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Patella fracture

77 citationsUpdated Sep 2026

Overview

Patellar fractures are an increasing concern in female and elderly populations [3], with a rare incidence of approximately 0.44% in children [12]. These injuries are associated with a lifelong increased risk of total knee arthroplasty [2]. In the pediatric population, patellar sleeve fractures are the most common type, typically occurring between 8 and 12 years of age [12]. Understanding the etiologic factors leading to atraumatic patellar fractures is essential for minimizing complications [1]. Clinically, a history of trauma, knee effusion, inability to actively extend the knee, high-riding patella, or a palpable gap raises suspicion for fracture [12]. These findings must be differentiated from bipartite patella, a normal variant present in ≤5% of knees characterized by rounded borders and superolateral location [12].

Diagnosis relies on identifying specific fracture patterns, including transverse, stellate, vertical, apical, and osteochondral types [16]. Displaced fractures are defined by fragment separation of more than 3 mm or articular incongruity of more than 2 mm [16]. Vertical fracture patterns are easily missed on AP radiographs, emphasizing the importance of axial views [16]. For patellar sleeve fractures, plain radiographs may show only patella alta or baja, necessitating ultrasonography or MRI to assess cartilaginous injury and fragment displacement when radiographs are inconclusive [12].

Treatment has evolved from nonoperative management to operative fixation aimed at restoring extensor mechanism integrity and articular congruity [9]. Displaced fractures with extensor mechanism disruption generally require operative treatment to maximize long-term outcomes [8]. Nonsurgical treatment is indicated for nondisplaced or minimally displaced fractures in children without an extensor lag [12]. Surgical fixation is required for fractures displaced greater than 2 mm at the articular surface, confirmed by an extensor lag or inability to actively extend the knee [12]. Patellar sleeve fractures require surgery [12]. While surgical management remains crucial, fracture fixation using plating systems or small fragment screws is least associated with postoperative complications [7].

Anatomy & Pathophysiology

Bony Anatomy & Biomechanics

The patella is the largest human sesamoid bone and functions as a key component of the knee extensor mechanism [65]. It operates alongside the quadriceps tendon, the patellar ligament, and the extensor retinaculum [65]. Biomechanically, the patella transmits tensile forces from the quadriceps muscle to the patellar ligament [65]. By displacing the extensor mechanism anterior to the axis of knee rotation, the patella increases the moment arm of the mechanism [65]. An intact patella increases the leverage and efficiency of the extensor mechanism [49] and maintains the lever arm for quadriceps function [73]. The bone articulates with the femoral trochlea [49]. Because the patella is a relatively subcutaneous bone, it is subject to injury from a direct blow [65]. This anterior subcutaneous location renders it vulnerable to direct trauma [27]. During knee flexion, the patella is loaded in tension with quadriceps contraction and is subject to three-point bending [65]. The most significant effect of a patellar fracture is the loss of continuity of the extensor mechanism of the knee [27]. Integrity of the extensor mechanism is necessary for active knee extension and normal gait [68].

Mechanisms of Injury

Patellar fractures may result from either direct or indirect forces but usually involve a combination of the two [30]. These fractures account for approximately 1% of all skeletal fractures [38]. The incidence of patellar fractures rises steadily with age as bone quality declines [38]. Fractures in children are rare, with an incidence of around 0.44% [12].

Direct Injury: Direct injuries may be low energy, such as after a fall from a sitting or standing height, or high energy, as from a dashboard impact in a motor vehicle collision [38]. A direct blow to the patella typically results in a comminuted or stellate fracture pattern with articular injury [30]. Comminuted fracture patterns are often the result of high-energy, direct injuries [38]. Vertical fractures are typically the result of a direct blow to a partially flexed knee [38]. Comminuted, stellate fracture patterns are typically the result of a direct blow with impaction against the femoral condyles [38] and can be associated with substantial injury to both the femoral and patellar chondral surfaces [38].

Indirect Injury: Indirect injuries occur secondary to the large forces generated through the extensor mechanism, typically from forceful contraction of the quadriceps with the knee in a flexed position [38]. Indirect trauma typically occurs when the mechanical properties of bone are overcome by eccentric loading forces [30]. The patella fails under tension by rapid knee flexion against a contracted quadriceps during indirect injury [30]. Fractures caused by indirect mechanisms are usually transverse and may be associated with tears of the medial and lateral retinacular expansions [27]. Fractures resulting from tension failure are often simple and transverse in nature, with chondral surfaces that may be relatively uninjured [65]. Indirect injuries frequently cause a greater degree of retinacular disruption compared with direct injuries [38]. Active knee extension is compromised in most cases of indirect injury [38]. Most patella fractures have a transverse fracture pattern resulting from excessive tensile forces through the extensor mechanism [38]. The degree of fragment displacement is generally representative of occult injury to the adjacent soft tissue envelope [38].

Fracture Patterns & Classification

The vertical fracture line is most commonly seen involving the lateral facet and lying between the middle and lateral third of the patella [16]. Fractures at the proximal pole of the patella are typically bony avulsions of the quadriceps mechanism [16]. Distal pole fractures are bony avulsions of the patellar tendon [16]. Displacement occurs in up to 11.5% of distal pole fractures in large series [16]. A lateral radiograph will demonstrate patella alta and an increased Insall–Salvati ratio in distal pole fractures [16]. Conversely, a lateral radiograph may demonstrate patella baja and a reduced Insall–Salvati ratio in proximal pole fractures [16].

Recent studies show that only 16% of all patellar fractures are isolated transverse fractures, whereas most have multiple fracture lines [83]. A dominant transverse fracture line is present in 92.8% of all patellar fractures [83]. Comminution of the inferior pole was seen in 36 (88%) of 41 CT scans of fractures, but radiographs identified this comminution in only 16 (44%) [83].

Patellar Sleeve Fractures: Patellar sleeve fractures occur when a chondral sleeve of the patella separates from the main portion of the patella and ossific nucleus [12]. These injuries should be considered when the examination is concerning for patellar tendon rupture [12]. In a sleeve fracture, a large cartilaginous fragment usually is attached to a fleck of bone [109]. If a sleeve fracture heals in an elongated position, it may contribute to chronic recurrent dislocation [109].

Pediatric & Developmental Anatomy

Bipartite patella has rounded borders [12] and is located superolaterally [12]. A history of trauma, knee effusion, inability to actively extend the knee, high riding patella, and sometimes a palpable gap help raise suspicion of a patellar fracture in children [12]. Fractures of the distal pole of the patella and transverse fractures occur often in children with cerebral palsy and spasticity of the quadriceps muscle [109]. In adolescents, “jumper’s knee” and Sinding-Larsen-Johansson syndrome occur frequently as avulsion injuries of the proximal and distal poles of the patella [109]. Congenital absence of the patella or congenital hypoplasia may be seen in onychoosteodysplasia or nail-patella syndrome [109].

Pathophysiology & Complications

Patellar fractures can lead to stiffness, extension weakness, and patellofemoral arthritis [49]. The consequences of a patellar fracture may be more severe than previously considered, with a lifelong increased risk of knee arthroplasty [2]. The presence of an isolated medial fragment serves as an indicator of increased risk for postoperative lateral patellar displacement [11]. Patella baja is associated with poor functional outcomes after patella fracture fixation [70]. A fuller understanding of the pathophysiology of late patella baja would be helpful in both the prevention and treatment of the condition [37].

Mildly displaced fractures of the patella treated in a plaster cylinder may lead to disuse osteoporosis of the patella and a subsequent refracture [84]. Osteoporosis has been found to be one of the factors responsible for refracture of the patella at the original site of injury when the fracture had healed by fibrous union [84]. Osteoporosis secondary to splinting may be responsible for a refracture at a different site in the patella [84]. The prognosis of complex knee injuries with a combination of ligamentous injuries and associated fractures is much worse compared to either injury alone [50].

Classification

General Principles: Patellar fracture classification is typically descriptive, based on fracture pattern, degree of displacement, or mechanism of injury [16]. The current OTA classification is important for standardizing the classification of patellar fractures for clinical research [16]. Prior to the OTA classification, patellar fracture classification lacked standardization, and most clinical series reported outcomes based on the type of fixation rather than fracture pattern [16]. A useful approach in the clinical setting begins with classifying patellar fractures as displaced or nondisplaced [16]. After this initial categorization, injuries can be further categorized on the basis of the geometric configuration and location of fracture lines [16]. The location of the fracture, whether in the middle or at the poles, can affect treatment [16]. CT imaging enhances the classification and mapping of patellar fractures [43]. CT imaging highlights the central patella as the primary site of injury [43].

Nondisplaced Fractures: Nondisplaced transverse fractures are typically associated with indirect, longitudinal forces that fracture the patella but are insufficient to tear the medial and lateral patellar retinacula [16]. In these injuries, the extensor mechanism remains competent [16]. The preserved integrity of the soft tissue envelope helps to maintain the reduction in nondisplaced transverse fractures [16]. Stellate fractures typically result from direct blow injuries to the patella with the knee in a partially flexed position [16]. Active knee extension is preserved in nondisplaced stellate fractures as the medial and lateral patellar retinacula are usually not torn [16]. Damage to the patellar and femoral articular surface is not uncommon in nondisplaced stellate fractures [16]. Careful evaluation on tangential views or MRI is necessary to identify occult osteochondral lesions in nondisplaced stellate fractures [16]. A vertical or longitudinal fracture pattern accounts for 12% to 22% of patellar fractures in several large series [16]. Lateral avulsion was reported as the most common mechanism for vertical fractures in 75% of a specific series [16]. Direct compression of the patella in a hyperflexed knee has been reported as a mechanism for vertical fractures [16]. The patellar retinacula are intact in vertical fractures, preserving active knee extension [16]. The vertical fracture pattern is easily missed on an AP radiograph, emphasizing the importance of an axial view [16].

Displaced Fractures: Evaluation of the integrity of the extensor mechanism is critical with displaced transverse fractures [16]. Fracture fragment separation greater than 3 mm is suggestive but not diagnostic of retinacular and extensor mechanism disruption in displaced transverse fractures [16]. A subset of displaced transverse fractures exists with intact retinacula, characterized by preservation of full active knee extension [16]. Displaced, stellate fractures usually result from a high-energy, direct blow to the patella [16]. Displaced stellate fractures typically demonstrate a high degree of comminution [16]. Anterior soft tissue contusion and/or lacerations are not uncommon in displaced stellate fractures [16]. Transverse fracture lines with extensive comminution may result in propagation into the retinaculum and disruption of the extensor mechanism [16]. Significant articular incongruity in displaced stellate fractures may warrant operative intervention even if the extensor mechanism is preserved [16]. Active knee extension may be preserved in proximal pole fractures if the medial and lateral retinacula remain intact [16].

Pediatric and Special Populations: Patellar fractures in children are categorized based on location, fracture configuration, and amount of displacement [12]. Patellar fractures in children need to be differentiated from bipartite patella, which is a normal variant present in ≤5% of knees [12]. Bipartite patella has rounded borders, differing from a patellar fracture [12]. Bipartite patella is located superolaterally, differing from a patellar fracture [12]. Transverse fracture of the patella is a rarity in children under 15 years [31].

Mechanism-Based Classification: Patellar fractures may result from either direct or indirect forces but usually involve a combination of the two forces [30]. A direct blow to the patella usually results from a ground level fall or dashboard injury from a motor vehicle collision [30]. The direct blow mechanism of injury typically results in a comminuted/stellate fracture pattern with articular injury [30]. The patella fails under tension by rapid knee flexion against a contracted quadriceps in indirect injuries [30]. Indirect injuries present as a transverse fracture pattern with larger displacement, retinacular injury, and less articular injury/impaction [30]. Open patellar fractures are high energy injuries associated with significantly higher rates of associated injuries compared to closed fractures [36].

Clinical Presentation

Epidemiology and Demographics

Patellar fractures constitute approximately 1% of all skeletal injuries [27] [38] [65]. In the pediatric population, these injuries are rare, with an incidence of around 0.44% [12]. While patellar tendon ruptures occur more commonly in patients less than 40 years old [19], quadriceps tendon ruptures are more frequent in patients greater than 40 years of age [19]. In elderly patients above 65 years, patella fractures were not associated with an increased mortality rate, with a relative risk of death of 0.9 [51].

Mechanisms of Injury

The anterior subcutaneous location of the patella renders it vulnerable to direct trauma, such as the knee striking a motor vehicle dashboard or a fall on the anterior knee [27]. Indirect mechanisms result from violent contraction of the quadriceps with the knee flexed [27]. Most patellar fractures are caused by a combination of direct and indirect forces [27]. A low-energy mechanism, such as a ground-level fall with eccentric loading of the quadriceps, should raise suspicion for a patella fracture or rupture of the quadriceps or patellar tendons [137]. Conversely, a higher energy mechanism, such as a direct blow from a dashboard, should alert the surgeon to a possible extensor mechanism injury and other associated ipsilateral injuries [137]. Associated ipsilateral injuries in high-energy mechanisms include proximal tibia fractures, knee ligamentous injuries, distal, midshaft, and proximal femur fractures, acetabular fractures, and/or hip dislocations [137]. In high-energy direct injuries, it is critical to survey for associated injuries of the ipsilateral limb, including hip dislocation, proximal femur fractures, or fractures and ligamentous injuries about the knee [38]. Although PCL injuries requiring surgery are rare, 25% of patients requiring surgery for patellar fractures presented with a PCL injury [47].

Physical Examination

Patellar fractures generally present with hemarthrosis and localized tenderness [27]. Localized pain, swelling, contusion, and abrasions are common physical findings after patellar injury [111]. Complaints of anterior knee pain, swelling, and difficulty ambulating after a fall are common and may reflect an injury to the extensor mechanism [122]. In fractures that are displaced or have concomitant retinacular tears, a palpable defect may be present [27]. Displaced patella fractures typically present with an acute hemarthrosis and a tender, palpable defect between the fracture fragments [122]. The absence of a large effusion in the presence of a palpable bony defect should raise concern for associated retinacular tears [122]. Lacerations or abrasions to the skin overlying the patella may reflect an occult open fracture or communication with the knee joint [122].

In children, a history of trauma, knee effusion, inability to actively extend the knee, high riding patella, and sometimes a palpable gap would help raise suspicion of a patellar fracture [12]. Patellar sleeve fractures should be considered when the examination is concerning for patellar tendon rupture in children [12].

Extensor Mechanism Assessment

Competence of the extensor mechanism must be assessed by asking the patient to perform a straight-leg raise or extend a partially flexed knee against gravity [122]. Inability of the patient to extend the affected knee actively usually indicates a disruption of the extensor mechanism or a torn retinaculum [27]. The patient's ability to extend the knee does not rule out a patella fracture but suggests that the continuity of the extensor mechanism is maintained via an intact retinacular sleeve [122]. A large hemarthrosis may be very painful and limit the ability of the patient to comply with the extensor mechanism examination [122]. Aspiration of the hemarthrosis followed by injection of a local anesthetic into the joint may be helpful if pain limits examination [122].

Patients with a loss of active knee extension as a result of trauma without signs of a patellar fracture may have a disruption of the extensor mechanism [121]. Injuries to the extensor mechanism can include quadriceps or patellar tendon ruptures, patellar dislocations, or tibial tubercle avulsions [121]. Quadriceps and patellar tendon ruptures are typically low-energy injuries [121]. 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 [121]. Patellar tendon ruptures extend completely through the retinacular tissue resulting in complete loss of knee extension [121]. Quadriceps tendon ruptures may not involve as much of the retinacular tissue, and some extension may still be possible [121]. Some degree of extensor lag is almost always present when compared with the uninjured limb in quadriceps tendon ruptures [121]. A defect may be palpable at the level of the rupture immediately after injury [121]. When the diagnosis is delayed, the tendon defect may not be palpable secondary to consolidation of the hematoma and early scar formation [121]. A traumatic hemarthrosis is common after extensor mechanism injuries [121].

Imaging and Diagnostic Studies

Plain radiography is typically sufficient to confirm the diagnosis of patellar fracture or injury to the extensor mechanism [64]. Anteroposterior (AP), lateral, and tangential or axial views of the patellofemoral joint should be obtained for patellar fractures [64]. The AP view should be taken with the largest cassette possible (typically 14 × 17 in) placed behind the knee of the supine patient [64]. The degree of fracture comminution is typically underestimated by the radiographically evident fracture lines [64]. The distal femur and proximal tibia must be carefully inspected for occult condylar or plateau fractures [64]. A bipartite or tripartite patella can often be mistaken for a fracture in the setting of a trauma history [64]. Bipartite patella opposing edges are usually smooth and corticated on plain radiographs [64]. The most common bipartite pattern is located in the superolateral aspect of the patella [64].

The lateral radiographic view is critical to define fracture pattern and associated extensor mechanism disruption [64]. Patellar height should be assessed using the Insall–Salvati ratio, which compares the height of the patella to the length of the patellar tendon [64]. A normal Insall–Salvati ratio is 1.02 ± 0.13 [64]. An Insall–Salvati ratio of less than 1 suggests patella alta and disruption of the patellar tendon [64]. An Insall–Salvati ratio of greater than 1 is associated with patella baja and quadriceps tendon disruption [64]. With the knee flexed 90 degrees, the proximal patellar pole normally rests at or below the level of the anterior cortex of the femur [64]. With the knee flexed 30 degrees, the inferior patellar pole normally projects to the level of Blumensaat's line [64]. Loss of the relationship between the inferior patellar pole and Blumensaat's line is suggestive of extensor mechanism disruption [64]. A tangential or axial view of the patellofemoral joint is useful for visualizing vertical or marginal fracture lines and associated osteochondral defects [64].

CT imaging enhances the classification and mapping of patellar fractures, highlighting the central patella as the primary site of injury [43]. 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 [44]. Ultrasonography is helpful when plain radiographs are not conclusive for patellar sleeve fractures in children [12].

The saline load test can be used to determine if an open wound communicates with the joint [27]. The saline load test may not be 100% reliable in open fractures with very small traumatic arthrotomies [27]. A 2013 study revealed a sensitivity of 94% and a specificity of 91% for the saline load test in detecting atraumatic arthrotomy [137]. The addition of methylene blue to the saline load test was not shown to improve its sensitivity [137]. Bone scanning may be indicated for detection of occult stress fractures in young athletes and patients with cerebral palsy [111].

Pediatric Specifics

Patellar sleeve fractures are often missed on initial presentation [12]. Sleeve fractures of the patella can occur at the superior pole but are typically located at the inferior pole [40]. The extensor mechanism may be disrupted at the inferior pole of the patella where the patellar tendon originates, usually in a child aged between 8 and 12 years [19]. In pediatric sleeve fractures, the distal pole of the patella plus a large sleeve of articular cartilage is pulled off [19]. A small osseous portion of a displaced pediatric sleeve fracture fragment is visible on radiographs, but the cartilaginous portion is not seen [19].

Extensor Mechanism Injuries

ACL tears have accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture [121]. Patellar tendon ruptures occur more frequently in patients less than 40 years old [19]. The patient cannot actively extend the knee, the patella is high-riding, and a defect is palpable beneath the patella in patellar tendon rupture [19]. Chronic patellar tendon ruptures are very hard to treat [19]. The quadriceps must be freed up from the femur and the patella pulled down to the proper location for chronic patellar tendon ruptures [19]. The gracilis and semitendinosus tendons can be used to substitute for the patellar tendon in chronic ruptures [19].

Radiographs of the knee after patellar tendon rupture demonstrate patella alta, particularly with the knee flexed [134]. Radiographs obtained after quadriceps tendon rupture demonstrate patella baja and sometimes show bony fragments in the region of the rupture [134]. MRI can be helpful when the diagnosis is uncertain, particularly when differentiating between a partial and a complete rupture of a tendon [134]. Patients with a complete rupture of either tendon cannot extend the knee against resistance or perform a straight leg raise [134]. In incomplete ruptures or in patients with a complete rupture of the quadriceps tendon but an intact retinaculum, the ability to perform a straight leg raise against gravity may be uncompromised [134].

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 [134]. Anabolic steroid use and local corticosteroid injection into the tendon are associated with both patellar and quadriceps tendon ruptures [134]. Both patellar tendon and quadriceps tendon ruptures typically occur at the tendon attachment to the patella [134]. Underlying chronic degeneration often is present in tendon ruptures, characterized by angiofibroblastic tendinosis, mucoid degeneration, and pseudocyst formation at the attachment of tendon to bone [134]. The quadriceps tendon has been described as having two to four distinct layers [134]. Patellar tendon rupture has been reported after midthird tendon harvest for knee ligament reconstruction [134].

The rupture typically occurs during an eccentric load on a flexed knee, such as landing from a jump or taking a forceful step while descending stairs [134]. A rupture can occur during a forceful quadriceps contraction when taking off for a jump [134]. Patients with a rupture of the patellar tendon or quadriceps tendon often report a history of pain, consistent with the presence of underlying tendon degeneration [134]. Physical examination for a complete rupture of either tendon demonstrates tenderness at the site of the injury, hematoma, and a palpable defect in the tendon [134].

Investigations

Plain radiography: Lateral radiographs identify a dominant transverse fracture line in 92.8% of all patellar fractures [83]. However, visualization of all fracture lines in multifragmentary patterns can be difficult on radiographs [83]. In patellar sleeve fractures, the only sign on plain radiographs may be patella alta [12]. Conversely, patella baja may be the only finding for proximal patellar sleeve fractures [12].

CT: Computed tomography analysis reveals that only 16% of patellar fractures are simple transverse type-C1 fractures [83]. CT is superior to radiography for detecting comminution; it identified inferior pole comminution in 88% of 41 CT scans, whereas radiographs identified this comminution in only 44% of cases [83]. In the elderly, patellar fractures are mostly from low-energy injuries, with CT images demonstrating high rates of inferior pole involvement and comminution [160].

MRI: MRI can show the extent of cartilaginous injury and displacement of fracture fragments in patellar sleeve fractures [12].

Other Considerations: Native patellar thickness was inversely correlated with periprosthetic patellar fracture risk after total knee arthroplasty [87]. Lateral positioning during resurfacing and increased component size were associated with increased risk of periprosthetic patellar fracture after total knee arthroplasty [87].

Treatment

Non-Operative

Nonoperative management is indicated for patellar fractures with less than 3 mm of articular incongruity and an intact extensor mechanism [71], including nondisplaced fractures [49]. In children, nonsurgical management is appropriate for nondisplaced and minimally displaced fractures without an extensor lag [12]. Acute nonoperative treatment typically consists of 4 to 6 weeks of extension splinting or bracing [71]. Long-leg cylinder casting may be preferable to bracing if patient compliance and reliability are a concern [71]. Straight-leg raises and isometric quadriceps exercises are initiated early in the cast or brace to minimize atrophy [71]. Range of motion is gradually initiated after there is evidence of fracture consolidation on plain radiographs [71]. Most modern protocols allow for some degree of early weight bearing in full extension [71].

Nonsurgical management can be considered in patients with substantial medical comorbidities that might preclude surgery or in patients who are minimal ambulators or nonambulators [119]. Nonoperative management is also appropriate in most patients with periprosthetic patella fractures, even when the extensor mechanism is not intact [113]. In a series of 422 patellar fractures, 98% of minimally displaced fractures treated nonoperatively had good to excellent results at final follow-up [71]. There was no relationship between articular incongruity of <3 mm and the development of posttraumatic arthritis over an average follow-up of 8.9 years in this series [71]. Other series have reported low failure rates of less than 5% with closed management of minimally displaced fractures [71].

Operative

Indications: Surgical fixation is recommended for fractures that either disrupt the extensor mechanism or demonstrate >2 to 3 mm step-off and >1 to 4 mm of displacement [49]. Relative surgical indications for displaced patella fractures include disruption of the extensor mechanism, substantial fracture displacement or articular incongruity, the presence of an open fracture, or free-floating intra-articular osteochondral fragments [119]. In children, patellar fractures displaced greater than 2 mm at the articular surface should be fixed surgically [12]. Surgical management of periprosthetic patella fractures is usually reserved for disturbance of the extensor mechanism integrity, a loose patellar component, and patellar maltracking [113]. Surgical treatment should be mandatory in case of displacement (>4 mm) and comminuted fracture with a torn extensor retinaculum [75].

Surgical Approach / Technique: Currently, three forms of operative treatment for displaced patella fractures are most commonly used: open reduction and internal fixation, partial patellectomy with soft tissue repair, and total patellectomy [45]. The goals of surgical treatment are the restoration of the functional integrity and strength of the extensor mechanism, maximizing articular congruity, and preservation of patellar bone [45]. Anatomic reduction and fixation with a tension-band technique is associated with the best outcomes for patellar fractures [49]. For osseous fractures in children, fixation is performed with tension banding, and a cerclage wire may be needed for extensively comminuted fractures [12]. With displaced patellar sleeve fractures in children, open reduction and internal fixation with tension band wiring are recommended [19].

Fracture fixation using plating systems or small fragment screws is least associated with postoperative complications in surgical management of patellar fractures [7]. A modified tension band technique is found to be a useful technique for the treatment of comminuted and simple fractures of the patella [23]. The biomechanical properties of the fixed-angle plate seem promising and convincing in providing a rigid and stable fixation method for transverse patella fractures [52]. Total patellectomy technique was a safe and reliable alternative treatment for treating patients with highly comminuted patella fractures when anatomically reduction and rigid fixation were difficult [17]. The turned-over patella operation method exhibited some superiority to conventional reduction-fixation approach for treatment of C3-type patellar fractures in terms of efficacy and safety by enlarging the ROM of the knee joint and promoting functional recovery [114]. The loop anchor tension band technique is safe and effective for treating patella fractures [126]. A new tension band fixation technique using braided polyblend sutures resulted in good outcomes and is considered clinically effective for patellar fracture reduction [123]. Rim-plate-augmented separate vertical wiring may be an effective fixation method for treating displaced, comminuted inferior pole fracture of the patella [128]. The method of open reduction and external compressive skeletal fixation preserves the patella intact when principal fragments are present, though partial patellectomy may be required for comminuted fractures with unreducible small fragments [24].

Implant Selection: When there is adequate bone stock (more than 10 mm), revision of the patellar component is reasonable for periprosthetic patella fractures [113]. Avulsion fractures of the proximal or distal pole of the patella are amenable to suture repair [113]. Severe bone deficiency in periprosthetic patella fractures usually mandates patellar resection arthroplasty with partial or complete patellectomy [113]. A novel reconstructive technique for type IIIB periprosthetic patella fractures uses multiple Steinmann pins to reduce and stabilize the patella as a scaffold for bone grafting, with a patellar button cemented into the construct [113].

Outcomes and Complications: Symptomatic hardware is a frequent complication of anatomic reduction and fixation with a tension-band technique [49]. Open fractures are associated with more complications than closed fractures [49]. These complications can be mitigated with timely débridement, irrigation, and internal fixation [49]. Fixation of patella fractures is associated with high union rates and low infection rates, but symptomatic hardware and persistent functional deficits can remain a problem postoperatively [70]. Patella baja is associated with poor functional outcomes [70]. Patients treated operatively for patella fractures after total knee replacement had a high complication rate, and surgery on patients with patella fractures should be avoided if possible [10]. Total patellectomy caused relatively higher rates of calcification compared to osteosynthesis with tension band wiring [17]. Recessed or full-length screws may improve stability and bony healing, potentially preventing complications in patella fractures [34]. The treatment of comminuted patella fractures (C3) with a fixed-angle patella plate should be well-considered to avoid distending the indication and biomechanical properties [28].

In patients who experience a patellar fracture after a bone block harvest, clinical outcomes are not significantly different from patients without a fracture at 2-year follow-up [6]. Although rehabilitation was prolonged, the final outcome was not influenced by the patella fracture, with all patients achieving full range of motion and improved knee function in cases associated with medial-third bone-patellar tendon-bone autograft ACL reconstruction [4]. Despite potential complications like tibial tubercle pseudarthrosis and patella fracture, excellent functional outcomes and patient satisfaction can be achieved in cases of spontaneous patella fracture associated with anterior tibial tubercle pseudarthrosis [22]. The effectiveness of arthroscopic all-suture 8-shaped fixation technique for patellar fractures needs to be confirmed by further research [18]. Although it includes inherent risks and limitations, the application of extra-articular arthroscopy with hanger-lifting procedure would help surgeons to treat patellar fracture [15]. These findings have implications on patient morbidity associated with the operative treatment of patellar fractures using metal wire or non-absorbable polyester [5]. Alternative treatments may be effective for management of patella fractures and should be attempted to be popularized in clinic [33]. Anatomical reduction of the articular surface was the most important factor under the control of the surgeon managing a patellar fracture [55]. The consequences of a patellar fracture may be more severe than previously considered, and patients must expect a lifelong increased risk of knee arthroplasty [2]. It is found to be a useful technique for the treatment of comminuted and simple fractures of the patella [23].

Complications

Nonunion and Loss of Reduction: A 2012 meta-analysis of 24 studies involving 737 patellae identified a nonunion rate of 1.9% for surgically managed patella fractures [78]. Loss of reduction and nonunion are recognized complications that contribute to high reoperation rates in patella fracture fixation [155].

Infection: The same 2012 meta-analysis reported infection rates of 3.2% for surgically managed patella fractures [78].

Hardware Complications and Revision: Surgically managed patella fractures are prone to revision surgery, with a reported rate of 33.6% in the 2012 meta-analysis [78]. This high revision rate is driven by the subcutaneous nature of the hardware and the need for early motion to maintain function, which may predispose to hardware loosening [78]. Symptomatic hardware is a frequent complication following open reduction and often requires reoperation for removal [155]. In a 2013 study of 30 patients with isolated unilateral patella fractures, more than one-third elected to have their hardware removed [78].

Functional Outcomes and Pain: Functional outcomes after patella fracture are inferior to population norms regardless of treatment, as found in a 2015 study of 52 displaced fractures [78]. In the 2013 cohort of 30 patients, 24 patients (80%) reported anterior knee pain at 12 months [78]. Patella baja developed in more than half of these patients and is a risk factor for poor functional outcomes after patella fracture surgery [78].

Other Considerations: Surgical management using plating systems or small fragment screws is least associated with postoperative complications [7], and locked plating is associated with low complication rates [29]. Total patellectomy for highly comminuted fractures caused relatively higher rates of calcification compared to osteosynthesis with tension band wiring [17]. Disuse osteoporosis of the patella can result from non-operative treatment in a plaster cylinder and may lead to subsequent refracture, which may occur at a different site than the original injury [84]. Patients with a history of patella fracture are at increased risk of early surgery-related complications after total knee arthroplasty [32], and those treated operatively for patella fractures after total knee replacement had a high complication rate [10]. Secondary resurfacing of the patella for residual anterior knee pain after total knee arthroplasty is associated with a higher rate of complications, including patellar fracture and postoperative stiffness [135]. A complication rate of 20.3% was reported after medial patellofemoral ligament reconstruction using two transverse patellar tunnels, with patellar fracture being a specific risk factor associated with male gender [124].

Recovery

Light activity (weeks): The provided evidence does not specify a typical week range for the resumption of desk work, driving, or light activities of daily living.

Full activity (months): The provided evidence does not specify a month range for the return to manual work, sport, or full range of motion and strength.

Complete recovery / outcome plateau (months): The provided evidence does not specify a month range for the stabilization of pain, strength, or final functional outcomes.

Rehabilitation protocol: The provided evidence does not detail specific physical therapy phasing, immobilisation duration, weight-bearing or range-of-motion progression schedules, or timing for sling or brace removal.

Functional milestones: Patient-reported outcomes and objective functional testing show significant improvement over the study period in both plating and tension band groups [78]. In a 2017 prospective cohort study, the plate construct group demonstrated statistically significant greater improvement in Knee Outcome Survey Activities of Daily Living Scale scores compared with the tension band group [78]. Patients in the plating group also showed significantly greater improvement in several objective functional testing outcomes and greater thigh circumference compared with the tension band group [78]. In a 2013 study of 30 patients, residual deficits in muscle performance and functional ability persisted 12 months after surgical intervention [78].

Other Considerations: Long-term outcomes after patella fractures are generally poor, with outcome scores considerably poorer than normalized population values [78]. A 2012 meta-analysis of 24 studies involving 737 patellae found nonunion rates of 1.9%, infection rates of 3.2%, and revision surgery rates of 33.6% for surgically managed patella fractures [78]. Surgically managed patella fractures are prone to revision surgery due to the subcutaneous nature of the hardware and the need for early motion, which may predispose to hardware loosening [78]. In a 2013 study of 30 patients, 24 patients (80%) reported anterior knee pain, and more than one-third of all patients elected to have their hardware removed [78]. Patella baja developed in more than half of the patients in this 2013 cohort, which is a risk factor for poor functional outcomes [78]. In contrast, a 2017 study found that none of the 25 patients treated with a novel plating technique required hardware removal for pain relief, and these patients had significantly less anterior knee pain at 12 months compared with the cohort treated with a traditional tension band construct [78]. A 2015 study of 52 displaced patella fractures noted no difference in union rates, complication rates, ROM, or outcome measures between open reduction and internal fixation or partial patellectomy, though functional outcomes were inferior to population norms regardless of treatment [78]. Patellar fractures are associated with an increased risk of total knee arthroplasty, and patients must expect a lifelong increased risk of knee arthroplasty [2]. In elderly patients above 65 years, the relative risk of death was 0.9, indicating that patella fractures were not associated with an increased mortality rate [51].

Regarding specific injury contexts, although rehabilitation was prolonged for patellar fractures associated with medial-third bone-patellar tendon-bone autograft ACL reconstruction, the final outcome was not influenced by the patella fracture, with all patients achieving full range of motion and improved knee function [4]. The prognosis of complex knee injuries with a combination of ligamentous injuries and associated fractures is much worse when compared to either injury alone [50]. Despite potential complications like tibial tubercle pseudarthrosis and patella fracture in a revised knee replacement following knee arthrodesis, excellent functional outcomes and patient satisfaction can be achieved [22]. Patellar fracture after total knee arthroplasty with retained patella is infrequent, with relatively improved clinical and radiological results compared with those of patellar fracture after total knee arthroplasty with resurfaced patella [25]. The 10-year survivorship free of any revision and any reoperation after intraoperative periprosthetic patellar fractures was 88% [174].

Key Evidence

• [L4] Understanding the etiologic factors leading to atraumatic patellar fractures could result in minimizing complications. [1] (10.1097/01.blo.0000218722.83601.18)
• [L2] The consequences of a patellar fracture may be more severe than previously considered, and patients must expect a lifelong increased risk of knee arthroplasty. [2] (10.1302/0301-620x.100b11.bjj-2018-0312.r2)
• [L4] Patellar fractures in the female and elderly populations are increasing. [3] (10.1016/j.injury.2019.10.016)
• [L4] Although rehabilitation was prolonged, the final outcome was not influenced by the patella fracture, with all patients achieving full range of motion and improved knee function. [4] (10.1007/s001670100207)
• [L4] These findings have implications on patient morbidity associated with the operative treatment of patellar fractures. [5] (10.1016/s0020-1383(00)00170-4)
• [L4] In patients who experience a patellar fracture after a bone block harvest, clinical outcomes are not significantly different from patients without a fracture at 2-year follow-up. [6] (10.1177/2325967119829051)
• [L3] Surgical management of patellar fractures remains crucial but fracture fixation using plating systems or small fragment screws is least associated with postoperative complications. [7] (10.1186/s12891-023-06998-3)
• [L4] Displaced patella fractures with extensor mechanism disruption generally require operative treatment to maximize long-term outcomes. [8] (10.1055/s-0033-1353988)
• [L3] Patients treated operatively had a high complication rate, and surgery on patients with patella fractures should be avoided if possible. [10] (10.1097/01.blo.0000092992.90435.20)
• [L4] The presence of an isolated medial fragment serves as an indicator of increased risk for postoperative lateral patellar displacement. [11] (10.1186/s13018-026-06807-2)
• [L5] Arthroscopically assisted percutaneous fixation of a patellar fracture offers the treating surgeon and patient a viable option for restoration of the articular surface without the inherent risks of an open incision. [14] (10.1016/j.eats.2022.12.010)
• [Paper] Although it includes inherent risks and limitations, this new application of arthroscopy would certainly help surgeons to treat patellar fracture. [15] (10.1016/j.eats.2013.03.002)
• [L3] Total patellectomy technique was a safe and reliable alternative treatment for treating patients with highly comminuted patella fractures when anatomically reduction and rigid fixation were difficult, although it caused relatively higher rates of calcification. [17] (10.1186/s13018-021-02656-3)
• [L5] However, its effectiveness in fixing patellar fractures needs to be confirmed by further research. [18] (10.1016/j.eats.2025.103780)
• [L4] In comminuted inferior pole fractures of the patella, suture bridge anchor fixation showed good bony union and satisfactory clinical outcomes at short-term follow-up and could be a satisfactory alternative treatment option. [20] (10.1007/s00402-020-03671-5)
• [L4] Generally, undisplaced peri-prosthetic patella fractures should be treated nonoperatively whenever possible. [21] (10.1186/s42836-020-00050-8)
• [L5] Despite potential complications like tibial tubercle pseudarthrosis and patella fracture, excellent functional outcomes and patient satisfaction can be achieved. [22] (10.1186/1471-2474-14-317)
• [Paper] It is found to be a useful technique for the treatment of comminuted and simple fractures of the patella. [23] (10.1016/j.otsr.2010.01.014)
• [L4] The method preserves the patella intact when principal fragments are present, though partial patellectomy may be required for comminuted fractures with unreducible small fragments. [24] (10.2106/00004623-198769010-00014)
• [L4] Patellar fracture after TKA with retained patella is infrequent, with relatively improved clinical and radiological results compared with those of patellar fracture after TKA with resurfaced patella reported in the literature. [25] (10.1016/j.arth.2021.03.053)
• [L4] The treatment of comminuted patella fractures (C3) with a fixed-angle patella plate should be well-considered to avoid distending the indication and biomechanical properties. [28] (10.1016/j.injury.2016.06.018)
• [L4] Locked plating of patella fractures is a reliable alternative treatment with good functional outcomes, low complication rates and high patient satisfaction. [29] (10.1177/2325967117s00138)
• [L5] [30] (10.5435/jaaos-d-20-00591)
• [L4] Transverse fracture of the patella is a rarity in children under 15 years, contrary to general belief in textbooks. [31] (10.1007/bf00452971)
• [L3] Patients with a history of patella fracture are at increased risk of early surgery-related complications after TKA. [32] (10.5435/jaaosglobal-d-24-00007)
• [L1] Alternative treatments may be effective for management of patella fractures and should be attempted to be popularized in clinic. [33] (10.1186/s13018-018-0919-6)
• [L5] Recessed or full-length screws may improve stability and bony healing, potentially preventing complications in patella fractures. [34] (10.1186/s13018-025-05567-9)
• [L3] Although postoperative complication rates are not increased by the use of transosseous wire fixation in patellar fractures, no significant benefits are provided by this technique in terms of functional scores, knee range of motion, or the rate of fracture healing. [35] (10.1186/s12891-025-09228-0)
• [L3] Open patellar fractures are high energy injuries associated with significantly higher rates of associated injuries compared to closed fractures. [36] (10.1016/j.injury.2007.10.032)
• [Paper] [37] (10.1097/corr.0000000000003544)
• [L4] Sleeve fractures of the patella can occur at the superior pole but are typically located at the inferior pole. [40] (10.1177/0363546510374448)
• [L3] CT imaging enhances the classification and mapping of patellar fractures, highlighting the central patella as the primary site of injury. [43] (10.3390/jcm14041335)
• [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. [44] (10.2106/00004623-199511000-00012)
• [L3] Although PCL injuries requiring surgery are rare, 25% of patients requiring surgery for patellar fractures presented with a PCL injury. [47] (10.1007/s00402-016-2449-1)
• [L5] [49] (10.5435/00124635-201104000-00004)
• [L4] The prognosis of such complex knee injuries with combination of ligamentous injuries and associated fractures is much worse when compared to either injuries alone. [50] (10.1007/s00167-007-0431-8)
• [L2] In elderly patients above 65 years, the relative risk of death was 0.9, indicating that patella fractures in elderly patients were not associated with an increased mortality rate. [51] (10.1016/j.injury.2018.07.003)
• [L3] The biomechanical properties of the fixed-angle plate seem promising and convincing in providing a rigid and stable fixation method for transverse patella fractures. [52] (10.1016/j.injury.2012.04.020)
• [L3] Anatomical reduction of the articular surface was the most important factor under the control of the surgeon managing a patellar fracture. [55] (10.1016/j.injury.2005.12.017)
• [L4] Arthroscopically assisted techniques for minimally invasive fixation of patellar fractures represent a reliable option. [57] (10.1016/j.otsr.2017.04.010)
• [L4] [75] (10.1016/j.injury.2016.05.039)
• [L3] It is a safe alternative surgical technique in fixation of patellar fractures. [77] (10.1186/s12891-025-08975-4)
• [L4] Open reduction and internal fixation should be considered for traumatic periprosthetic patellar fractures with good remaining bone stock, as internal fixation is a viable option for this subset of patients and alternative interventions like patellectomy are associated with significant long-term morbidity. [81] (10.1097/01.blo.0000162999.01156.d1)
• [L5] [83] (10.2106/jbjs.20.01478)
• [L4] [84] (10.1016/0020-1383(85)90086-5)
• [L3] Native patellar thickness was inversely correlated with fracture risk, while lateral positioning during resurfacing and increased component size were associated with increased risk. [87] (10.1016/j.arth.2026.03.079)
• [L5] [111] (10.5435/00124635-199711000-00004)
• [L3] The turned-over patella operation method exhibited some superiority to conventional reduction-fixation approach for treatment of C3-type patellar fractures in terms of efficacy and safety by enlarging the ROM of the knee joint and promoting functional recovery. [114] (10.1016/j.injury.2019.03.028)
• [L4] The new tension band fixation technique using braided polyblend sutures resulted in good outcomes and is considered clinically effective for patellar fracture reduction. [123] (10.1016/j.injury.2008.10.032)
• [L4] The study reports a complication rate of 20.3% after MPFL reconstruction using two transverse patellar tunnels, with patellar fracture being a specific risk factor associated with male gender. [124] (10.1007/s00167-016-4245-4)
• [L3] The loop anchor tension band technique is safe and effective for treating patella fractures. [126] (10.1016/j.injury.2020.11.057)
• [L4] It may be an effective fixation method for treating displaced, comminuted inferior pole fracture of the patella. [128] (10.1007/s00402-017-2807-7)
• [Paper] [155] (10.1016/j.eats.2021.02.008)
• [L4] Patellar fractures in the elderly were mostly from low-energy injuries, with CT images demonstrating high rates of inferior pole involvement and comminution. [160] (10.1007/s00402-020-03526-z)
• [L4] The 10-year survivorship free of any revision and any reoperation after intraoperative fractures was 88%. [174] (10.1016/j.arth.2026.05.003)

See Also

• Total Knee Replacement
• ACL reconstruction

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