011-1415-2)
• [L2] Open surgery for midportion Achilles tendinopathy is safe and effective in medium term. [29] (10.1007/s00167-014-3232-x)
• [L1] There is no proof that PRP injections can enhance patient functional and clinical outcomes for Achilles tendinopathy. [31] (10.3390/jcm12030995)
• [L4] This approach to the management of midportion Achilles tendinopathy is safe, has a low cost, and is effective in the long term. [32] (10.1177/0363546513494356)
• [L3] Additional research is required to improve our understanding of the causative factors in Achilles tendinopathy. [33] (10.1177/0363546509332250)
• [L4] The absence of tendinopathic changes in the excised plantaris of 13 patients who clinically improved suggests plantaris involvement with Achilles tendinopathy may not yet be fully understood and supports the concept that this may be a compressive or a frictional phenomenon rather than purely tendinopathic. [34] (10.1177/2325967116673978)
• [L3] Our findings suggest that secondary reconstruction for Achilles tendinopathy can be done safely in obese patients without increasing short-term postoperative complication rates. [35] (10.5435/jaaos-d-25-00746)
• [Paper] Surgery for insertional Achilles tendinopathy led to good functional outcomes and satisfactory return to sports when the surgical care was tailored to the degree of tendon involvement. [36] (10.1016/j.otsr.2018.05.003)
• [L4] [38] (10.1136/bjsports-2017-098161)
• [L5] This procedure can be considered an effective and minimally invasive option in the arsenal of insertional Achilles tendinopathy treatment. [40] (10.1016/j.eats.2021.05.014)
• [L4] In terms of the surgical treatment of midportion Achilles tendinopathy, no definite recommendations can be made. [41] (10.1007/s00167-014-3407-5)
• [L4] Magnetic resonance imaging techniques can be used as an adjunct to clinical evaluation by monitoring morphologic effects in clinical treatment studies of Achilles tendinopathy. [42] (10.1177/0363546504263148)
• [L3] Symptomatic females suffering Achilles tendinopathy do not benefit as much as symptomatic males from 12 weeks of eccentric training. [43] (10.1007/s00167-009-1006-7)
• [L3] The results of this study provide a rationale for current clinical approaches to management of Achilles tendinopathy, whereby repetitive mechanical loading may impart a positive benefit through reduced compliance of the musculotendinous unit. [44] (10.1177/0363546510366234)
• [L4] Grey-scale ultrasonography in combination with colour Doppler examination has identified neovascularisation in the area with tendinosis in patients with painful chronic Achilles tendinosis. [48] (10.1007/s001670000189)
• [L3] ESWT can improve the symptoms of Achilles tendinopathy, and patients with IAT who had greater sports activity levels had better therapeutic responses than nonsports-active patients after 5-year follow-up. [49] (10.1177/2325967119898118)
• [Case_report] Achilles tendon rupture following surgical exploration for tendinopathy has not been previously reported; the rupture occurred at five weeks post-operatively during isometric loading, though the exact cause remains unexplained. [50] (10.1186/1471-2474-8-19)
• [L3] These results stress the importance of monitoring both symptomatic and asymptomatic tendon structures and in addition highlight that the asymptomatic side should not be used as reference in clinical practice. [51] (10.1007/s00167-019-05495-2)
• [L1] Differences in rehabilitation loading pattern in the initial 8 weeks after the repair of an Achilles tendon rupture did not measurably alter the outcome. [52] (10.1177/0363546518781826)
• [L4] The use of a free gastrocnemius aponeurosis flap to treat chronic ruptures and reruptures of the Achilles tendon rendered a good overall subjective and objective outcome in the majority of patients. [54] (10.1007/s00167-008-0492-3)
• [L3] [57] (10.1007/s00402-014-2030-8)
• [L1] Both PRP and SVF are safe and effective treatments for Achilles tendinopathy. [59] (10.1177/2325967116s00128)
• [L3] Shock wave therapy is an effective treatment for chronic noninsertional Achilles tendinopathy. [60] (10.1177/0363546507309674)
• [L4] US + CD directly, and clinical assessment indirectly, can detect a close by located plantaris tendon in a high proportion of patients with midportion Achilles tendinopathy. [62] (10.1186/s12891-016-0955-5)
• [L1] This randomised clinical trial demonstrates that reducing tendon compression (eg, limiting ankle dorsiflexion) during rehabilitation for insertional Achilles tendinopathy leads to improved clinical outcomes and higher patient satisfaction. [63] (10.1136/bjsports-2024-109138)
• [L1] Both traditional eccentric training and heavy slow resistance training yield positive, equally good, lasting clinical results in patients with Achilles tendinopathy, with the latter tending to be associated with greater patient satisfaction after 12 weeks but not after 52 weeks. [65] (10.1177/0363546515584760)
• [L1] PRP is no more effective than placebo for treating Achilles tendinopathy and should not be used for this indication until new, large, high-quality RCTs upend current knowledge. [66] (10.1097/corr.0000000000003478)
• [L2] It is not possible to draw conclusions regarding the best surgical treatment for insertional Achilles tendinopathy. [67] (10.1007/s00167-012-2219-8)
• [L5] [70] (10.1177/2325967119879052)
• [L1] [71] (10.1530/eor-2025-0095)
• [L5] Insertional Achilles tendinopathy results from a complex interplay of mechanical loads, vascular impairment, and inflammatory responses, where understanding these mechanisms is essential to optimizing conservative treatments, refining surgical approaches, and developing novel therapeutic strategies. [74] (10.1016/j.jisako.2025.100867)
• [L3] Participants with insertional achilles tendinopathy had larger tendon diameter, lower echogenicity (indicating degeneration), higher strain, and lower stiffness compared to uninvolved sides and controls. [78] (10.2519/jospt.2014.5369)
• [L4] [81] (10.1016/j.fas.2012.12.006)
• [L1] Both PRP and SVF were safe, effective treatments for recalcitrant Achilles tendinopathy. [84] (10.1007/s00167-017-4479-9)
• [L2] Current evidence for nonoperative treatment specific for insertional Achilles tendinopathy favors ESWT or the combined treatment of ESWT plus eccentric exercises. [86] (10.1186/s13018-021-02370-0)
• [L2] There was no statistically significant difference in favor of one imaging modality over the others, but MRI revealed the highest overall diagnostic accuracy for the diagnosis of both insertional and midportion Achilles tendinopathy. [87] (10.1177/23259671211006826)
• [L4] This is the first study to use the continuum model of tendon pathology to develop an USI- based criteria to diagnose tendinopathy. [88] (10.1136/bmjsem-2019-000699)
• [L1] Topical glyceryl trinitrate significantly reduced pain with activity and at night, improved functional measures, and improved outcomes in patients with Achilles tendinopathy. [90] (10.2106/00004623-200405000-00005)
• [L4] The results of this review suggest gastrocnemius release to be an effective treatment option in the management of patients with Achilles tendinopathy, who have gastrocnemius contracture and have previously failed to respond adequately to non-operative treatment. [91] (10.1007/s00167-022-07039-7)
• [L4] MRI-derived measures of Achilles tendon fat content may be able to distinguish xanthomas from control and tendinopathic tissue. [93] (10.1186/s12891-021-04494-0)
• [L3] [96] (10.1007/s00167-012-2203-3)
• [L3] Heterotopic ossification occurs relatively frequently after Achilles tendon ruptures but appears to have no adverse effects on functional outcomes. [101] (10.1097/corr.0000000000001085)
• [L1] Until future high-quality RCTs show a clear clinical benefit, PRP should not be used to treat Achilles tendinopathy. [104] (10.1097/corr.0000000000003349)
• [L3] Minimally invasive technique may result in a lower wound complication incidence and provide better early functional recovery and return to moderate-intensity exercise time than the conventional open procedure in treating chronic Achilles tendon ruptures. [116] (10.1007/s00167-022-07167-0)
• [L4] Neovascularisation is part of the pathophysiological process in tendinopathy of the Achilles tendon, patellar tendon, and upper extremity tendinopathies. [117] (10.1186/1749-799x-3-18)
• [L4] Complications correlate with age, and intra-tendon MRI abnormalities are frequent but likely represent non-pathologic cicatricial remodeling. [119] (10.1016/j.otsr.2013.03.021)
• [L2] We identified a lower peak ankle inversion moment, a lower peak ankle external rotation angle and a greater running volume as significant predictors of the onset of Achilles tendinopathy. [122] (10.1136/bjsports-2025-110260)
• [L5] [125] (10.1007/s00167-011-1535-8)
• [L4] Ultrasonographic follow up of patients with mid-portion painful chronic Achilles tendinosis treated with eccentric calf muscle training showed a localised decrease in tendon thickness and a normalised tendon structure in most patients. [127] (10.1136/bjsm.2001.000284)
• [L3] Achilles tendon thickness of more than 6.1 mm and intratendinous abnormality of over 48.8% were confirmed to be diagnostic cutoff values for IAT. [128] (10.1186/s13018-025-06036-z)
• [L4] Interposed tissue between the tendon stumps is suitable for repair of chronic Achilles tendon rupture if preoperative MRI shows a thickened fusiform-shaped Achilles tendon with diffuse intratendinous high-signal alterations throughout. [129] (10.1177/0363546506295939)
• [L4] A computerized 3-D seed-growing technique to monitor and evaluate the volume of the Achilles tendon and mean intratendinous signal using MR imaging shows an overall excellent reliability regarding inter- as well as intra-observer reliability. [130] (10.1007/s00167-004-0546-0)
• [L5] The Kager fat pad does not remain static during ankle range of motion, but deforms and its pressure also changes. [131] (10.1007/s00167-019-05585-1)
• [L3] Symptom duration did not influence baseline measures of tendon health. [133] (10.1177/23259671231164956)
• [L5] The plantaris tendon inserting directly into the calcaneus resulted in significantly greater differential motion compared with the Achilles tendon. [138] (10.1177/0363546517745291)
• [L2] UTC of tendon structure, Achilles tendon thickness, and foot posture did not significantly contribute to the prediction of Achilles tendinopathy. [139] (10.1177/0363546517750854)
• [L3] Compared with healthy controls, runners currently symptomatic with AT or MTSS have a longer duration of eversion but not greater excursion or velocity of eversion. [142] (10.1177/0363546517708193)

See Also

• Achilles tendon rupture
• Ankle osteoarthritis

References

[1] Everything Achilles: Knowledge Update and Current Concepts in Management. The Journal of Bone and Joint Surgery-American Volume. 2015. DOI: 10.2106/jbjs.o.00002

[2] ACHILLES TENDINOPATHY. The Journal of Bone and Joint Surgery-American Volume. 2002. DOI: 10.2106/00004623-200211000-00024

[3] Achilles tendinopathy. The Bone & Joint Journal. 2013. DOI: 10.1302/0301-620x.95b10.31881

[4] Achilles Tendinosis Injuries—Tendinosis to Rupture (Getting the Athlete Back to Play). Clinics in Sports Medicine. 2020. DOI: 10.1016/j.csm.2020.05.001

[5] The Tendon Structure Returns to Asymptomatic Values in Nonoperatively Treated Achilles Tendinopathy but Is Not Associated With Symptoms. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515605077

[6] Data driven model of midportion achilles tendinopathy health created with factor analysis. BMC Musculoskeletal Disorders. 2022. DOI: 10.1186/s12891-022-05702-1

[7] Incidence, reason for treatment delay and patient-reported outcome of patients affected by a chronic Achilles tendon rupture in a Swedish population. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09890-y

[8] Achilles Tendon Disorders in Athletes. The American Journal of Sports Medicine. 2002. DOI: 10.1177/03635465020300022501

[9] The Majority of Patients With Achilles Tendinopathy Recover Fully When Treated With Exercise Alone. The American Journal of Sports Medicine. 2010. DOI: 10.1177/0363546510384789

[10] Campbell S Operative Orthopaedics 4 Volume Set. MULTIPLE Z-PLASTY RELEASE OF A CONGENITAL RING > NONINSERTIONAL ACHILLES TENDINOPATHY.

[11] Achilles tendinopathy – pathophysiology: state of the art. Journal of ISAKOS. 2018. DOI: 10.1136/jisakos-2017-000164

[13] Dutch multidisciplinary guideline on Achilles tendinopathy. British Journal of Sports Medicine. 2021. DOI: 10.1136/bjsports-2020-103867

[14] Featured specialty lead: Mr Mike Carmont What is new about Achilles tendinopathy?. 2014.

[15] Efficacy of Extracorporeal Shock Wave Therapy for Achilles Tendinopathy: A Meta-analysis. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120903430

[16] Orthopaedic Knowledge Update Sports Medicine 6. Foot and Ankle Rehabilitation > Achilles Tendinopathy.

[17] Campbell S Operative Orthopaedics 4 Volume Set. MULTIPLE Z-PLASTY RELEASE OF A CONGENITAL RING > ACHILLES TENDON.

[18] Eccentric Loading, Shock-Wave Treatment, or a Wait- and-See Policy for Tendinopathy of the Main Body of Tendo Achillis. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546506295940

[19] Analysis of hereditary and medical risk factors in Achilles tendinopathy and Achilles tendon ruptures: a matched pair analysis. Archives of Orthopaedic and Trauma Surgery. 2012. DOI: 10.1007/s00402-012-1476-9

[20] Aaos Comprehensive Orthopaedic Review 3. Tendon Disorders of the Foot and Ankle > I. Achilles Tendon Disorders.

[21] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Foot and Ankle Reconstruction > Achilles Tendinopathy.

[22] Evaluation of lower leg function in patients with Achilles tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0150-6

[23] Diagnosing Achilles tendinopathy is like delicious spaghetti carbonara: it is all about key ingredients, but not all chefs use the same recipe. British Journal of Sports Medicine. 2020. DOI: 10.1136/bjsports-2020-102863

[24] Increasing consensus on terminology of Achilles tendon‐related disorders. Knee Surgery, Sports Traumatology, Arthroscopy. 2021. DOI: 10.1007/s00167-021-06566-z

[25] Outcomes After Extracorporeal Shockwave Therapy for Chronic Noninsertional Achilles Tendinopathy Compared With Chronic Insertional Achilles Tendinopathy: A Retrospective Review. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/23259671241265330

[27] Tendon Morphology and Mechanical Properties Are Associated With the Recovery of Symptoms and Function in Patients With Achilles Tendinopathy. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120917271

[28] Injection treatment for chronic midportion Achilles tendinopathy: do we need that many alternatives?. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1415-2

[29] Open surgical treatment for chronic midportion Achilles tendinopathy: faster recovery with the soleus fibres transfer technique. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3232-x

[31] The Efficacy of Platelet-Rich Plasma Injection Therapy in the Treatment of Patients with Achilles Tendinopathy: A Systematic Review and Meta-Analysis. Journal of Clinical Medicine. 2023. DOI: 10.3390/jcm12030995

[32] Multiple Percutaneous Longitudinal Tenotomies for Chronic Achilles Tendinopathy in Runners. The American Journal of Sports Medicine. 2013. DOI: 10.1177/0363546513494356

[33] No Influence of Age, Gender, Weight, Height, and Impact Profile in Achilles Tendinopathy in Masters Track and Field Athletes. The American Journal of Sports Medicine. 2009. DOI: 10.1177/0363546509332250

[34] Plantaris Excision Reduces Pain in Midportion Achilles Tendinopathy Even in the Absence of Plantaris Tendinosis. Orthopaedic Journal of Sports Medicine. 2016. DOI: 10.1177/2325967116673978

[35] Comparison of Early Postoperative Outcomes and Reimbursement Metrics in Obese Versus Nonobese Patients Undergoing Secondary Reconstruction for Achilles Tendinopathy. Journal of the American Academy of Orthopaedic Surgeons. 2025. DOI: 10.5435/jaaos-d-25-00746

[36] Functional outcomes and return to sports after surgical treatment of insertional Achilles tendinopathy: Surgical approach tailored to the degree of tendon involvement. Orthopaedics & Traumatology: Surgery & Research. 2018. DOI: 10.1016/j.otsr.2018.05.003

[37] Campbell S Operative Orthopaedics 4 Volume Set. MULTIPLE Z-PLASTY RELEASE OF A CONGENITAL RING > INSERTIONAL ACHILLES TENDINOPATHY.

[38] Chronic inflammation is a feature of Achilles tendinopathy and rupture. British Journal of Sports Medicine. 2017. DOI: 10.1136/bjsports-2017-098161

[39] Campbell S Operative Orthopaedics 4 Volume Set. ACHILLES TENDON AUGMENTATION OF SUPERIOR PERONEAL RETINACULUM REPAIR > RUPTURE OF ACHILLES TENDON.

[40] Endoscopic SpeedBridge Procedure for the Treatment for Insertional Achilles Tendinopathy: The Snake Technique. Arthroscopy Techniques. 2021. DOI: 10.1016/j.eats.2021.05.014

[41] Treatment of midportion Achilles tendinopathy: an evidence‐based overview. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3407-5

[42] Eccentric Training of the Gastrocnemius-Soleus Complex in Chronic Achilles Tendinopathy Results in Decreased Tendon Volume and Intratendinous Signal as Evaluated by MRI. The American Journal of Sports Medicine. 2004. DOI: 10.1177/0363546504263148

[43] Gender and eccentric training in Achilles mid‐portion tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2009. DOI: 10.1007/s00167-009-1006-7

[44] Mechanical Properties of the Achilles Tendon Aponeurosis Are Altered in Athletes With Achilles Tendinopathy. The American Journal of Sports Medicine. 2010. DOI: 10.1177/0363546510366234

[45] Campbell S Operative Orthopaedics 4 Volume Set. MULTIPLE Z-PLASTY RELEASE OF A CONGENITAL RING > DISORDERS OF THE ACHILLES TENDON.

[46] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > 5. Noninsertional Achilles tendinopathy.

[48] Neovascularisation in Achilles tendons with painful tendinosis but not in normal tendons: an ultrasonographic investigation. Knee Surgery, Sports Traumatology, Arthroscopy. 2001. DOI: 10.1007/s001670000189

[49] Therapeutic Response of Extracorporeal Shock Wave Therapy for Insertional Achilles Tendinopathy Between Sports-Active and Nonsports-Active Patients With 5-Year Follow-up. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967119898118

[50] Achilles tendon rupture following surgical management for tendinopathy: a case report. BMC Musculoskeletal Disorders. 2007. DOI: 10.1186/1471-2474-8-19

[51] Bilateral changes in tendon structure of patients diagnosed with unilateral insertional or midportion achilles tendinopathy or patellar tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2019. DOI: 10.1007/s00167-019-05495-2

[52] The Ruptured Achilles Tendon Elongates for 6 Months After Surgical Repair Regardless of Early or Late Weightbearing in Combination With Ankle Mobilization: A Randomized Clinical Trial. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518781826

[53] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Foot and Ankle Reconstruction > Achilles Tendon Rupture.

[54] A new surgical method to treat chronic ruptures and reruptures of the Achilles tendon. Knee Surgery, Sports Traumatology, Arthroscopy. 2008. DOI: 10.1007/s00167-008-0492-3

[55] Orthopaedic Knowledge Update Sports Medicine 6. Ankle and Foot Injuries and Other Disorders > Achilles Tendon Disorders > Insertional Achilles Tendinopathy.

[57] Results of operative treatment for recalcitrant retrocalcaneal bursitis and midportion Achilles tendinopathy in athletes. Archives of Orthopaedic and Trauma Surgery. 2014. DOI: 10.1007/s00402-014-2030-8

[59] Treatment of Achilles Tendinopathy with Autologous Adipose-derived Stromal Vascular Fraction. Orthopaedic Journal of Sports Medicine. 2016. DOI: 10.1177/2325967116s00128

[60] High-Energy Extracorporeal Shock Wave Therapy as a Treatment for Chronic Noninsertional Achilles Tendinopathy. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546507309674

[62] How to diagnose plantaris tendon involvement in midportion Achilles tendinopathy - clinical and imaging findings. BMC Musculoskeletal Disorders. 2016. DOI: 10.1186/s12891-016-0955-5

[63] Effectiveness of reducing tendon compression in the rehabilitation of insertional Achilles tendinopathy: a randomised clinical trial. British Journal of Sports Medicine. 2025. DOI: 10.1136/bjsports-2024-109138

[65] Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515584760

[66] Editor’s Spotlight/Take 5: Is Platelet-rich Plasma Effective in Treating Achilles Tendinopathy? A Meta-analysis of Randomized Clinical Trials. Clinical Orthopaedics & Related Research. 2025. DOI: 10.1097/corr.0000000000003478

[67] Treatment for insertional Achilles tendinopathy: a systematic review. Knee Surgery, Sports Traumatology, Arthroscopy. 2012. DOI: 10.1007/s00167-012-2219-8

[70] Chinese Consensus on Insertional Achilles Tendinopathy. Orthopaedic Journal of Sports Medicine. 2019. DOI: 10.1177/2325967119879052

[71] The effect of different non-drug therapies on Achilles tendinopathy: a systematic review and network meta-analysis. EFORT Open Reviews. 2026. DOI: 10.1530/eor-2025-0095

[74] Pathophysiology and healing of insertional Achilles tendinopathy: Current concepts. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.100867

[78] Altered Tendon Characteristics and Mechanical Properties Associated With Insertional Achilles Tendinopathy. Journal of Orthopaedic & Sports Physical Therapy. 2014. DOI: 10.2519/jospt.2014.5369

[81] What is the best clinical test for Achilles tendinopathy?. Foot and Ankle Surgery. 2013. DOI: 10.1016/j.fas.2012.12.006

[84] Intratendinous adipose-derived stromal vascular fraction (SVF) injection provides a safe, efficacious treatment for Achilles tendinopathy: results of a randomized controlled clinical trial at a 6-month follow-up. Knee Surgery, Sports Traumatology, Arthroscopy. 2017. DOI: 10.1007/s00167-017-4479-9

[86] Nonoperative treatment of insertional Achilles tendinopathy: a systematic review. Journal of Orthopaedic Surgery and Research. 2021. DOI: 10.1186/s13018-021-02370-0

[87] Multimodal Ultrasound Versus MRI for the Diagnosis and Monitoring of Achilles Tendinopathy: A Prospective Longitudinal Study. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/23259671211006826

[88] Staging achilles tendinopathy using ultrasound imaging: the development and investigation of a new ultrasound imaging criteria based on the continuum model of tendon pathology. BMJ Open Sport & Exercise Medicine. 2020. DOI: 10.1136/bmjsem-2019-000699

[90] Topical Glyceryl Trinitrate Treatment of Chronic Noninsertional Achilles Tendinopathy. The Journal of Bone & Joint Surgery. 2004. DOI: 10.2106/00004623-200405000-00005

[91] Gastrocnemius release is an effective management option for Achilles tendinopathy: a systematic review. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07039-7

[93] Can Achilles tendon xanthoma be distinguished from Achilles tendinopathy using Dixon method MRI? A cross-sectional exploratory study. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04494-0

[96] Arguments for an increasing differentiation towards fibrocartilaginous components in midportion Achilles tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2012. DOI: 10.1007/s00167-012-2203-3

[101] Heterotopic Ossification After an Achilles Tendon Rupture Cannot Be Prevented by Early Functional Rehabilitation: A Cohort Study. Clinical Orthopaedics & Related Research. 2020. DOI: 10.1097/corr.0000000000001085

[104] Is Platelet-rich Plasma Effective in Treating Achilles Tendinopathy? A Meta-analysis of Randomized Clinical Trials. Clinical Orthopaedics & Related Research. 2024. DOI: 10.1097/corr.0000000000003349

[108] Campbell S Operative Orthopaedics 4 Volume Set. ULNAR COLLATERAL LIGAMENT REPAIR WITH AN INTERNAL BRACE > RUPTURE OF ACHILLES TENDON > ANATOMY AND PATHOPHYSIOLOGY.

[109] Campbell S Operative Orthopaedics 4 Volume Set. ULNAR COLLATERAL LIGAMENT REPAIR WITH AN INTERNAL BRACE > AAOS Recommendations: Achilles Tendon Ruptures.

[110] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Foot and Ankle > Achilles Tendon.

[115] Orthopaedic Knowledge Update Sports Medicine 6. Ankle and Foot Injuries and Other Disorders > Achilles Tendon Disorders > Overuse Injuries.

[116] Endoscopic‐assisted locking block modified Krackow technique combined with a V‐Y flap for chronic Achilles tendon rupture. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07167-0

[117] The role of tendon microcirculation in Achilles and patellar tendinopathy. Journal of Orthopaedic Surgery and Research. 2008. DOI: 10.1186/1749-799x-3-18

[119] Treatment of chronic Achilles tendon rupture by shortening suture and free sural triceps aponeurosis graft. Orthopaedics & Traumatology: Surgery & Research. 2013. DOI: 10.1016/j.otsr.2013.03.021

[122] Biomechanical insights into Achilles tendinopathy risk and protection in runners: a large prospective study 4HAIE. British Journal of Sports Medicine. 2025. DOI: 10.1136/bjsports-2025-110260

[125] Mid‐portion Achilles tendinopathy: why painful? An evidence‐based philosophy. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1535-8

[127] Eccentric training in patients with chronic Achilles tendinosis: normalised tendon structure and decreased thickness at follow up. British Journal of Sports Medicine. 2004. DOI: 10.1136/bjsm.2001.000284

[128] Correlations between insertional Achilles tendinopathy and haglund’s deformity: MRI and radiographic findings. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-025-06036-z

[129] Reconstruction of Chronic Achilles Tendon Rupture with the use of Interposed Tissue between the Stumps. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546506295939

[130] Reliability in the assessment of tendon volume and intratendinous signal of the Achilles tendon on MRI: a methodological description. Knee Surgery, Sports Traumatology, Arthroscopy. 2004. DOI: 10.1007/s00167-004-0546-0

[131] Pressure changes in the Kager fat pad at the extremes of ankle motion suggest a potential role in Achilles tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2019. DOI: 10.1007/s00167-019-05585-1

[133] Effect of Symptom Duration on Injury Severity and Recovery in Patients With Achilles Tendinopathy. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671231164956

[138] Differential Motion and Compression Between the Plantaris and Achilles Tendons: A Contributing Factor to Midportion Achilles Tendinopathy?. The American Journal of Sports Medicine. 2017. DOI: 10.1177/0363546517745291

[139] The Role of the Vascular and Structural Response to Activity in the Development of Achilles Tendinopathy: A Prospective Study. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546517750854

[142] Biomechanical Factors Associated With Achilles Tendinopathy and Medial Tibial Stress Syndrome in Runners. The American Journal of Sports Medicine. 2017. DOI: 10.1177/0363546517708193