Managing patellofemoral instability in in-season athletes: a review

Introduction

Patellofemoral instability (PFI), a condition characterized by lateral dislocations or subluxations of the patella, is a significant issue for in-season athletes. This condition primarily affects young, active individuals, particularly those involved in sports that require pivoting, jumping, or sudden directional changes. Sports like football, basketball, and soccer have particularly high incidences of PFI due to the repeated stress placed on the knee joint (1,2). Research suggests that 55% to 61% of first-time lateral patellar dislocations occur during athletic activity, with adolescents being the most vulnerable population (3). The overall injury rate is approximately 1.95 per 100,000 athlete exposures, with higher rates in sports like gymnastics, football, and wrestling (4). Despite the high incidence of these injuries, in-season management poses unique challenges, as athletes often face pressures to return to play (RTP) quickly.

The complexity of PFI stems from the multifactorial nature of its etiology. While patellar dislocations can impact those without any underlying risk factors, abnormalities such as trochlear dysplasia, patella alta, an increased tibial tubercle-trochlear groove (TT-TG) distance, lateral patellar tilt, valgus alignment and rotational abnormalities significantly increase the risk of recurrent dislocations (5). Studies show that patients without risk factors have a lower recurrence rate of patellar dislocation, ranging from 7.7% to 31.2% (6-8). The likelihood of redislocation rises to 22.7–36.6% with one risk factor, 50.9–71.7% with two risk factors, and 74.8–86.2% when three risk factors are present (6). Additionally, skeletal immaturity, ligamentous laxity, previous dislocations, and muscular imbalances contribute to ongoing PFI (9).

Diagnosis and evaluation

Clinical examination

A comprehensive history and physical examination are crucial in diagnosing PFI. Patients typically describe pain and deformity of the knee following a direct blow to the anterior or medial aspect of the knee, or a non-contact twisting injury. Pertinent history includes any previous knee ligamentous injury or laxity in addition to record of any prior dislocations or instability events (10,11). For an acute dislocation, effusion or hemarthrosis is a typical finding, but this is less likely in the case of chronic dislocation (12). Physical examination also focuses on assessing patellar tracking, translation, tilt, tenderness, range of motion (ROM), and ligamentous laxity. More specific findings on exam to indicate PFI include tenderness over the medial patellofemoral ligament (MPFL) and retinaculum, which is seen more in acute patellofemoral dislocation/subluxation; there may also be increased lateral translation of the medial border of the patella relative to the lateral edge of the trochlea when compared to the contralateral (uninjured) side, as quantified by quadrants of the patella (10). Lateral displacement of the patella when the knee is flexed between 20 to 30 degrees is a strong indicator of instability, and it helps evaluate the integrity of the MPFL, one of the primary restraints of the patella, which is frequently damaged in lateral patellar dislocations (5,13).

Patellar tilt refers to the angular orientation of the patella in relation to the trochlea Excessive patellar tilt is a key factor in patellar instability, as it can disrupt normal tracking within the trochlear groove, increasing the risk of subluxation or dislocation (14). The medial tilt test assesses patellar tilt reducibility by applying a medial force to the lateral edge of the patella while the patient lies supine with the knee extended. A positive test indicates lateral retinacular tightness, while a negative test suggests the patella can correct medially; however, it is consistently negative in high-grade trochlear dysplasia due to structural abnormalities (15).

Clinical signs, including the apprehension sign and J-sign, should also be examined. A positive apprehension sign occurs when a patient presents with guarding or lack of firm endpoint with passive lateral translation (10,16). The J-sign refers to the inverted “J” path the patella takes from extension to early flexion in a maltracking patella, marked by the presence of a visible shift when the subluxated patella engages the trochlear groove (17). Further clinical examination should also involve assessing the alignment of the lower extremity, as rotational and coronal plane malalignments often contribute to instability (1,18,19). Evaluating standing alignment and hip-thigh angle are important aspects of the clinical exam, as increased femoral anteversion and valgus alignment increase lateral patellar instability (20). Any of these findings are indicative of PFI and warrant imaging for further evaluation.

Imaging modalities

Imaging plays a vital role in diagnosing PFI and in planning treatment strategies. Radiographs are the first step and are commonly used to assess bone structure and alignment. Anteroposterior and lateral views can reveal patella positional abnormalities or trochlear dysplasia, while the Merchant view is useful for evaluating patellar tilt and positioning within the trochlear groove (12). The lateral view is particularly important, as it can be utilized for assessment of patellar height. In cases of PFI, the patella is usually high-riding in a condition known as patella alta. This results in decreased contact area between the patella and trochlea of the femur lending itself to higher risk of instability, as the patella does not engage the trochlea until higher degrees of flexion (21). Validated ratios, such as the Insall-Salvati and Caton-Deschamps ratios, can be calculated from measurements on lateral radiographs and can provide an idea about the level of the patella relative to the joint line (Figure 1) (22,23). Ideally, these ratios should be calculated with the knee in 30 degrees of flexion; normal value for the Insall-Salvati ratio is between 0.8 and 1.2, and normal for Caton-Deschamps is between 0.6 and 1.3 (22). Furthermore, the lateral view can be used to evaluate trochlear dysplasia and look for a supratrochlear spur. Signs affiliated with dysplasia include the crossing sign and the double contour sign. For the crossing sign, the trochlear groove lies in the same plane as the anterior border of the lateral femoral condyle, representing a flat trochlear groove. As for the double contour sign, the anterior border of the lateral femoral condyle lies anterior to the anterior border of the medial femoral condyle, which represents a convex trochlear groove/hypoplastic medial femoral condyle (24).

Figure 1 Insall-Salvati and Caton-Deschamps measurements for patella alta. Insall-Salvati method: the ratio A/B is used to assess patella alta. Line A is the distance from the insertion point of the patellar tendon on the inferior patella to the superior edge of its insertion on the tibial tuberosity. Line B is the distance from the most superior subchondral bone of the patella to the point where the patellar tendon inserts on the inferior patella. Caton-Deschamps method: the ratio C/D is used for this measurement. Line C is the distance from the inferior edge of the patellar cartilage’s articular surface to the anterior corner of the superior tibial joint surface. Line D is measured from the superior to the inferior aspects of the patellar cartilage’s articular surface. This figure was reused/adapted from an open access article (22) under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).

The Merchant view is a widely utilized radiographic technique obtained for the purposes of assessing the trochlea, the patellar tilt and lateralization. This view is obtained with the patient supine with the knee flexed to 45 degrees while the x-ray beam is inclined downward at 30 degrees (25). Findings of lateral patellar tilt on the Merchant view is sensitive for patellar instability. The severity of patellar tilt can be further evaluated by using the congruence angle, which is the angle formed between the bisector of the trochlea and a line that connects the central ridge of the patella and the deepest part of the trochlear sulcus. In normal knees, the ridge of the patella is medial to the sulcus’ bisector, which in normal knees, should be a negative value (26). However, if a Merchant radiograph is not executed precisely, it may present a distorted image, making it challenging to evaluate the depth of the trochlea accurately. This limitation makes magnetic resonance imaging (MRI) or computed tomography (CT) scans more reliable for assessing the trochlea due to their ability to provide a more detailed and accurate view of the anatomy (27).

The frontal mechanical axis should also be assessed using standardized weight-bearing full-leg radiographs, measuring the angle between the mechanical femoral and tibial axes. Positive values indicate a varus (inward) alignment, while negative values indicate a valgus (outward) alignment (28). The quadriceps angle (Q angle) reflects the alignment of the extensor mechanism, which includes the quadriceps, patella, and tibial tubercle. It helps evaluate the forces affecting patellofemoral tracking. The Q angle is formed by the lines drawn from the anterior superior iliac spine to the patella’s center and from there to the tibial tubercle. When measured in the supine position, the Q angle is slightly lower compared to measurements taken in standing radiographs, so this must also be taken into consideration (29).

For more detailed analysis of the patellofemoral joint, CT has been used historically to measure TT-TG; the TT-TG distance quantifies the horizontal distance between the tibial tubercle (the point of patellar tendon insertion) and the deepest point of the trochlear groove (the center of the femoral trochlea) (Figure 2). However, MRI is being increasingly accepted as the standard imaging technique for TT-TG distance, which is critical for determining whether surgical correction, such as tibial tubercle osteotomy (TTO), is necessary (9). TT-TG distance greater than 20 mm is often considered abnormal and may indicate a predisposition to patellar instability; thus, a previous study advocated for this distance as justification for a medializing TTO; however, two other recent studies recommended 15 mm as a threshold for a medializing TTO (30-32). One recent meta-analysis suggested 12.5 mm as the cut-off on MRI, as MRI tends to underestimate TT-TG distance compared to CT, which needs to be taken into consideration during surgical planning (33).

Figure 2 Measurement of the tibial tuberosity-trochlear groove distance. The tibial tuberosity-trochlear groove distance, labeled as C, is measured using superimposed axial images. Baseline F is drawn along the posterior femoral condyles. Line A is perpendicular to baseline F and intersects the deepest point of the trochlear groove. Line B, also perpendicular to baseline F and parallel to line A, passes through the center of the tibial tuberosity. The distance between lines A and B is recorded as distance C. This figure was reused/adapted from an open access article (22) under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).

Sagittal patellofemoral engagement (SPE) refers to the interaction between the patella and the femoral trochlea in the sagittal plane, which is essential for patellar stability (34). The SPE index, an MRI-based measurement, calculates the ratio of trochlear cartilage length (TL) to patellar cartilage length (PL), providing a more precise evaluation than traditional radiographic methods (35). This ratio, SPE = TL/PL, offers valuable insight into patellofemoral engagement, particularly in cases of maltracking, trochlear dysplasia, or suspected instability. Studies indicate that patients with patella alta have a lower SPE, reflecting reduced functional engagement and a higher risk of instability (34,35). As a supplementary tool, the SPE enhances patellar height assessment and maltracking evaluation, particularly when instability occurs without obvious patella alta. By offering a detailed analysis of functional engagement, this method may help reassess the need for tibial tuberosity osteotomy in select patients (35).

Furthermore, MRI plays a crucial role in visualizing the cartilaginous surfaces of the patellofemoral joint and is highly sensitive in detecting concomitant injuries, including cartilaginous, ligamentous, capsular, and bony lesions associated with patellar instability events (36). The Sillanpää classification system, which categorizes MPFL avulsion injuries via MRI findings, helps assess injury severity and guide treatment decisions (37). It classifies injuries at the patellar attachment into three types: P0 (ligamentous disruption without bone involvement), P1 (bony avulsion fracture), and P2 (bony avulsion with articular cartilage involvement, often requiring surgical fixation) (37).

Chondral injuries are a serious complication of PFI as a result of patellar maltracking or frank dislocation; thus, their presence may require surgical intervention. Compared to the trochlear groove, the patella exhibits a higher incidence of chondral injuries, and more severe chondral injuries have been correlated with greater patellar tilt angle (38). MRI is able to show discrete chondral defects and varying degrees of cartilage loss in order to guide management and combat the long-term negative consequences of cartilage damage, mainly knee osteoarthritis. Together, clinical examination and imaging provide a comprehensive picture of the patient’s patellofemoral joint health, allowing for personalized treatment plans that address both anatomical and functional aspects of the injury.

Non-surgical treatment

Indications for non-operative management

In athletes with PFI, operative versus non-operative management is based on a multitude of factors. Non-operative management remains the first line of treatment for most in-season athletes presenting with PFI, particularly following a first-time dislocation and when there are no significant anatomical abnormalities or osteochondral damage (18,39-41). However, major factors that should be taken into consideration include the number of dislocation events the athlete has had, age of the athlete, any presence of osteochondral injury, and any previous treatments (42).

Following a thorough assessment, if non-operative management is chosen, activity modification, treatment modalities and RTP guidelines can all be utilized to optimize treatment and enable safe return to sport participation.

Primary considerations

The primary goals of non-operative management are to reduce pain, minimize inflammation, and restore the athlete’s strength, ROM and functional stability (39). Following acute patellar dislocation, management of pain and swelling, as well as activity modification are the first line of treatment (43). Adjusting training intensity and modifying activities to minimize patellofemoral stress is crucial in the initial phase of management. Swelling has been proven to have a deleterious effect on quadriceps activity, thereby affecting overall recovery and ROM (43-45). Pharmacotherapy such as oral analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) can provide short-term pain relief and reduce inflammation. Ice is most effective in the first two to three days following the acute injury (43). In some cases of moderate and severe effusions, aspiration of the joint effusion is warranted to improve patient comfort and start early ROM (46). Additionally, activity modification can prove helpful as part of the treatment process. The necessity and optimal method of immobilization for non-operative treatment of first-time patellar dislocation (FTPD) remain subjects of ongoing debate (40,47,48).

Once pain and swelling have been addressed, therapy should focus on regaining strength, full knee ROM, and proprioception, or good control of the lower extremity throughout ROM (43,44). A tailored exercise program focusing on strengthening the quadriceps, hip abductors, and core muscles can improve patellar tracking and dynamic stability (49). Neuromuscular re-education emphasizing proper landing mechanics and movement patterns is vital. Therapy should begin initially with muscle-building exercises with closed-chain kinematics, such as leg press, as these exercises have been proven to be safer, more effective, and provide faster and stronger activation of the vastus medialis oblique (VMO) muscle, which is a dynamic stabilizer of the patella (50-53). Other activities during therapy should also focus on addressing strength deficits, promote muscle activation, and involve functional and neuromuscular training (54,55). Utilizing closed chain exercises from 0 to 50 degrees and open chain exercises from 5 to 90 degrees of knee flexion have been shown to help regain proximal strength and decrease the load on the anterior knee structures (56). Patients with patellofemoral pain have also been found to have decreased flexibility both proximally and distally to the knee, and this should also be addressed if noted during the athlete’s rehabilitation (57). Additional modalities of therapy proven to be useful are the use of a vibrating plate, which has a positive effect on muscle building and preservation (58).

Taping and bracing

Patellar taping is believed to enhance patellofemoral tracking; a few MRI studies have shown that patellar taping can reduce patellofemoral malalignment, although this finding is contested by other research (59-61). While it is not commonly employed as a primary treatment, a six-week taping regimen has been described for the rehabilitation phase following non-surgical treatment. This approach facilitates early functional rehabilitation, is easy to apply, and is cost-effective, though it can cause minor skin irritation (62). In a small trial, 18 patients were randomized to receive either a tape bandage or a cylinder cast. Taping led to significantly better Lysholm scores at 6 and 12 weeks (P=0.001), with the improvement persisting through 5 years of follow-up (P=0.008). No cases of re-dislocation were reported, though the small sample size limits the ability to draw definitive conclusions (62). In female soccer players specifically, it has also been reported that a significant decrease in patellofemoral pain was associated with using a knee sleeve or kinesiology tape compared to no supportive device (63,64).

Regarding bracing, a 2012 systematic review identified only one relevant study that compared non-operative management using a cylinder cast, brace, or posterior splint (47). This review, as well as a more recent review in 2019, concluded that the currently available literature on conservative management after a first time patellar dislocation is scarce, and of low quality, and conclusions should be interpreted cautiously (47,61). A separate, well-cited study found a significantly higher re-dislocation rate in the brace group (0.29 per follow-up year) compared to the cylinder cast and posterior splint groups (0.12 and 0.08 per follow-up year, respectively, P<0.05) (40). However, the evidence quality was considered low due to a small sample size, variations in immobilization duration between groups, and the use of outdated brace models. The 2024 European Society of Sports Traumatology, Knee Surgery and Arthroscopy (ESSKA) consensus guidelines subsequently stated there is no strong evidence supporting the superiority of any bracing method over no bracing in FTPD, either in the acute or non-acute phase. While short-term bracing with unrestricted motion may be considered immediately after injury, prolonged immobilization can lead to muscle atrophy and reduced knee function, with no clear advantage in preventing redislocation over functional mobilization (48).

Sports-specific rehabilitation

As the patient progresses through rehabilitation and achieves pain reduction, strength restoration, and improved ROM, the focus shifts toward sport-specific exercises to reintroduce the athlete to competition (65). This transition typically begins around 4–8 weeks, depending on individual progress, clinical benchmarks, and functional assessments (65). Before returning to running and high-impact activities, athletes should demonstrate strength symmetry within 20% of the unaffected limb and good motor control, particularly during double- and single-leg hopping tests, as neuromuscular deficits increase the risk of reinjury and recurrent instability (66,67).

A gradual, structured return-to-sport protocol is critical for a safe reintegration into sport, incorporating progressive strength training, agility drills, plyometrics, and change-of-direction exercises to simulate sport-specific movements (2,68). Functional assessments such as hop testing, lower extremity strength testing, and patient-reported outcome measures are essential for determining readiness to RTP (65). Additionally, quadriceps and hip muscle strengthening, as well as proprioceptive training, play a key role in optimizing knee stability and reducing the risk of recurrent patellar instability (67).

Rehabilitation should also emphasize neuromuscular control, psychological readiness, and progressive functional movements, as confidence in knee stability is a key factor in successful return to competition (67). Studies indicate that while some athletes may return to sport within 3–4 months, full return to pre-injury performance levels often takes closer to 6–9 months, depending on sport demands and individual recovery rates (2,69). Ensuring proper strength, movement mechanics, and mental preparedness helps minimize reinjury risk and facilitates a successful and sustainable return to high-level competition (65).

Risk of recurrence

It should be noted that recurrence rates can be significant, even with appropriate non-operative management. For instance, a study involving over 2,000 patients found that 30.6% of first time dislocators managed non-operatively experienced recurrent PFI, with nearly half of these cases eventually requiring surgical intervention (70). Another study reported a recurrence rate of 34.7% in children and adolescents treated non-operatively after a first-time dislocation (8). These findings suggest that while non-operative management can be effective for some, a substantial proportion of patients may experience recurrent PFI.

Additionally, age is a critical factor influencing the recurrence of PFI. Younger patients, particularly those under 25 years, are at a higher risk of recurrence. For example, patients younger than 25 years with trochlear dysplasia have a 60–70% risk of recurrence within 5 years (70). Similarly, another study found that patients aged 14 years and below had a significantly higher risk of recurrence, with skeletal immaturity being a notable risk factor (8). In adolescents, younger age at the time of surgery was associated with a higher likelihood of recurrent PFI, with each additional year of age decreasing the odds of failure by 23% (71). However, this does not suggest that younger patients should avoid surgery, but rather that their higher risk of recurrence should be carefully considered when planning treatment and post-surgical rehabilitation.

Furthermore, despite non-operative management decreasing incidence of recurrent dislocation, between 30% and 50% of patients who experience an initial patellar dislocation may continue to experience symptoms of PFI and/or anterior knee pain (72). All of these factors should be considered when determining the appropriate timing and necessity of surgical intervention for an athlete with PFI.

Surgical treatment

Indications for surgery

Surgical intervention is typically indicated for athletes with osteochondral fractures/loose bodies causing mechanical symptoms, recurrent patellar dislocations, significant anatomical abnormalities, or failure of non-operative management. Specifically, MPFL avulsion injuries with significant articular cartilage involvement (Sillanpää P2 type injury) warrant surgical repair to restore cartilage integrity (37). Failure of non-operative management of PFI would entail persistent pain around the patella, a subjective feeling of the knee “giving way” or instability, difficulty with activities that involve bending the knee, and potentially a significant limitation in daily function despite treatments like physical therapy and pain medication (73). Usually, this is determined over the course of 3–6 months (74).

Common anatomical factors necessitating surgery include increased TT-TG distance, patella alta, and trochlear dysplasia (5). In such cases, surgery offers the best chance to ensure long-term stability of the patella and reduce the risk of future dislocations (75).

Operative management of PFI has demonstrated high rates of RTP with low recurrence rates across multiple studies evaluating athletes in various sports (2,65,72,75). Surgically treated athletes typically experience a longer recovery period before returning to play, and in some cases, surgery may be postponed until after the season if the athlete can continue competing with non-operative management. Surgical intervention, whether performed mid-season or post-season, has been associated with lower rates of recurrent instability, improved long-term knee stability, and a higher likelihood of completing future seasons (76,77). However, bony procedures in skeletally immature patients, particularly young athletes, require caution due to open growth plates, which restrict the use of osteotomies and other physeal-disrupting techniques. Instead, surgical management has shifted toward soft-tissue procedures, such as MPFL reconstruction, to restore patellar stability while preserving growth plate integrity (41,78). Given the risk of growth disturbances, treatment should be individualized.

MPFL reconstruction

The MPFL is the primary static restraint against lateral displacement of the patella during the first 30 degrees of knee flexion (79). Injuries to this ligament are almost universally seen in patellar dislocations, which makes MPFL reconstruction a key surgical intervention for patients with recurrent instability (12). MPFL reconstruction is considered the standard of care in cases where non-surgical treatments fail, and it is particularly effective in younger, athletic populations (9,22,39). MPFL repair is an option for first time dislocators undergoing surgery in the acute setting, such as in the instance of concomitant osteochondral fracture. However, several studies have looked at repair versus reconstruction for recurrent patellofemoral dislocations; one study recently found MPFL repair resulted in a nearly 3-fold higher rate of recurrent patellar dislocation (41% vs. 14%) at the long-term follow-up compared with MPFL reconstruction (80). MPFL reconstruction involves using either an autograft or an allograft, both of which have been shown to yield comparable outcomes in terms of stability and function (81). The procedure stabilizes the patella by anchoring the graft at the femoral attachment of the original ligament, restoring normal patellar kinematics. Both single bundle and double bundle MPFL reconstructions have been described, with recent literature indicating better graft stability, improved patella stability, and improved clinical outcomes with double bundle MPFL reconstruction (82).

Studies show that MPFL reconstruction allows a high rate of return to sport, with approximately 92.8% of athletes returning to activity, and 71.3% returning to or surpassing their preoperative levels in a recent meta-analysis (45,75,83). Furthermore, the recurrence rate of patellar instability following MPFL reconstruction is low, approximately 1.9%, making it a highly effective option for athletes (75). While MPFL reconstruction alone can correct PFI in many cases, it is not always sufficient for patients with severe bony abnormalities. For example, in cases where the TT-TG distance is greater than 15 mm, a more aggressive procedure like TTO may be needed in addition to MPFL reconstruction.

Osteotomies

When PFI is associated with abnormal lateralization of the tibial tubercle, TTO is often performed alongside MPFL reconstruction (5,42). Abnormal lateralization is measured by the TT-TG; as previously discussed, a TT-TG distance greater than 20 mm is commonly considered abnormal and the threshold used for electing to perform a TTO, though recent studies have advocated for the threshold to be 15 mm (30-32). This procedure repositions the tibial tubercle to align the extensor mechanism and reduce the lateral forces acting on the patella (84). The most common procedure is the anteromedializing (AMZ) TTO, which has been a reliable method for improving extensor mechanism tracking. Additionally, distalization of the patella may be indicated when pathological patella alta is present; this can be done in isolation or in combination with anteriorization and medialization (85). However, during distalization TTOs, fully detaching the tibial tubercle carries a significantly higher risk of nonunion and tibial fracture compared to other TTO techniques (86). TTO is a more invasive procedure than MPFL reconstruction and requires a longer recovery time due to the bone healing required after the transfer. However, it significantly improves outcomes in patients with severe malalignment, and has a high rate of return to sports, with one retrospective case series showing an 83.3% return to at least one sport, with many returning to the same or higher level of intensity (87,88). Research shows that combining MPFL reconstruction with TTO can restore normal patellar kinematics and prevent future dislocations, especially when isolated MPFL reconstruction may not be sufficient (12,39,84).

For completeness, we will briefly explore derotational distal femur osteotomies, though their outcomes in athletic populations remain unstudied (89). Given the lack of data on return-to-sport rates, this procedure may be best suited for individuals with severe instability who are unlikely to resume competitive play. A biplanar supracondylar torsional osteotomy of the femur is performed, using a controlled cut in the distal part of the femur (just above the knee) to achieve the desired rotational correction when viewed from an axial perspective. In patients with both PFI and increased femoral anteversion, derotational distal femur osteotomy resulted in a significant reduction in pain, improved subjective knee function, and effective correction of both torsional and coronal alignment (89).

Trochleoplasty

For patients with severe trochlear dysplasia, where the femoral trochlea is too shallow or misshapen to provide adequate patellar tracking, trochleoplasty may be indicated. These patients typically display the J-sign on exam. This procedure reshapes the trochlea to create a deeper groove, allowing the patella to sit more securely during knee flexion. Trochleoplasty is typically reserved for severe dysplasia cases, such as Dejour Type D, where other interventions like MPFL reconstruction or TTO may not sufficiently address the underlying problem (Figure 3) (16,75,84). Three main types of trochleoplasties have emerged: lateral facet elevation, recession wedge, and sulcus deepening (90). Of these, two deepening trochleoplasties that are frequently employed are the “U-shaped” deepening trochleoplasty and the “V-shaped” deepening trochleoplasty (91). The “U-shaped” deepening trochleoplasty is where a thin osteochondral flap is lifted and is subsequently repositioned into the reshaped bony bed and secured with suture (92). The “V-shaped” deepening trochleoplasty aims to reduce trochlear prominence and create a new “V-shaped” groove with normal depth, thereby improving patellar tracking (91,92). The “U-shaped” deepening trochleoplasty is now the most frequently used and has shown the lowest rate of recurrence and postoperative ROM deficiency (91).

Figure 3 Dejour trochlear dysplasia classification. Dejour’s classification of trochlear dysplasia is as follows: Grade A: characterized by a crossing sign [1] on a lateral radiograph and a shallow trochlear sulcus on axial imaging, with an angle greater than 145°. Grade B: identified by a supratrochlear spur [2] on a lateral radiograph and a flat trochlea on axial imaging. Grade C: defined by a double contour [3] on a lateral radiograph, medial condyle hypoplasia, and convexity of the lateral trochlea on axial imaging. Grade D: involves both a double contour [3] and a supratrochlear spur [2] on a lateral radiograph, along with severe trochlear asymmetry, where a “cliff” [4] separates the medial and lateral condyles. This figure was reused/adapted from an open access article (22) under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).

This procedure is primarily indicated for patients with severe trochlear dysplasia and recurrent PFI, especially when other surgical interventions have failed (90). High-grade trochlear dysplasia can prevent athletes from competing in high-level sports, and surgery is often career-ending or significantly restricts their ability to compete at an elite level. Careful patient selection based on clinical and radiographic criteria is essential. Though there can be a role for this procedure as an index surgery, it is not commonly performed as an index surgery in the United States; it is typically used in the revision setting given its invasive nature and risk of serious irreversible articular and subchondral injury to the trochlea (93). Due to trochleoplasty’s limited use and technical complexity, there is a scarcity of studies on return-to-play outcomes in athletes. However, one study in Germany found approximately two-thirds of athletes undergoing trochleoplasty and patellar-stabilizing procedures return to their preoperative level of sports activity or higher, though high-level athletes are less likely to regain full competitive participation. The average time to return to sports was around 10.8 months, with 42% achieving full pre-injury performance levels (94). However, additional research on trochleoplasty is necessary before formal return-to-sport guidelines can be established.

Chondral lesions

In PFI, chondral lesions—damage to the patellofemoral joint’s cartilage—can be a serious complication requiring urgent surgical intervention. These lesions often occur with lateral patellar dislocations, which may lead to osteochondral fractures, where both cartilage and bone fragments become dislodged (38,39). Such injuries worsen PFI and significantly increase the risk of joint degeneration, including patellofemoral osteoarthritis.

Early surgical intervention is crucial when chondral lesions are detected, but particularly for athletes when they are large and there are mechanical symptoms present. Cartilage damage, especially when coupled with recurrent dislocations, can rapidly progress into osteoarthritis if not addressed. Early surgery prevents irreversible joint damage and preserves knee function. When a large osteochondral fragment is present, surgery may be required to fix or remove the fragment and restore joint stability (84,95). Without intervention, loose bodies in the knee joint can cause mechanical symptoms such as pain, locking, and impaired performance, accelerating joint degeneration.

By addressing both the cartilage injury and PFI through procedures like MPFL reconstruction, the risk of complications, including osteoarthritis, is significantly reduced (96,97). For athletes, early detection and treatment are key to preserving knee function and ensuring a safe return to sports.

RTP

Criteria for RTP

RTP after patellar dislocation or surgery for PFI is a multifaceted process aimed at ensuring both functional recovery and injury prevention. A criterion-based rehabilitation approach is widely recommended, focusing on restoring strength, joint stability, proprioception, and neuromuscular control before allowing a full return to sports (2,75). Following nonsurgical treatment, RTP requires complete ROM, quadriceps and hip abductor strength at least 80% of the uninjured leg, and the ability to perform sport-specific movements without pain or instability (65,72). Strengthening key muscles, particularly the quadriceps, gluteus medius, and hip abductors, is critical, as deficiencies in these muscle groups are linked to higher re-injury rates (68).

Functional testing is a crucial aspect of assessing readiness for RTP, with studies emphasizing the importance of single-limb hop tests, lateral step-down tests, the Y-balance test, and depth jumps as objective measures of dynamic knee stability (2,83). Dynamic movement assessments, such as cutting maneuvers, side hops, and single-leg squats, are essential to simulate sport-specific activities and ensure safe movement mechanics before clearance (2,68).

For postoperative rehabilitation, guidelines such as those from the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine (ISAKOS) emphasize progressive strength training, proprioceptive exercises, and gradual reintroduction of sport-specific activities (72). Quadriceps strength is typically assessed using a seated extension machine, while hip abductor strength is tested in a side-lying position to ensure adequate stabilization of the patellofemoral joint (68). Additional motor control assessments, such as the drop jump test, where the athlete lands and jumps as high as possible from a 35-cm box, and the lateral step-down test, assessing controlled descent to 60° of knee flexion, provide further insight into acceleration, deceleration, and knee control (2,68).

Although RTP timelines vary, many athletes return to modified training between 3–6 months, while full competition-level participation may require 6–9 months, particularly after surgical intervention (2,65). However, recovery should be based on functional progress rather than time alone, as patients returning with residual strength deficits or poor neuromuscular control are at greater risk of recurrent dislocation (3). Treatment decisions are primarily guided by the athlete’s individual goals and risk profile; however, the authors suggest the following algorithm as a framework to support the decision-making process (Figure 4). By following evidence-based rehabilitation protocols, clinicians can help optimize outcomes, reduce reinjury risk, and ensure a safe return to sport for athletes recovering from PFI (2,65,67,68,72).

Figure 4 The treatment algorithm for patellar instability. Each abnormality has to be evaluated and surgically corrected when indicated. Regarding TTO, AMZ and distalization can both be performed together when there is concurrent elevated TT-TG distance and patella alta. As the workhorse surgery, MPFL reconstruction is largely performed in conjunction with all the others. AMZ, anteromedialization; CT, computed tomography; MPFL, medial patellofemoral ligament; MRI, magnetic resonance imaging; RTP, return to play; TT-TG, tibial tubercle-trochlear groove; TTO, tibial tubercle osteotomy.

Psychological aspects in RTP

Psychological readiness is a key factor in RTP and should not be overlooked. Studies show that fear of re-injury can significantly hinder an athlete’s ability to regain pre-injury performance levels, even when physical recovery is complete (98,99). This psychological barrier often delays RTP, emphasizing the need for mental conditioning alongside physical rehabilitation (67). Incorporating psychological counseling and readiness assessments into the rehabilitation process can enhance outcomes (72).

Athletes must demonstrate both competence and confidence in sport-specific drills, which are essential for psychological readiness to RTP. The rehabilitation process is often divided into progressive stages, and during the final phase, functional drills become increasingly sport-specific, allowing athletes to transition from controlled independent drills to complex, unpredictable movements that closely simulate competition demands (67,72). These drills should include game-like scenarios, such as sudden changes in direction, sharp cuts, and playing on uneven surfaces, which are critical for mentally and physically preparing athletes for the dynamic nature of their sport (65).

Exposure to high-risk movements in a controlled environment can help desensitize fear responses, improving an athlete’s trust in their knee stability and movement patterns (67). Research on psychological readiness post-injury suggests that targeted interventions, such as mental imagery, cognitive behavioral strategies, and graded exposure to sport-specific tasks, can help athletes regain confidence and facilitate a successful return to high-level performance (98). Additionally, neuromuscular control exercises enhance proprioception and joint stability, reducing reinjury risk and reinforcing positive movement experiences (65). Athletes who engage in progressive, sport-specific training—including reaction-based drills and fatigue-resistant exercises—report higher psychological readiness and lower reinjury anxiety than those who do not (67). Ultimately, a comprehensive RTP program should address both physical and psychological barriers, ensuring that athletes not only recover physically but also regain the confidence needed to return to their pre-injury level of competition (65,67,98).

Conclusions

Managing PFI in athletes requires a comprehensive approach, addressing both the underlying anatomical factors and the functional needs of the patient. Recurrent lateral patellar dislocations are often associated with conditions like patella alta, trochlear dysplasia, and an increased tibial tubercle-trochlear groove (TT-TG) distance. While non-operative treatment, including physical therapy and bracing, can be effective for first-time dislocations, surgical intervention is often necessary for recurrent cases.

MPFL reconstruction is the primary surgical option for restoring patellar stability and preventing further dislocations. However, additional procedures like TTO or trochleoplasty are often needed to correct significant bony abnormalities that contribute to instability, such as patella alta or a high TT-TG distance.

Addressing chondral lesions is also crucial, as cartilage damage from dislocations can lead to long-term complications like patellofemoral osteoarthritis. Early surgical intervention to repair or remove osteochondral fragments, combined with MPFL reconstruction, helps protect the joint and preserve long-term function.

Ultimately, managing PFI requires a multidisciplinary approach, balancing stabilization with a timely return to sports. Whether through non-operative measures or advanced surgical techniques, the goal is to restore function, prevent recurrence, and protect joint health. With proper patient selection, precise surgery, and comprehensive rehabilitation, most athletes can achieve favorable outcomes and return to high-level activity.

Acknowledgments

None.

Footnote

Peer Review File: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-54/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-54/coif). J.H. serves as an unpaid editorial board member of Annals of Joint from July 2024 to December 2026. J.H. reported an AOSSM Young Investigator Grant for an unrelated research study; he is also an Associate Editor for KSSTA. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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