Skip to content

Clinicians › Knee

Quadriceps and patellar tendon rupture

53 citationsUpdated Sep 2026

Overview

Quadriceps and patellar tendon ruptures compromise the knee extensor mechanism, necessitating adequate repair to restore function [2]. Early surgical management is generally required to achieve functional recovery [6]. Operative treatment is indicated for all extensor tendon ruptures where extensor mechanism function is compromised, soft tissues are adequate for healing, and the patient is fit for surgery [20]. Missed diagnoses or delayed treatment result in challenging reconstructions with less predictable outcomes [2]. While specific surgical techniques vary based on lesion type and chronicity [6], acute repair of quadriceps tendon ruptures provides better knee function compared to patellar tendon rupture repair [7]. Good to excellent outcomes are reported in both groups following surgical treatment [1], with early primary repair of patellar tendon ruptures allowing early, controlled motion and yielding good functional and objective results [4].

Surgical exposure typically employs an extensile straight midline incision, extending from the inferior patella to 5 cm proximal to the quadriceps tendon rupture or from the superior patella to the tibial tubercle for patellar tendon ruptures [20]. The joint is irrigated to remove hematoma and assess the tear, patella, and articular surfaces [20]. Repair techniques include debridement and suture passage for acute avulsions, end-to-end approximation for midsustance ruptures, or reinforcement via the Scuderi technique or quadriceps turndown flap if the repair is tenuous [20]. A braided nonabsorbable relaxing suture tensioned at 30 degrees of flexion has been used to reinforce repairs, permitting early active motion and brace-free ambulation at 6 weeks with 100% good and excellent results in a series of 20 quadriceps repairs [20]. Most tendon avulsion repairs are sufficiently strong that secondary stress-relieving devices are not required [20].

Tendinopathy of the patellar or quadriceps tendon affects active individuals, particularly those in jumping sports, with patellar tendinopathy common in adolescents and young adults and quadriceps tendinopathy in middle-aged and older adults [23]. The condition presents with insidious pain and swelling, often limiting athletic performance [23]. Nonsurgical intervention is the mainstay of treatment, consisting of activity modification, progressive flexibility and eccentric strengthening exercises, taping or strap use, and NSAIDs [23]. Corticosteroid injection is contraindicated due to the increased risk of tendon rupture [23]. Surgery is reserved for patients with persistent pain and swelling after nonsurgical treatment has been attempted [23]. Surgical options include débridement of diseased tissue, bone abrasion, drilling, or tendon perforations to stimulate healing, all performed via a standard anterior midline incision [23].

Anatomy & Pathophysiology

Soft Tissue Anatomy

The extensor mechanism comprises the quadriceps tendon, medial and lateral retinacula, patella, and patellar tendon [110]. The quadriceps muscle complex consists of the vastus lateralis, vastus medialis, rectus femoris, and vastus intermedius [110]. The vastus lateralis inserts on the patella at an approximately 30-degree angle relative to the longitudinal axis of the femur [110]. The vastus medialis longus inserts proximally on the patella at an angle of 15 to 18 degrees relative to the femoral long axis, while the vastus medialis obliquus inserts more distally at an angle of 50 to 55 degrees [110]. Rectus femoris fibers run 7 to 10 degrees medially relative to the femoral long axis in the coronal plane [110]. The vastus intermedius lies deep to the rectus femoris and inserts directly into the superior base of the patella [110].

Previous studies describe a trilaminar organization of the quadriceps tendon, with the rectus femoris tendon superficial, the vastus medialis and lateralis tendons in the middle, and vastus intermedius fibers deep [110]. The insertion reflects an intricate blending of all tendon fibers at the superior patella [110]. The patellar retinaculum and iliotibial band function as secondary extensors of the knee [110]. The retinaculum forms from the continuation of the deep investing fascia lata in the thigh and is reinforced by aponeurotic fibers from both the vastus medialis and lateralis [110]. Both medial and lateral retinacula insert directly into the proximal tibia [110].

The medial patellofemoral ligament is an extracapsular continuation of the deep retinacular surface of the VMO, extending from the superior medial border of the patella to bone just anterior to the medial collateral ligament on the medial epicondyle [110]. It contributes 50% to 60% of the total restraining force of the medial patellar stabilizers [110]. The ligament has a fan-shaped configuration running from the upper medial margin of the patella to a femoral insertion posterosuperior to the epicondyle and just distal to the adductor tubercle [110]. Cadaveric dissections reveal the medial patellofemoral ligament to be 58.8 ± 4.7 mm in length, 12 ± 3.1 mm in width, and inclined 15.9 ± 5.6 degree proximally [110].

The patellar tendon originates from the apex of the patella proximally and inserts into the tibial tubercle distally [110]. Its average length is 5 cm [110]. The tendon forms primarily from a continuation of the central fibers of the rectus femoris tendon [110]. It is reinforced at its tibial insertion medially and laterally by the extensor retinaculum and the iliotibial tract [110]. The patellar tendon receives its blood supply from the infrapatellar fat pad and from the retinaculum through the medial and lateral inferior geniculate arteries [61].

Pathophysiology & Mechanism of Injury

Rupture of the patellar or quadriceps tendon generally occurs with eccentric loading of the knee extensor mechanism, often when the foot is planted and the knee is slightly bent [29]. Less commonly, injuries occur with a direct blow to the tendon when the extensor mechanism is under tension [29]. These are typically low-energy injuries [36]. The mechanism typically involves a forceful quadriceps contraction against a fixed or sudden load of full body weight with the knee in a flexed position, resulting in eccentric loading [36]. In general, healthy tendons do not rupture [96]. Under normal conditions, tensile overload of the extensor mechanism usually leads to fracture of the patella, considered the weakest link in the extensor mechanism [96]. In a rabbit model, between 50% and 75% of tendon fibers had to be transected to result in rupture under forces greater than those seen under physiologic conditions [96].

Patellar tendon ruptures secondary to indirect trauma have been considered the end stage of long-standing chronic tendon degeneration secondary to repetitive microtrauma [96]. Biopsy specimens of spontaneously ruptured tendons reveal pathologic findings that are degenerative in nature, including hypoxic tendinopathy, mucoid degeneration, tendolipomatosis, and calcifying tendinopathy [96]. Ruptures may occur in the absence of pathologic tendon degeneration [96]. Prodromal symptoms were present in 46% of professional football players prior to patellar tendon rupture [96]. Younger patients with chronic jumper's knee that resulted in tendon rupture had more severe symptoms than older patients, suggesting more advanced degeneration is required to weaken younger healthier tendons [96].

Both patellar tendon and quadriceps tendon ruptures typically occur at the tendon attachment to the patella [29]. Underlying chronic degeneration often is present and is characterized by angiofibroblastic tendinosis, mucoid degeneration, and pseudocyst formation at the attachment of tendon to bone [29]. The quadriceps tendon has been described as having two to four distinct layers [29]. The deep fibers of the patellar tendon attachment have a tenuous blood supply [23]. Affected tissue in patellar tendinopathy may demonstrate fibrinoid necrosis, angiofibroblastic change, or mucoid degeneration and disorganized collagen structure [23]. The medial portion of the patellar tendon often demonstrates thickening compared with the rest of the tendon [23]. Patellar or quadriceps tendinopathy is characterized by disorganized collagen structure visualized on MRI by thickening of the tendon and signal intensity changes [55].

The most common injury pattern for patellar tendon rupture is a proximal sided rupture [61]. Midsubstance ruptures or distal avulsions are also possible [61]. A complete patellar tendon rupture occurs in 97% of cases reported in the literature [66]. Patellar tendon ruptures usually occur at the pole of the patella [66].

Epidemiology & Risk Factors

Rupture of the patellar tendon is most common in patients younger than 40 years [29]. Rupture of the quadriceps tendon is most common in patients older than 40 years [29]. Patellar tendon ruptures occur more commonly in patients less than 40 years old, while quadriceps tendon ruptures occur more commonly in patients greater than 40 years of age [36]. Patellar tendon ruptures are most common in the third and fourth decades of life [61]. Patellar tendon ruptures are more common in males than females [61]. Patellar tendon ruptures are less prevalent than quadriceps tendon ruptures [61].

Risk factors for patellar tendon rupture include systemic lupus erythematosus, rheumatoid arthritis, chronic renal disease, diabetes mellitus, steroid injection, and preexisting patellar tendinopathy [61]. Patients who sustain quadriceps tendon ruptures may have underlying conditions that predispose them to injury, such as obesity, diabetes mellitus, hyperparathyroidism, rheumatoid arthritis, systemic lupus erythematosus, hyperbetalipoproteinemia, hemangioendothelioma, chronic renal failure, or gout [29]. Anabolic steroid use and local corticosteroid injection into the tendon are associated with both types of tendon ruptures [29]. Quadriceps tendon ruptures occur more commonly in patients with systemic disease or degenerative changes [36]. Numerous reports of simultaneous bilateral quadriceps tendon rupture have been published and include patients with systemic illness and obesity [36]. Bilateral rupture of the patellar tendon can occur but is less frequent [36].

Patellar tendon ruptures account for a very small part of complications occurring after total knee arthroplasty, estimated in less than 1% of the cases registered [31]. Acute patellar tendon injury after total knee arthroplasty is quite infrequent given their traumatic source needing enormous forces of impact [31]. Chronic tear from tissue degeneration for different causes is relatively common after total knee arthroplasty [31].

Associated Injuries

ACL tears have accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture [36]. A 30% incidence of intra-articular associated injuries was found in all patients with patellar tendon rupture [15]. The most common associated injuries in the patellar tendon rupture group were ACL ruptures (18%) and medial meniscus tears (18%) [15]. Eight patients had either a medial tear, lateral tear or both meniscuses torn (24%) in a study of patellar tendon ruptures [15]. The average age at time of rupture was 36 for patellar tendon ruptures and 51 for quadriceps tendon rupture patients [15]. A 5.6 to 1 male to female ratio was found in a study of knee extensor mechanism ruptures [15].

Classification

Epidemiology and Demographics

Patellar tendon ruptures demonstrate a strong male predominance, with a documented male-to-female ratio of 5.6 to 1 [15]. In the pediatric population, this injury is rare, representing 7% of pediatric patients who sustain acute traumatic injury to the knee extensor mechanism [30]. The demographic profile of tendinopathy varies by location: patellar tendinopathy, or jumper’s knee, occurs most frequently in adolescents and young adults, whereas quadriceps tendinopathy affects middle-aged and older adults [23].

Associated Injuries

Intra-articular associated injuries occur in 30% of all patients with patellar tendon rupture [15]. Specifically, meniscal pathology is common, with eight patients exhibiting either a medial tear, lateral tear, or both meniscuses torn, representing 24% of the patellar tendon rupture group [15]. In the setting of multi-ligamentous knee injury (MLKI), patients with a concomitant patellar tendon rupture experience worse functional outcomes compared to those without this additional injury [22].

Pathoanatomy

Patellar tendon ruptures following ACL graft harvest typically present in a proximal-medial/distal-lateral or entirely distal pattern [17].

Diagnostic Classification Schemes

Blazina: This classification applies to patellar or quadriceps tendinopathy and consists of three stages: Stage 1 (pain after activity), Stage 2 (pain during and after activity), and Stage 3 (pain that limits function during an activity) [23].

Popkin and Golman: This system classifies partial patellar tendon tears based on tendon anterior-posterior thickness and the percentage of tendon torn [53]. The classification demonstrates high interrater and inter-rater reliability [53]. Surgical débridement and possible repair are recommended for grade 4 partial patellar tendon tears that fail 6 months of conservative treatment according to this classification [53].

Clinical Presentation

Mechanism and Epidemiology

Patellar tendon ruptures are more common in males, with a 5.6 to 1 male-to-female ratio reported in one study [15]. The typical mechanism involves an eccentric overload on a flexed knee, such as landing from a jump or taking a forceful step while descending stairs [29]. In a series of National Football League players, this specific mechanism was present in 21 of 24 injuries [57]. Less commonly, rupture occurs during a forceful quadriceps contraction when taking off for a jump [29], or following a direct blow to the tendon while the extensor mechanism is under tension [29].

History and Symptoms

Patients often report a history of pain consistent with underlying tendon degeneration [29]. Prodromal signs may include pain, atrophy, and tenderness around the distal or proximal patellar pole, or a history of Osgood–Schlatter disease or jumper's knee [36]. In the NFL series, 11 of 24 players complained of anterior knee pain before rupture, with 10 diagnosed with patellar tendinosis and 1 with patellofemoral pain [57]. The acute injury is dramatic, characterized by a tearing or popping sensation, acute pain, swelling, and an inability to bear weight [36, 54]. The associated pain and disability are profound and may distract both the patient and clinician from other sites of injury [15].

Physical Examination

Physical examination for a complete rupture demonstrates tenderness at the injury site, hematoma, and a palpable defect in the tendon [29]. A traumatic hemarthrosis is common after extensor mechanism injuries [36]. Immediately after injury, a defect may be palpable at the level of the rupture [36]. If the tear is complete and the patella has migrated proximally, a palpable defect may be observed [54]. When the diagnosis is delayed, the tendon defect may not be palpable due to consolidation of the hematoma and early scar formation [36].

The hallmark of patellar tendon injury is weakness or loss of active extension, which may be difficult to appreciate in an acutely painful and swollen knee [54]. Patients with a complete rupture of either the patellar or quadriceps tendon cannot extend the knee against resistance or perform a straight leg raise [29]. The key to diagnosing an extensor mechanism injury is the lack of active knee extension or the inability to maintain the passively extended knee against gravity [36]. Typically, some degree of extensor lag is present when compared with the uninjured limb [36].

In incomplete ruptures, or in patients with a complete quadriceps tendon rupture but an intact retinaculum, the ability to perform a straight leg raise against gravity may be uncompromised [29]. Most commonly, patellar tendon ruptures extend completely through the retinacular tissue, resulting in complete loss of knee extension [36]. Quadriceps tendon ruptures may not involve as much retinacular tissue, allowing some extension to remain possible [36].

Imaging

Radiographs of the knee after patellar tendon rupture demonstrate patella alta, particularly with the knee flexed [29]. In cases of neglected patellar tendon rupture, lateral radiographs confirm the proximal position of the patella compared with the uninjured side [21]. Radiographs obtained after quadriceps tendon rupture demonstrate patella baja and sometimes show bony fragments in the region of the rupture [29]. MRI can be helpful when the diagnosis is uncertain, particularly when differentiating between a partial and a complete rupture of a tendon [29].

Associated Injuries

ACL tears have accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture and should be sought during the initial evaluation or with MRI [36]. A 30% incidence of intra-articular associated injuries was found in all patients with patellar tendon rupture in one study [15]. In the setting of multi-ligamentous knee injury, patients who have a concomitant patellar tendon rupture have worse functional outcomes compared to those without [22].

Investigations

Physical Examination: Acute hemarthrosis or a palpable defect at the tendon level may be identified on physical examination in patients with extensor mechanism ruptures [15]. Careful assessment of patella mobility, combined with a history of symptoms occurring during knee flexion, is key to distinguishing patellar dislocation from other pathologies [13].

MRI: Magnetic resonance imaging clearly delineates acute ruptures of the patellar ligament and avulsion fractures of the patella, aiding diagnosis when radiographs are inconclusive due to small bone fragments [129]. MRI and ultrasonography are reliable and interchangeable methods only for evaluating noninjured patellar tendons [133]. Partial-thickness tears are located posterior or posteromedially in the proximal patellar tendon, with tendon thickness >8.8 mm strongly correlated with the presence of a tear [47]. The quadriceps tendon is significantly thicker than the patellar tendon at 1, 2, and 4 cm from the patella in both males and females based on preoperative MRI [65]. Preoperative MRI predicted the required quadriceps tendon length for ACL reconstruction, but 37% of patients lacked an adequate quadriceps tendon length [159]. A quadriceps tendon shorter than 60 mm required the addition of a patellar bone plug autograft in anterior cruciate ligament reconstruction [159].

Other Considerations: The average age at time of rupture was 36 years for patellar tendon ruptures and 51 years for quadriceps tendon ruptures [15]. Patellar tendon ruptures have been documented to be more common in males, with a 5.6 to 1 male to female ratio observed in the study population [15]. Eight patients in the patellar tendon rupture group had either a medial tear, lateral tear, or both meniscuses torn (24%) [15]. The patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on serial MRI evaluations [18]. Extensive calcification of the patellar tendon may form after removal of the central third for grafting, yet it can persist for more than eleven years without causing any complaint about range of motion or pain [19].

Treatment

Non-Operative

Nonsurgical management is indicated for partial ruptures of the patellar or quadriceps tendon when no disruption of the extensor mechanism is present [29]. It is also indicated for patients who are unable to tolerate surgery due to poor overall medical condition [29]. Incomplete ruptures are usually managed conservatively without surgical intervention if full active extension is present on physical examination [114]. Nearly all patients with partial extensor mechanism tears underwent initial nonoperative management [147].

Nonsurgical management consists of an initial period of immobilization in a knee brace followed by progressive range-of-motion and strengthening exercises beginning approximately 6 weeks after injury [29]. The limb is initially immobilized with the knee in full extension for 4 to 6 weeks, after which protected range of motion and strengthening are begun [114]. Initially, flexion of greater than 90 degrees is avoided to reduce stress on the tendon during nonoperative management [114]. Restrictions are removed once the patient achieves good quadriceps muscle control and is able to perform a straight-leg raise without discomfort [114].

For patellar or quadriceps tendinopathy, initial treatment consists of activity modification [23]. Progressive flexibility and eccentric strengthening exercises follow initial activity modification for tendinopathy [23]. Taping to aid proprioception and patellar tracking or using an infrapatellar strap can be helpful for tendinopathy [23]. NSAIDs can be beneficial for the treatment of tendinopathy [23]. Surgery for tendinopathy is reserved for patients who continue to have pain and swelling of the tendon after a nonsurgical treatment regimen has been attempted [23]. Arthroscopic patellar release translates into sustained pain relief and functional improvement over a long-term follow-up in athletes with chronic symptomatic patellar tendinopathy [69]. Treatment for patellar tendinopathy continues to evolve, with biologic and less-invasive ultrasound-based treatments showing promise, and surgical intervention providing reliable outcomes [157].

Nonsurgical management of a complete quadriceps or patellar tendon rupture generally yields poor results with long-term disability in gait and weakness [114]. Untreated complete ruptures will result in ambulation with a stiff-knee gait or circumduction to allow the foot to clear the ground during the swing phase of gait [114]. Patients with untreated complete ruptures will also complain of knee buckling and difficulty in climbing stairs [114].

Operative

Indications: Surgery is indicated for a complete rupture of the patellar or quadriceps tendon [29]. Early surgery (within the first 2 weeks after injury) is recommended for complete ruptures [29]. An early repair within 2 to 3 weeks of injury is the only factor that has been associated with better outcomes [44]. Patellar tendon rupture has a good prognosis if diagnosis and surgical treatment is early [14]. Missed diagnoses and delayed treatment lead to challenging reconstructions with less predictable results [2]. In the setting of total knee arthroplasty, non-operative treatment often results in critical functional impairment; therefore, surgery has become the standard of care [31]. Primary repair may be acceptable in an early or partial rupture after total knee arthroplasty, but has very poor results in the management of chronic complete patellar tendon disruptions [31]. Primary repair is a reasonable approach for patients with a distal avulsion of the patellar tendon after total knee arthroplasty since the tendon can be stapled securely back to the tubercle and heal completely with a full functional recovery [31].

Surgical Approach / Technique: Early surgical management is generally needed for quadriceps and patellar tendon tears to restore function, with specific techniques varying based on the lesion type and chronicity [6]. For acute quadriceps tendon avulsion from the superior pole of the patella, treatment involves debridement of the tendon followed by the passage of two heavy nonabsorbable sutures into the tendon [20]. Three parallel drill holes are created from superior to inferior through the patella for quadriceps tendon avulsion repair [20]. Sutures are passed through the drill holes and tied at the inferior patella and the retinacular tissue is repaired for quadriceps tendon avulsion [20]. Full-thickness flaps are elevated medially and laterally to identify the apex of the retinacular tears, if present [20]. A midsustance quadriceps tendon rupture can be repaired with end-to-end approximation of the tendon rupture [20]. If the quadriceps tendon repair is tenuous, the Scuderi technique or quadriceps turndown flap has been described as a method to reinforce the surgical repair [20]. The quadriceps turndown flap is folded distally over the rupture/repair and sutured into place [20]. Several authors have suggested techniques for reinforcing the repair using wire, Dacron tape, or suture [20]. The authors felt the relaxing suture reinforced the repair and allowed early active motion and brace-free ambulation at 6 weeks [20].

For acute patellar tendon avulsion from the inferior pole of the patella, treatment involves debridement of the tendon followed by the passage of two heavy nonabsorbable sutures into the tendon [102]. Three parallel drill holes are created from inferior to superior in the patella for patellar tendon avulsion repair [102]. Sutures are passed through the drill holes and tied at the superior pole of the patella for patellar tendon avulsion repair [102]. The medial and lateral retinacular tears are identified and repaired during patellar tendon avulsion repair [102]. A cerclage or reinforcement suture or wire is recommended for most cases of patellar tendon avulsion repair [102]. The cerclage wire or suture is performed by drilling a transverse tunnel 1 cm posterior to the tibial tubercle and passing heavy nonabsorbable suture or wire through the hole [102]. The wire or suture is brought proximally and passed under the quadriceps tendon close to the superior border of the patella and tensioned at 30 degrees of flexion [102]. The knee is flexed to 90 degrees to test the integrity of the repair after patellar tendon avulsion repair [102]. No complications and 100% good and excellent results were reported in 30 patients with patellar tendon rupture treated with transosseous sutures and a braided nonabsorbable suture [102]. The authors felt this reinforced the repair and allowed early active motion and brace-free ambulation at 6 weeks [102].

Hamstring autograft can be utilized for patellar tendon repair [102]. The semitendinosus tendon is harvested with an open tendon stripper leaving the insertion intact for hamstring autograft augmentation [102]. The proximal aspect of the semitendinosus tendon is passed through a transverse drill hole in the patella and sutured to the distal lateral retinaculum or patellar tendon [102]. This method has been shown to lead to less gap formation at the repair in biomechanical studies [102]. The patellar tendon suture line is then reinforced with absorbable sutures, the wound is closed in layers, and a well-padded dressing is applied [102]. A hinged knee brace is applied with the knee in full extension after patellar tendon repair [102]. A midsustance patellar tendon tear is more difficult to repair as the quality of tissue may be compromised and caution should be observed to prevent shortening of the tendon and creating patella baja with placement of the sutures [102]. The most common method of repair for midsustance patellar tendon tears involves simple end-to-end repair, with or without a reinforcing cerclage suture of wire or nonabsorbable suture material or tape [102]. A distal patellar tendon rupture from the tibial tubercle is the least common pattern [102]. A suture repair through bone tunnels with semitendinosus and gracilis augmentation as described for late reconstruction is recommended for distal patellar tendon ruptures [102].

Although initially used only in comorbid patients with increased risk of wound healing complications, arthroscopic suture repair is now used in every case of acute quadriceps tendon rupture by the authors [40]. A combined repair technique for patellar tendon rupture using two suture anchors and three transosseous sutures may serve as a practical and effective option for proximal patellar tendon ruptures [25]. Suture anchor fixation of the quadriceps tendon is a viable option in the setting of rupture after total knee arthroplasty, offering advantages such as less soft tissue dissection and avoidance of violation of the patella tendon [64]. Immediate primary repair of the patellar tendon and delayed reconstruction of the ACL is the preferred treatment option for simultaneous rupture [8].

Outcomes and Complications: Most series have reported between 70% and 100% good to excellent results for acute patellar tendon repair [44]. The majority of patients who undergo early primary repair achieve a functional range of motion and normal quadriceps strength [44]. Persistent quadriceps muscle atrophy commonly occurs after early primary repair, but has not been correlated with loss of strength [44]. No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical outcome [44]. Siwek and Rao reviewed 25 patients treated within 7 days and found that 96% had good to excellent results while only two of the six patients with a delayed repair had excellent results [44]. Siwek and Rao noted a greater degree of persistent quadriceps atrophy in patients treated with delayed repair [44]. Hsu et al. reviewed 35 traumatic patellar tendon ruptures treated acutely with primary repair and a neutralization wire and reported 20 excellent (57%) and 10 (29%) good results [44]. The majority of the patients in the Hsu et al. series had sustained the injury on a motorcycle and one-third of the patients had multiple injuries which the authors concluded may have contributed to the slightly lower success rate observed [44]. Larsen and Lund performed a radiographic analysis of patellar congruence in a series of patients who underwent operative repair of acute patellar tendon ruptures [44]. Seven of 10 patients demonstrated incongruity on the Merchant and lateral radiographs in the Larsen and Lund series [44]. Patients with residual patellofemoral symptoms all had incongruity but the majority were asymptomatic in the Larsen and Lund series [44]. They concluded that articular incongruity may not be the only cause of persistent knee pain in patients who undergo patellar tendon repair [44]. West et al. demonstrated no complications and excellent results in 30 patellar tendon ruptures treated with transosseous sutures and a braided nonabsorbable relaxing suture placed through the quadriceps tendon and retinaculum and around the distal patella tensioned at 30 degrees of flexion [44]. The authors then instituted range of motion from 0 to 55 degrees at 7 days and weaned the patient to brace-free ambulation at 6 weeks [44]. Good to excellent outcomes were revealed in both quadriceps and patellar tendon rupture groups [1].

Chronic or Neglected Ruptures: Chronic or neglected patellar tendon ruptures present significant operative challenges [44]. The unopposed pull of the quadriceps muscles can result in significant contraction of the extensor mechanism in chronic ruptures [44]. Early series recommended preoperative traction to overcome the contracted quadriceps muscle so that the tendon ends could be reapproximated [44]. To our knowledge, there have been no large series evaluating the outcomes after reconstruction of a chronic patellar tendon rupture [44]. Isolated case reports have described different techniques and grafts including autogenous or allogenic grafts when local tissue is unavailable for chronic ruptures [44]. Results have generally been less satisfactory compared to acute repair for chronic patellar tendon ruptures [44]. Repair of chronic patellar tendon rupture can be complicated by proximal retraction of the patella and by insufficient tissue for repair [29]. Retraction can be addressed by surgical dissection and mobilization of the quadriceps tendon [29]. Tendon augmentation can be performed with a hamstring autograft passed through tibial and patellar drill holes, a central quadriceps tendon–patellar bone autograft, a contralateral bone–patellar tendon–bone autograft, or an allograft [29]. Augmentation with wire, nonabsorbable tape, or heavy suture also can be considered for chronic patellar tendon rupture repair [29]. Chronic quadriceps tendon ruptures also can be complicated by proximal migration of the tendon stump, which requires débridement and mobilization of the tendon [29]. Following débridement and mobilization, the tendon can be augmented with autograft or allograft tissue and secured to bone for chronic quadriceps tendon ruptures [29].

Surgical reconstruction of chronic patellar tendon ruptures using contralateral bone-tendon-bone graft was a safe and viable option that improves clinical and functional outcomes compared to presurgical function [32]. Hamstring tendon reconstruction of chronic patellar tendon rupture provided good functional recovery and return to preinjury daily activities [27]. The hamstring tendon autograft is a safe, effective, and acceptable choice for patellar tendon reconstruction [59]. The use of hamstring tendons is a good option for the management of chronic quadriceps tendon tears, providing good results despite a 7-month delay between injury and surgery [46]. Reconstruction of patellar tendon rupture has a much lower complication rate than repair, supporting the recommendation of patellar tendon reconstruction in both early and late presentation stages after total knee arthroplasty [3]. The medial gastrocnemius transposition flap may be best suited for the treatment of complicated disruptions of the extensor mechanism in patients who have had a failed repair of the quadriceps or who have a rupture of the patellar ligament and poor soft-tissue coverage, poor healing potential, inadequate patellar bone stock, or an exposed prosthesis with loss of the extensor mechanism [5]. Busfield et al. and Jaureguito et al. successfully performed on extended medial gastrocnemius rotational flap reconstruction of the extensor mechanism which was found to provide simultaneous soft tissue coverage and an efficient reinforcement of the ruptured tendon while also achieving successful salvage of a failed extensor mechanism allograft previously implanted in patients who presented small area of compromise [31]. The possibility of rupture of a patellar ligament allograft in the future must be considered because one would not expect that a patellar ligament allograft would be vascularized fully after two years [26].

Complications

Associated Injuries

Intra-articular associated injuries occur in 30% of patients with patellar tendon rupture [15]. Specifically, 24% of patients in one study presented with medial tears, lateral tears, or both menisci torn [15]. The significant pain and disability associated with extensor mechanism ruptures can distract both the patient and the clinician from identifying other sites of injury [15]. When simultaneous rupture of the patellar tendon and ACL occurs, immediate primary repair of the patellar tendon followed by delayed reconstruction of the ACL is the preferred treatment option [8].

Diagnostic and Treatment Errors

Misdiagnosis is a recognized complication in neglected cases; three patients with neglected patellar tendon ruptures were initially misdiagnosed, with two cases identified as patellar dislocations and the third as generalized ligamentous laxity with patellar instability [21]. A repair of a neglected patellar tendon rupture failed soon after surgery when no external splint was used, leaving the patient untreated for a further 11 months [21]. Careful physical examination of patella mobility and a history of symptoms occurring in knee flexion are key diagnostic factors to distinguish conditions like lateral meniscus displacement from patella dislocation [13].

Chronic and Neglected Rupture Complications

Chronic quadriceps tendon ruptures can be complicated by proximal migration of the tendon stump, which requires débridement and mobilization of the tendon [29]. In chronic or neglected patellar tendon ruptures, the unopposed pull of the quadriceps muscles can result in significant contraction of the extensor mechanism [44]. All patients with neglected patellar tendon ruptures demonstrated patella alta, quadriceps muscle atrophy, and weak or absent knee extension [21]. Additionally, all such patients had an extensor lag of greater than 20° with a maximum of 45° [21]. Results for reconstruction of chronic patellar tendon rupture have generally been less satisfactory compared to acute repair [44]. Primary repair has very poor results in the management of chronic complete patellar tendon disruptions after total knee arthroplasty [31].

Post-Operative and Donor Site Complications

Persistent quadriceps muscle atrophy commonly occurs after early primary repair of patellar tendon rupture but has not been correlated with loss of strength [44]. A greater degree of persistent quadriceps atrophy was noted in patients treated with delayed repair of patellar tendon rupture [44]. Seven of 10 patients who underwent operative repair of acute patellar tendon ruptures demonstrated incongruity on Merchant and lateral radiographs [44]. Patients with residual patellofemoral symptoms after patellar tendon repair all had incongruity, but the majority were asymptomatic [44]. Patellar tendon ruptures are rare after ACL graft harvest and typically occur in a proximal-medial/distal-lateral or entirely distal pattern [17]. Bilateral patellar tendon rupture is a rare complication of systemic lupus erythematosus and long-term corticosteroid therapy [127]. The possibility of rupture of a patellar ligament allograft in the future must be considered because full vascularization is not expected after two years [26].

Outcomes and Functional Limitations

Reconstruction of patellar tendon rupture has a much lower complication rate than repair, supporting the recommendation of reconstruction in both early and late presentation stages [3]. Non-operative treatment of patellar tendon rupture after total knee arthroplasty often results in critical functional impairment [31]. Patients with complications after anterior cruciate ligament reconstruction with a patellar tendon autograft may have less difficulty obtaining full knee motion when the graft is harvested from the contralateral knee [48].

Recovery

Acute Repair Outcomes: Good to excellent outcomes are reported in both quadriceps and patellar tendon rupture groups following surgical treatment [1]. The majority of patients who undergo early primary repair of the patellar tendon achieve a functional range of motion and normal quadriceps strength [44]. Persistent quadriceps muscle atrophy commonly occurs after acute patellar tendon repair but has not been correlated with loss of strength [44]. No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical outcome for acute patellar tendon ruptures [44]. Early repair within 2 to 3 weeks of injury is the only factor associated with better outcomes for acute patellar tendon ruptures [44]. In a review of 25 patients treated within 7 days, 96% had good to excellent results, while only two of six patients with delayed repair had excellent results [44]. A greater degree of persistent quadriceps atrophy was noted in patients treated with delayed repair compared to early repair [44]. In a series of 35 traumatic patellar tendon ruptures treated acutely with primary repair and a neutralization wire, 57% had excellent results and 29% had good results [44].

Rehabilitation Protocol: In a series of 30 patellar tendon ruptures treated with transosseous sutures and a braided nonabsorbable relaxing suture, range of motion from 0 to 55 degrees was instituted at 7 days and patients were weaned to brace-free ambulation at 6 weeks [44]. In the same series of 30 patellar tendon ruptures treated with transosseous sutures and a relaxing suture, no complications and excellent results were demonstrated [44].

Other Considerations: Patients with residual patellofemoral symptoms after acute patellar tendon repair all had incongruity, but the majority were asymptomatic [44]. Articular incongruity may not be the only cause of persistent knee pain in patients who undergo patellar tendon repair [44]. Decreases in total minutes played were observed following operative patellar tendon tears in National Basketball Association players [164].

Key Evidence

  • [L3] Good to excellent outcomes were revealed in both quadriceps and patellar tendon rupture groups. [1] (10.1016/j.injury.2015.06.042)
  • [L5] Adequate repair of the quadriceps and patellar tendons is essential for a functional extensor mechanism; missed diagnoses and delayed treatment lead to challenging reconstructions with less predictable results. [2] (10.1007/s11999-013-3396-6)
  • [L4] Reconstruction of patellar tendon rupture has a much lower complication rate than repair, supporting the recommendation of patellar tendon reconstruction in both early and late presentation stages. [3] (10.1016/j.arth.2019.02.046)
  • [L4] Good functional and objective results can be obtained in patellar tendon ruptures repaired early using only a sturdy primary repair that allows early, controlled motion of the knee. [4] (10.1177/03635465990270030601)
  • [L4] It may be best suited for the treatment of complicated disruptions of the extensor mechanism in patients who have had a failed repair of the quadriceps or who have a rupture of the patellar ligament and poor soft-tissue coverage, poor healing potential, inadequate patellar bone stock, or an exposed prosthesis with loss of the extensor mechanism. [5] (10.2106/00004623-199706000-00010)
  • [L4] Early surgical management is generally needed for quadriceps and patellar tendon tears to restore function, with specific techniques varying based on the lesion type and chronicity. [6] (10.1016/j.otsr.2012.12.002)
  • [L3] Acute surgical repair of quadriceps tendon ruptures provides better knee function, in comparison to the surgical restoration of patellar tendon rupture. [7] (10.1016/j.otsr.2018.09.019)
  • [Case_report] Immediate primary repair of the patellar tendon and delayed reconstruction of the ACL is the preferred treatment option. [8] (10.1007/s00167-006-0048-3)
  • [L4] Quadriceps and patellar tendon repairs protected by a relaxing suture were strong enough to safely permit early motion, weightbearing, and brace-free ambulation while producing good and excellent results. [11] (10.1177/0363546507308192)
  • [L4] History of symptoms occurring in knee flexion and careful physical examination of patella mobility are key diagnostic factors. [13] (10.1007/s00167-013-2729-z)
  • [L4] Patellar tendon rupture has a good prognosis if diagnosis and surgical treatment is early. [14] (10.1016/j.otsr.2014.12.017)
  • [L4] [15] (10.1007/s00167-008-0516-z)
  • [L4] Patellar tendon ruptures are rare after ACL graft harvest and typically occur in a proximal-medial/distal-lateral or entirely distal pattern. [17] (10.1177/0363546512449815)
  • [L2] The patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on serial MRI evaluations. [18] (10.1007/s001670050115)
  • [L4] Extensive calcification of the patellar tendon may form after removal of the central third for grafting, yet it can persist for more than eleven years without causing any complaint about range of motion or pain. [19] (10.1007/s00167-003-0424-1)
  • [L4] [21] (10.1177/03635465010290041301)
  • [L4] In the setting of MLKI, patients who have a concomitant patellar tendon rupture have worse functional outcomes compared to those without. [22] (10.1007/s00167-022-07110-3)
  • [L3] This technique may serve as a practical and effective option for proximal patellar tendon ruptures. [25] (10.1186/s12891-025-09018-8)
  • [Case_report] The possibility of rupture of such a graft in the future must be considered because one would not expect that a patellar ligament allograft would be vascularized fully after two years. [26] (10.2106/00004623-199407000-00019)
  • [L4] Hamstring tendon reconstruction of chronic patellar tendon rupture provided good functional recovery and return to preinjury daily activities. [27] (10.2106/jbjs.l.01462)
  • [L4] Patellar tendon rupture is rare in the pediatric population and represents 7% of pediatric patients who sustained acute traumatic injury of the knee extensor mechanism. [30] (10.1016/j.injury.2017.08.069)
  • [L4] [31] (10.1007/s00167-014-3189-9)
  • [L4] Surgical reconstruction of chronic patellar tendon ruptures using contralateral bone-tendon-bone graft was a safe and viable option that improves clinical and functional outcomes compared to presurgical function. [32] (10.1007/s00167-015-3951-7)
  • [L4] Although initially used only in comorbid patients with increased risk of wound healing complications, the authors now use it in every case of acute quadriceps tendon rupture. [40] (10.1016/j.otsr.2016.12.018)
  • [L4] The use of hamstring tendons is a good option for the management of chronic quadriceps tendon tears, providing good results despite a 7-month delay between injury and surgery. [46] (10.1007/s00167-006-0044-7)
  • [L2] Partial-thickness tears are located posterior or posteromedially in the proximal patellar tendon, with tendon thickness >8.8 mm strongly correlated with the presence of a tear. [47] (10.1177/0363546519894333)
  • [L3] Patients with complications after anterior cruciate ligament reconstruction with a patellar tendon autograft may have less difficulty obtaining full knee motion when the graft is harvested from the contralateral knee. [48] (10.1177/0363546510388163)
  • [L5] [53] (10.5435/jaaosglobal-d-24-00060)
  • [L4] [54] (10.1530/eor-22-0021)
  • [L4] [57] (10.1177/0363546511417083)
  • [L4] The hamstring tendon autograft is a safe, effective, and acceptable choice for patellar tendon reconstruction. [59] (10.1007/s00402-014-2080-y)
  • [L4] Suture anchor fixation of the quadriceps tendon is a viable option in the setting of rupture after total knee arthroplasty, offering advantages such as less soft tissue dissection and avoidance of violation of the patella tendon. [64] (10.1016/j.arth.2011.01.006)
  • [L4] The quadriceps tendon is significantly thicker than the patellar tendon at 1, 2, and 4 cm from the patella in both males and females based on preoperative MRI before ACL surgery. [65] (10.1016/j.asmr.2023.04.005)
  • [L4] [66] (10.1016/j.otsr.2011.01.015)
  • [L4] Arthroscopic patellar release translates into sustained pain relief and functional improvement over a long-term follow-up in athletes. [69] (10.1186/s12891-017-1851-3)
  • [Case_report] Bilateral patellar tendon rupture is a rare complication of systemic lupus erythematosus and long-term corticosteroid therapy. [127] (10.1186/s12891-020-03513-w)
  • [Case_report] Magnetic resonance imaging can clearly delineate acute ruptures of the patellar ligament and avulsion fractures of the patella, aiding in diagnosis when radiographs are inconclusive due to small bone fragments. [129] (10.2106/00004623-199511000-00012)
  • [L3] MRI and US are reliable (interchangeable) methods only for evaluating noninjured patellar tendons. [133] (10.1007/s001670000132)
  • [L5] Nearly all patients with partial extensor mechanism tears underwent initial nonoperative management. [147] (10.1016/j.asmr.2024.100944)
  • [L5] Treatment for patellar tendinopathy continues to evolve, with biologic and less-invasive ultrasound-based treatments showing promise, and surgical intervention providing reliable outcomes. [157] (10.1016/j.arthro.2023.09.004)
  • [L3] Although preoperative MRI predicted the required QT length for ACL reconstruction, 37% of patients lacked an adequate QT length, and a QT shorter than 60 mm required the addition of patellar bone. [159] (10.1007/s00167-020-06261-5)
  • [L4] However, decreases in total minutes played were observed following patellar tendon tear. [164] (10.1177/2325967118800479)

See Also

References

[1] Extensor mechanism ruptures of the knee: Differences in demographic data and long-term outcome after surgical treatment. Injury. 2015. DOI: 10.1016/j.injury.2015.06.042

[2] Complications in Brief: Quadriceps and Patellar Tendon Tears. Clinical Orthopaedics & Related Research. 2014. DOI: 10.1007/s11999-013-3396-6

[3] Treatment of Extensor Tendon Disruption After Total Knee Arthroplasty: A Systematic Review. The Journal of Arthroplasty. 2019. DOI: 10.1016/j.arth.2019.02.046

[4] Primary Repair of Patellar Tendon Rupture Without Augmentation. The American Journal of Sports Medicine. 1999. DOI: 10.1177/03635465990270030601

[5] Medial Gastrocnemius Transposition Flap for the Treatment of Disruption of the Extensor Mechanism after Total Knee Arthroplasty. The Journal of Bone & Joint Surgery*. 1997. DOI: 10.2106/00004623-199706000-00010

[6] Acute and old ruptures of the extensor apparatus of the knee in adults (excluding knee replacement). Orthopaedics & Traumatology: Surgery & Research. 2013. DOI: 10.1016/j.otsr.2012.12.002

[7] Better knee function after surgical repair of acute quadriceps tendon rupture in comparison to acute patellar tendon rupture. Orthopaedics & Traumatology: Surgery & Research. 2019. DOI: 10.1016/j.otsr.2018.09.019

[8] Simultaneous rupture of the patellar tendon and the anterior cruciate ligament: a case report and literature review. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0048-3

[11] Early Motion after Quadriceps and Patellar Tendon Repairs. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546507308192

[13] Displacing lateral meniscus masquerading as patella dislocation. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2729-z

[14] Acute traumatic patellar tendon rupture: Early and late results of surgical treatment of 38 cases. Orthopaedics & Traumatology: Surgery & Research. 2015. DOI: 10.1016/j.otsr.2014.12.017

[15] Intra‐articular knee injuries in patients with knee extensor mechanism ruptures. Knee Surgery, Sports Traumatology, Arthroscopy. 2008. DOI: 10.1007/s00167-008-0516-z

[17] Tear Patterns, Surgical Repair, and Clinical Outcomes of Patellar Tendon Ruptures After Anterior Cruciate Ligament Reconstruction With a Bone–Patellar Tendon–Bone Autograft. The American Journal of Sports Medicine. 2012. DOI: 10.1177/0363546512449815

[18] Serial magnetic resonance imaging of the donor site after harvesting the central third of the patellar tendon. Knee Surgery, Sports Traumatology, Arthroscopy. 1999. DOI: 10.1007/s001670050115

[19] Calcification of the patellar tendon after ACL reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2004. DOI: 10.1007/s00167-003-0424-1

[20] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Operative Treatment of Extensor Mechanism Injuries.

[21] Neglected Ruptures of the Patellar Tendon. The American Journal of Sports Medicine. 2001. DOI: 10.1177/03635465010290041301

[22] Poorer functional Outcomes in Patients with Multi‐Ligamentous Knee Injury with Concomitant Patellar Tendon Ruptures at 5 years Follow‐Up. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07110-3

[23] Aaos Comprehensive Orthopaedic Review 3. Extensor Mechanism Injuries > IV Patellar or Quadriceps Tendinopathy.

[25] Combined repair technique for patellar tendon rupture using two suture anchors and three transosseous sutures: a retrospective cohort study. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-09018-8

[26] Allograft reconstruction of the patellar ligament. A case report.. The Journal of Bone & Joint Surgery. 1994. DOI: 10.2106/00004623-199407000-00019

[27] Ipsilateral Hamstring Tendon Graft Reconstruction for Chronic Patellar Tendon Ruptures. Journal of Bone and Joint Surgery. 2013. DOI: 10.2106/jbjs.l.01462

[29] Aaos Comprehensive Orthopaedic Review 3. Extensor Mechanism Injuries > III Rupture of the Patellar Tendon or Quadriceps Tendon.

[30] Acute traumatic rupture of the patellar tendon in pediatric population: Case series and review of the literature. Injury. 2017. DOI: 10.1016/j.injury.2017.08.069

[31] Complications involving the extensor mechanism after total knee arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3189-9

[32] Reconstruction of chronic patellar tendon rupture with contralateral bone-tendon-bone autograft. Knee Surgery, Sports Traumatology, Arthroscopy. 2015. DOI: 10.1007/s00167-015-3951-7

[36] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Extensor Mechanism Injuries.

[40] Arthroscopic suture repair of acute quadriceps tendon ruptures. Orthopaedics & Traumatology: Surgery & Research. 2017. DOI: 10.1016/j.otsr.2016.12.018

[44] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Chronic or Neglected Quadriceps and Patellar Tendon Ruptures > Acute Patellar Tendon Repair.

[46] Reconstruction of a chronic quadriceps tendon tear in a body builder. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0044-7

[47] Rethinking Patellar Tendinopathy and Partial Patellar Tendon Tears: A Novel Classification System. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546519894333

[48] Infections and Patellar Tendon Ruptures After Anterior Cruciate Ligament Reconstruction. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546510388163

[53] Acute Patellar Tendon Ruptures: An Update on Management. JAAOS: Global Research and Reviews. 2024. DOI: 10.5435/jaaosglobal-d-24-00060

[54] Extensor mechanism ruptures. EFORT Open Reviews. 2022. DOI: 10.1530/eor-22-0021

[55] Aaos Comprehensive Orthopaedic Review 3. Extensor Mechanism Injuries > Patellar or Quadriceps Tendinopathy.

[57] Patellar Tendon Ruptures in National Football League Players. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546511417083

[59] Reconstruction of a chronic patellar tendon rupture with semitendinosus autograft. Archives of Orthopaedic and Trauma Surgery. 2014. DOI: 10.1007/s00402-014-2080-y

[61] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Soft-­Tissue Injuries About the Knee > Patellar Tendon > Patellar Tendon Rupture.

[64] Suture Anchor Repair of Quadriceps Tendon Rupture After Total Knee Arthroplasty. The Journal of Arthroplasty. 2011. DOI: 10.1016/j.arth.2011.01.006

[65] Two‐Dimensional Magnetic Resonance Imaging in Preparation for Autograft Anterior Cruciate Ligament Reconstruction Demonstrates Quadriceps Tendon Is Thicker Than Patellar Tendon. Arthroscopy, Sports Medicine, and Rehabilitation. 2023. DOI: 10.1016/j.asmr.2023.04.005

[66] Chronic patellar tendon rupture reconstruction with a semitendinosus autograft. Orthopaedics & Traumatology: Surgery & Research. 2011. DOI: 10.1016/j.otsr.2011.01.015

[69] Arthroscopic patellar release for treatment of chronic symptomatic patellar tendinopathy: long-term outcome and influential factors in an athletic population. BMC Musculoskeletal Disorders. 2017. DOI: 10.1186/s12891-017-1851-3

[96] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Pathoanatomy and Applied Anatomy Related to Extensor Mechanism Injuries.

[102] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Acute Patellar Tendon Rupture.

[110] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Soft Tissue Anatomy.

[114] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Nonoperative Treatment of Extensor Mechanism Rupture.

[127] Bilateral patellar tendon rupture on lupus undergoing corticosteroids: a case report. BMC Musculoskeletal Disorders. 2020. DOI: 10.1186/s12891-020-03513-w

[129] Demonstration of avulsion fracture of the inferior pole of the patella by magnetic resonance imaging. A case report.. The Journal of Bone & Joint Surgery. 1995. DOI: 10.2106/00004623-199511000-00012

[133] Evaluation of harvested and normal patellar tendons: a reliability analyses of magnetic resonance imaging and ultrasonography. Knee Surgery, Sports Traumatology, Arthroscopy. 2000. DOI: 10.1007/s001670000132

[147] Athletes With Partial Extensor Mechanism Tears of the Knee Achieve Variable Return‐to‐Sport Rates Following Operative Versus Nonoperative Management: A Systematic Review. Arthroscopy, Sports Medicine, and Rehabilitation. 2024. DOI: 10.1016/j.asmr.2024.100944

[157] Management of Patellar Tendinopathy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2023.09.004

[159] Patients with a quadriceps tendon shorter than 60 mm require a patellar bone plug autograft in anterior cruciate ligament reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06261-5

[164] A Comprehensive Return-to-Play Analysis of National Basketball Association Players With Operative Patellar Tendon Tears. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118800479

Creative Commons BY-NC 4.0

CC Creative Commons licence
BY Attribution — you must credit the source
NC NonCommercial — not for commercial use

Attribution-NonCommercial 4.0 International

Creative Commons Corporation ("Creative Commons") is not a law firm and does not provide legal services or legal advice. Distribution of Creative Commons public licenses does not create a lawyer-client or other relationship. Creative Commons makes its licenses and related information available on an "as-is" basis. Creative Commons gives no warranties regarding its licenses, any material licensed under their terms and conditions, or any related information. Creative Commons disclaims all liability for damages resulting from their use to the fullest extent possible.

Using Creative Commons Public Licenses

Creative Commons public licenses provide a standard set of terms and conditions that creators and other rights holders may use to share original works of authorship and other material subject to copyright and certain other rights specified in the public license below. The following considerations are for informational purposes only, are not exhaustive, and do not form part of our licenses.

Considerations for licensors: Our public licenses are intended for use by those authorized to give the public permission to use material in ways otherwise restricted by copyright and certain other rights. Our licenses are irrevocable. Licensors should read and understand the terms and conditions of the license they choose before applying it. Licensors should also secure all rights necessary before applying our licenses so that the public can reuse the material as expected. Licensors should clearly mark any material not subject to the license. This includes other CC- licensed material, or material used under an exception or limitation to copyright. More considerations for licensors: wiki.creativecommons.org/Considerations_for_licensors

Considerations for the public: By using one of our public licenses, a licensor grants the public permission to use the licensed material under specified terms and conditions. If the licensor's permission is not necessary for any reason--for example, because of any applicable exception or limitation to copyright--then that use is not regulated by the license. Our licenses grant only permissions under copyright and certain other rights that a licensor has authority to grant. Use of the licensed material may still be restricted for other reasons, including because others have copyright or other rights in the material. A licensor may make special requests, such as asking that all changes be marked or described. Although not required by our licenses, you are encouraged to respect those requests where reasonable. More considerations for the public: wiki.creativecommons.org/Considerations_for_licensees

Creative Commons Attribution-NonCommercial 4.0 International Public License

By exercising the Licensed Rights (defined below), You accept and agree to be bound by the terms and conditions of this Creative Commons Attribution-NonCommercial 4.0 International Public License ("Public License"). To the extent this Public License may be interpreted as a contract, You are granted the Licensed Rights in consideration of Your acceptance of these terms and conditions, and the Licensor grants You such rights in consideration of benefits the Licensor receives from making the Licensed Material available under these terms and conditions.

Section 1 -- Definitions.

a. Adapted Material means material subject to Copyright and Similar Rights that is derived from or based upon the Licensed Material and in which the Licensed Material is translated, altered, arranged, transformed, or otherwise modified in a manner requiring permission under the Copyright and Similar Rights held by the Licensor. For purposes of this Public License, where the Licensed Material is a musical work, performance, or sound recording, Adapted Material is always produced where the Licensed Material is synched in timed relation with a moving image.

b. Adapter's License means the license You apply to Your Copyright and Similar Rights in Your contributions to Adapted Material in accordance with the terms and conditions of this Public License.

c. Copyright and Similar Rights means copyright and/or similar rights closely related to copyright including, without limitation, performance, broadcast, sound recording, and Sui Generis Database Rights, without regard to how the rights are labeled or categorized. For purposes of this Public License, the rights specified in Section 2(b)(1)-(2) are not Copyright and Similar Rights.

d. Effective Technological Measures means those measures that, in the absence of proper authority, may not be circumvented under laws fulfilling obligations under Article 11 of the WIPO Copyright Treaty adopted on December 20, 1996, and/or similar international agreements.

e. Exceptions and Limitations means fair use, fair dealing, and/or any other exception or limitation to Copyright and Similar Rights that applies to Your use of the Licensed Material.

f. Licensed Material means the artistic or literary work, database, or other material to which the Licensor applied this Public License.

g. Licensed Rights means the rights granted to You subject to the terms and conditions of this Public License, which are limited to all Copyright and Similar Rights that apply to Your use of the Licensed Material and that the Licensor has authority to license.

h. Licensor means the individual(s) or entity(ies) granting rights under this Public License.

i. NonCommercial means not primarily intended for or directed towards commercial advantage or monetary compensation. For purposes of this Public License, the exchange of the Licensed Material for other material subject to Copyright and Similar Rights by digital file-sharing or similar means is NonCommercial provided there is no payment of monetary compensation in connection with the exchange.

j. Share means to provide material to the public by any means or process that requires permission under the Licensed Rights, such as reproduction, public display, public performance, distribution, dissemination, communication, or importation, and to make material available to the public including in ways that members of the public may access the material from a place and at a time individually chosen by them.

k. Sui Generis Database Rights means rights other than copyright resulting from Directive 96/9/EC of the European Parliament and of the Council of 11 March 1996 on the legal protection of databases, as amended and/or succeeded, as well as other essentially equivalent rights anywhere in the world.

l. You means the individual or entity exercising the Licensed Rights under this Public License. Your has a corresponding meaning.

Section 2 -- Scope.

a. License grant.

1. Subject to the terms and conditions of this Public License, the Licensor hereby grants You a worldwide, royalty-free, non-sublicensable, non-exclusive, irrevocable license to exercise the Licensed Rights in the Licensed Material to:

a. reproduce and Share the Licensed Material, in whole or in part, for NonCommercial purposes only; and

b. produce, reproduce, and Share Adapted Material for NonCommercial purposes only.

2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.

3. Term. The term of this Public License is specified in Section 6(a).

4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a) (4) never produces Adapted Material.

5. Downstream recipients.

a. Offer from the Licensor -- Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.

b. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).

b. Other rights.

1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.

2. Patent and trademark rights are not licensed under this Public License.

3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties, including when the Licensed Material is used other than for NonCommercial purposes.

Section 3 -- License Conditions.

Your exercise of the Licensed Rights is expressly made subject to the following conditions.

a. Attribution.

1. If You Share the Licensed Material (including in modified form), You must:

a. retain the following if it is supplied by the Licensor with the Licensed Material:

i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);

ii. a copyright notice;

iii. a notice that refers to this Public License;

iv. a notice that refers to the disclaimer of warranties;

v. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;

b. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and

c. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.

2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.

3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.

4. If You Share Adapted Material You produce, the Adapter's License You apply must not prevent recipients of the Adapted Material from complying with this Public License.

Section 4 -- Sui Generis Database Rights.

Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

a. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database for NonCommercial purposes only;

b. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material; and

c. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

Creative Commons is not a party to its public licenses. Notwithstanding, Creative Commons may elect to apply one of its public licenses to material it publishes and in those instances will be considered the “Licensor.” The text of the Creative Commons public licenses is dedicated to the public domain under the CC0 Public Domain Dedication. Except for the limited purpose of indicating that material is shared under a Creative Commons public license or as otherwise permitted by the Creative Commons policies published at creativecommons.org/policies, Creative Commons does not authorize the use of the trademark "Creative Commons" or any other trademark or logo of Creative Commons without its prior written consent including, without limitation, in connection with any unauthorized modifications to any of its public licenses or any other arrangements, understandings, or agreements concerning use of licensed material. For the avoidance of doubt, this paragraph does not form part of the public licenses.

Creative Commons may be contacted at creativecommons.org.