Return to Play Considerations After Patellar Instability

Abstract

Purpose of Review

To discuss the treatment options and rehabilitation protocols after non-operative and operative treatment of patellar instability, and to discuss expected return to play outcomes and functional performance with non-operative and operative treatment of patellar instability.

Recent Findings

A criterion-based program assessing range of motion, joint effusion, strength, neuromuscular control, proprioception, agility, and power are critical measures to assess when rehabilitating this population. A series of functional tests including quadriceps strength testing, single-limb hop testing, lateral step-down test, the side hop test, the lateral leap and catch test, the Y-balance test, and the depth jump should be considered when determining an athlete’s return to sport clearance. These objective measures combined with psychological readiness and a comprehensive understanding of the sports-specific tasks required for participation should be considered when evaluating an athlete’s ability to safely and successfully return to sport.

Summary

We discuss rehabilitation management when working with non-operative and operative management of patellar instability and provide considerations for clinicians working with these athletes to facilitate safe return to sport.

Introduction

Patellar instability can be a challenging injury to manage, particularly when working with athletes wishing to return to sport. Patellar dislocations primarily occur in the lateral direction and can occur during non-contact play, where the athlete’s foot is planted with a dynamic valgus and external rotation stress at the knee [1–3]. Fifty to 60% of first-time lateral patellar dislocations occur from sports-related activity. Soccer, basketball, football, and gymnastics have been identified as the highest-risk sports for this injury [1–3].

Patellar dislocations occur more frequently in the skeletally immature athletic population, with individuals under the age of 20 years demonstrating the greatest risk. Anatomic risk factors such as ligamentous laxity, tibial torsion, increased femoral anteversion, patella alta, trochlear dysplasia, increased Q-angle or lateralized of the tibial tuberosity, and genu valgum, can contribute to increased risk of injury [4]. Taller adolescent females also appear to have an increased risk of instability when compared to their peers [1].

The medial patellofemoral complex (MPFC) has been described as the primary static stabilizer of the patella against lateral translation [5, 6]. The MPFC is comprised of the medial patellofemoral ligament (MPFL) and the medial quadriceps tendon femoral ligament (MQTFL). The MPFC provides static restraint against lateral patellar translation between 0 and 30 to 70⁰ of knee flexion [6, 7] and is often injured after lateral patellar dislocation.

Risk factors associated with higher rates of recurrent instability have been identified as female sex, younger patients particularly those under 16 years of age, bilateral instability, patella alta, trochlear dysplasia, and an increased tibial tuberosity to trochlear groove (TT-TG) distance. Individuals with multiple risk factors can have a high risk of recurrence, and therefore clinicians working with patients with multiple risk factors should articulate the individual’s respective risk in detail and may consider having a lower threshold for surgical intervention [8•, 9, 10].

Non-operative Treatment

Primary patellar dislocations have often been treated conservatively in the absence of a displaced osteochondral fracture or loose body. More recent studies have highlighted the role of risk stratification to determine treatment options after a first-time patellar dislocation [4, 11]. Conservative management is the preferred primary course of treatment for individuals with an isolated patellar dislocation without high risk of recurrence. A short period of immobilization from two to six weeks can aid in symptom management. The duration of immobilization is determined based on the severity of the injury, presence of concomitant injuries, and the resolution of acute symptoms. During this period of immobilization, quadriceps muscle re-education exercises are performed to combat atrophy and inhibition [12]. Exercises maintaining the knee in full extension are appropriate at this stage in conjunction with neuromuscular electric stimulation to increase quadriceps activation.

Once the acute inflammation subsides, the individual can gradually increase activity. Emphasis on controlling effusion, establishing normal gait mechanics, restoring pain-free range of motion, regaining strength, and improving function are pillars to this methodical progression. The use of a lateral buttress brace can be helpful for individuals as functional activities progress [13] and may be indicated when the athlete returns to play [12, 14]. However, there is a lack of well-defined controlled studies supporting this use of these braces [15–17].

Gentle patella mobilization should be performed with caution and only in the presence of identified patellofemoral hypomobility. Exercise selection should be guided by a thoughtful understanding of the arthrokinematics of the patellofemoral joint. Closed kinetic chain (CKC) exercises from 0 to 50° of flexion and open kinetic chain (OKC) exercises from 50 to 90° of flexion have been shown to demonstrate less patellofemoral joint reaction forces. Closed kinetic chain exercises in flexion angles greater than 85° and OKC exercises from 0 to 60° generate significantly greater compressive forces on the joint. Therefore, CKC greater than 50° of knee flexion should be introduced with caution as well as OKC exercises within 0–60° due to increased joint compressive stress [18–20].

Therapeutic exercises reestablishing dynamic quadriceps control as well as targeting activation of gluteal muscles and trunk stabilizers should be prioritized as pain and inflammation subside. Neuromuscular control exercises aiming to decrease dynamic valgus, femoral internal rotation, contralateral hip drop, ipsilateral trunk lean, and other aberrant movement patterns should also be achieved before higher level impact activities are considered.

A gradual return to running program should not begin until 70–80% of quadriceps limb symmetry index (LSI) has been achieved and monitoring adverse signs of joint stress should continue throughout the course of therapy. Double limb and single limb plyometrics should be included at this stage, followed by change in direction, agility, and other conditioning drills. Periodic testing should continue until the athlete has achieved 90–95% on their quadriceps LSI and the individual passes the battery of return to sport tests described later in this article before returning to sport.

The ultimate goal of conservative management is to prevent subsequent dislocation. If the individual reports any subsequent episodes of patellofemoral instability during the course of rehabilitation, surgical intervention should be reconsidered. Of note, recurrent episodes of instability are associated with a 70–86% incidence of chondral injury [21, 22]. The consequence of a chondral injury on a younger patient can have devastating implications on their long-term outcomes and ability to participate in sport.

Conservative treatment for first-time dislocation may lead to a subsequent dislocation with a reported recurrence rate of 14–66% [23, 24]. Many patients with first-time dislocations do not return to their prior level of competition. Atkin et al. [25] performed a prospective study on individuals who had an acute first-time lateral patellar dislocation. Seventy-four participants averaging 19.9 years underwent “standardized rehabilitation” emphasizing range of motion, muscle strength, and return to function. Individuals were cleared to return to sport when they had achieved full passive motion, no joint effusion, and a quadriceps limb-symmetry index of 80% compared to the unaffected side. At 6 months, 58% of participants reported persistent limitation with strenuous sports-specific activity [25]. It is important to consider that this study did not perform any other functional movement tests to determine readiness for return to sport.

Surgical Treatment

Patients with recurrent patellar dislocations, or first-time dislocations with high risk for recurrence, may undergo surgical stabilization. Surgical technique is tailored to the patient’s specific pathoanatomy, and therefore can vary widely between cases. MPFC reconstruction is performed to reconstitute the static restraint to lateral patellar translation. Given the variability of the attachment of the MPFC, multiple surgical techniques have been described, including fixation of the graft on the patella (MPFL reconstruction), quadriceps tendon (MQTFL reconstruction), or both (combined MPFL and MQTFL reconstruction) [26•, 27•, 28•, 29, 30, 31]. Each technique has been reported to have good clinical outcomes [26•, 27•, 28•, 29, 30, 31].

In addition to MPFC reconstruction, the additional factors that can contribute to patellar instability should be assessed and addressed as needed. Assessment of tuberosity lateralization can be performed radiographically using measurements such as tibial tubercle to trochlear groove (TTTG) distance and tibial tubercle to PCL (TTPCL) distances [32–34]. TTTG distances greater than 20 mm have been associated with failure to fully recreate the kinematics of the patellofemoral joint with MPFL reconstruction alone, in a cadaveric study [35]. Medializing or anteromedializing tibial tubercle osteotomy (TTO) can be performed to correct this malalignment, although the exact indication and benefit remain to be determined [36, 37]. TTO can also be used to address patella alta, although distalization should be performed with caution, given the higher risk of complications [38]. Greater rotational and/or coronal plane malalignment can be addressed with tibial or femoral osteotomies as needed. While the indications for trochleoplasty are evolving, this can be performed when there is considerable prominence of a convex trochlea or supratrochlear spur, such as when this prevents the engagement of the patella with within the trochlear groove.

In rehabilitation after patellar stabilization surgery, it is paramount to confirm the procedure and guidelines at the onset of treatment, as multiple variations of surgical treatment options exist and can vary by the patient and/or surgeon. Weightbearing protocols depend on the addition of, and type of, concurrent bony procedures performed and often require longer durations of protected weightbearing than patients undergoing MPFC reconstruction alone. For isolated MPFC reconstructions, a period of protected weightbearing for up to 6 weeks is recommended. During the first 2 weeks, toe touch weightbearing with the brace locked in extension is appropriate to help protect healing structures. After 2 weeks, the individual can begin weightbearing as tolerated and unlock the brace when the quadriceps strength improves, demonstrated by the ability to perform an independent straight leg raise without a quadriceps lag and resume normal gait mechanics without a quadriceps avoidance gait pattern.

Typically, early rehabilitation after isolated MPFC reconstruction follows similar guidelines to non-operative treatment. An emphasis on decreasing effusion and postoperative pain is facilitated through the use of compressive garments and ice. Surgeons will often advise a gradual increase in knee flexion over the first 6 weeks. Progression to full weightbearing is typically recommended soon after surgery with the postoperative brace locked in full extension during ambulation, unless the patient has undergone additional bony procedures. Quadriceps muscle re-education exercises are performed to combat atrophy and inhibition and use of neuromuscular electric stimulation is encouraged [12]. Exercises maintaining the knee in full extension are appropriate at this stage. Many guidelines will delay some aspects of the rehabilitation timeline by 4–6 weeks in the setting of osteotomy, to allow for bony healing prior to progression.

As the athlete progresses through each phase of rehabilitation, it is important to develop adequate strength and neuromuscular control in the quadriceps, hamstrings, and gluteal muscles. Single-leg exercises developing eccentric control and proximal stability should be prioritized. The athlete is expected to demonstrate good eccentric control with a single-leg squat including appropriate depth, without dynamic valgus at the knee, femoral internal rotation, contralateral hip drop, or ipsilateral trunk lean. In order to begin impact activities, the individual must demonstrate trace to no effusion, full, symmetrical knee range of motion, and quadriceps LSI of > 80% [39•].

When the athlete has successfully met these criteria, they are cleared to begin the walk-to-jog program guided by the physical therapist. This typically occurs around the 12–16-week timeframe but may be delayed due to concomitant procedures such as TTO. It is critical for clincians to be aware of any chondral lesions associated with the athlete’s original injury and consider a slower overall progression and a more sensitive barometer for joint effusion [40, 41]. Athletes with a concomitant TTO or tibial/femoral osteotomy will be slower to progress due to prolonged periods of restricted weightbearing and delayed return of quadriceps strength. Some studies have reported longer RTS timelines with a concomitant TTO, therefore that should be communicated to the athlete and a consideration when establishing RTP timeframes [40, 41].

Functional Testing and Return to Sport

Minimal evidence exists to clearly delineate the functional tests and RTS tests that should be conducted after MPFC reconstruction. Inconsistencies amongst rehabilitation protocols combined with variations in surgical technique contribute to the lack of consensus in the field of sports medicine [42•]. A recent systematic review showed that in a review of 39 articles over the last 20 years, only 16 showed any specific criteria for RTS after patellofemoral surgery [43•]. When RTS tests were conducted, no studies provided the requisite numerical values necessary to RTS. Coda et al. [44•] analyzed 38 publicly available protocols for patellofemoral surgery and only 34.2% included specific criteria for strength or functional testing to RTS [44•]. As a consequence of poorly established return-to-play guidelines, athletes may be returning to sport with impairments and functional limitations that may increase their risk for injury or ability to return to their prior level of competition [41, 45].

Ample evidence exists detailing the RTS guidelines for athletes returning to sport after anterior cruciate ligament (ACL) reconstruction. Many parallels exist between ACL injuries and patellofemoral instability including injury mechanisms, proprioceptive deficits, and neuromuscular impairments postoperatively. Therefore, it has been suggested that the strategies implemented for RTS testing after ACL reconstruction can be used as a valid and reliable testing standard for patellofemoral surgeries.

Strength Testing

A battery of tests including strength, neuromuscular control, and balance can provide insight regarding the athlete’s readiness to return to sport. After MPFC reconstruction, quadriceps strength has demonstrated deficits at 6 months to 3 years postoperatively with a concomitant procedure such as a TTO associated with longer recovery times [40, 43•]. Criteria for RTS to after ACLR is typically > 90–95% [46]. While there is limited evidence to suggest the relationship between isokinetic strength and the rate of reinjury after MPFC reconstruction, strength testing can provide a better understanding into persistent deficits that can help guide treatment.

While isokinetic testing is often considered the “gold standard” for strength testing the quadriceps, many clinics do not have access to this testing equipment due to space and cost [47]. As a result, many clinicians do not have the ability to collect quantitative data when evaluating an individual’s return to sport readiness. Fortunately, hand-held dynamometry has been shown to be both valid and reliable measure of strength. Quadriceps strength can be measured in a seated-leg extension machine with the hips at 90° of flexion and knees at 60° flexion (Fig. 1). The athlete is asked to slowly extend their limb against the fixed lever of the machine and perform a maximal effort against the device. The individual has one practice trial followed by 3 recorded trials. The average is calculated for each limb and the LSI is determined. Both the absolute values given the individual’s age, gender, and activity level coupled with the deficiency compared to the non-surgical limb can guide treatment plans. This test can also be performed to measure hamstrings LSI in a prone position with the hip at 0° of flexion and the knee at 60° of flexion. The same protocol practice and trial protocol is used, and the LSI is calculated.

Fig. 1.

Quadriceps Limb Symmetry Index. Quadriceps strength can be measured in a seated-leg extension machine with the hips at 90° of flexion and knees at 60° flexion. The athlete is asked to slowly extend their limb against the fixed lever of the machine and perform a maximal effort against a hand-held dynamometer

Due to the mechanism of injury for patellofemoral dislocations involving dynamic knee valgus and hip internal rotation, measuring hip abduction strength deficits can also be valuable. Hip strength deficits have been shown in athletes with patellofemoral dysfunction. Testing for the hip abductors is performed in a side lying position with the testing limb in slight extension. A trial followed by 3 consecutive tests on each side to calculate an LSI. The goal of > 90–95% is recommended as criteria for return to sport [48, 49].

Assessment of Motor Control

While MPFC reconstruction with or without bony procedures can correct anatomic and structural risk factors to improve static stability, it does not address the neuromuscular control or dynamic stability that are implicated in increased risk for reinjury following reconstruction. Hop testing as described by Noyes et al. [50] has proved to be a reliable and valid measure of asymmetries in function. The four tests commonly included are single-leg hop for distance, triple hop for distance, crossover hop for distance, and 6-m timed hop. While the distance traveled provides quantifiable data and percentages to evaluate asymmetry, it is critical to evaluate the quality of the motion along with the total distance hopped. These percentages are helpful, but do not provide insight regarding the quality of the movement. Deficits in load absorption at the hip, knee, or ankle can provide valuable information regarding the athlete’s reinjury risk assessment. Careful examination of the athlete’s take-off and landing strategy should be evaluated and asymmetries in the frontal or sagittal planes recorded. Aberrant movement on the non-surgical limb should also be evaluated and considered when determining return to sport readiness [46]. Poor motor control on the unaffected side should not be accepted as the athlete’s normal.

There are several additional tests to include when assessing quality of movement. The side hop test consists of hopping on one leg between two lines at distance of 40 cm apart as many times as possible in 30 s (Fig. 2). The quality of change in direction, endurance, and the number of hops are evaluated. The drop jump is a test that provided information on the athletes preferred landing strategy (Fig. 3). In this test, the patient drops off of a 35-cm-high box, lands on both feet, and immediately jumps as high as possible before a subsequent landing. This gives the clinician information on the individual’s acceleration and deceleration technique. The lateral step-down test and the lateral leap and catch are timed test using a metronome (Fig. 4). The lateral step-down test is performed with the athlete standing on one limb at the edge of a box while performing a lateral step down to 60° of knee flexion. The athlete taps their contralateral heel to the ground and aims to match a cadence of 80 beats per minute (bpm). The test is 3 min in duration and the clinician assesses for loss of balance, significant trunk lean or knee valgus, and inability to match the beat of the metronome. When the athlete demonstrates 3 changes in control, the clinician documents the time. The lateral leap and catch is a 60-s timed test (Fig. 5). The athlete hops lateral from one limb to the other at a distance of 60% of their height. Again, the clinician assesses the overall quality of the motion and the agility to match the beat of the metronome.

Fig. 2.

Thirty-second side hop test. The side hop test consists of hopping on one leg between two lines at distance of 40 cm apart as many times as possible in 30 s

Fig. 3.

Drop jump test. In the drop jump test, the patient drops off of a 35-cm-high box, lands on both feet, and immediately jumps as high as possible before a subsequent landing

Fig. 4.

Lateral step-down test. The lateral step-down test is performed with the athlete standing on one limb at the edge of a box while performing a lateral step down to 60° of knee flexion. The athlete taps their contralateral heel to the ground and aims to match a cadence of 80 beats per minute (bpm)

Fig. 5.

Lateral leap and catch. In the lateral leap and catch, the athlete hops lateral from one limb to the other at a distance of 60% of their height

Dynamic balance should be assessed prior to clearance for RTP. Poor dynamic control has been associated with increased risk for injuries in athletes. The Y-balance test (YBT) is a test that assesses single-leg dynamic stability. The athlete is asked to stand on a platform with toes on a designated line and use the contralateral limb to push a small block as far as possible with sound control and the ability to return to the starting position. The distance in the anterior, mediolateral, and posterolateral positions is recorded and compared to the contralateral limb. The YBT has demonstrated good inter-rater and intra-rater reliability. As little as a 4-cm deficit in forward reach or < 90% composite (includes leg length in its calculation) score has been shown to be a predictor of lower-extremity injury risk [51].

Subjective Measures

Patient-reported outcome measures (PROMs) are important to assess the athlete’s subjective readiness to return to sport. The most common PROMs used after MPFC reconstruction include the IKDC, Lysholm, Tegner, Kujala score, and Banff Patella Instability Index [52]. While these are excellent measures of subjective performance, it is also important to evaluate the athlete’s confidence returning back to sport. Fear of reinjury has been repeatedly reported as a common reason not to return to sport [53].

The anterior cruciate ligament reconstruction return to sport after injury (ACL-RSI) measure is commonly used after ACL reconstruction and has shown predictive value in RTS at 4 months and demonstrates a second injury risk when scoring < 70 [37, 39•]. The Tampa Scale of Kinesiophobia (TSK-11) can also determine an athlete’s fear of movement when returning back to sport. The TSK-11 is an 11-item self-administered questionnaire geared toward quantifying the fear of reinjuries due to movement and physical activity [54]. For ACL and MPFC reconstruction, “fear of reinjury” has been shown to be the primary reason individuals did not return to prior level of play. Parallels can be drawn when considering value of confidence scores with RTS.

Return to sport decision-making should include a battery of tests including a comprehensive assessment of all of objective and subjective measures. A multi-disciplinary approach including collaboration with the surgeon, the physical therapist, the athletic trainer, and the strength and conditioning coaches should be standard care when treating an athletic population. The unique demands of the athlete’s sport should be considered when evaluating return to play readiness.

Comprehensive return to sport testing can begin as early as 4 months after surgery [42•]. Periodic testing is recommended monthly to keep the athlete motivated, revise goals, and tailor the rehabilitation program accordingly. Individuals who do not achieve return to sport clearance at the 6-month mark may require additional care to address the residual deficits impacting their performance. It is important to note that time from surgery alone has repeatedly failed to identify safe return to sport without risk of secondary injury for individuals after ACL reconstruction. Therefore, the use of physiologic healing timelines alone is not recommended for individuals after MPFC reconstruction [55, 56].

Once the athlete passes this series of tests, a progression of sports-specific activities may begin. The athlete can progress from independent sports-specific skills in a controlled setting, to sports-specific drills with varying speed and change in direction, to controlled contact game-like scenarios, to full contact, less predictable game-like play. A gradual increase in endurance, speed, and intensity should be progressed through each phase, introducing various sports-specific scenarios to build the athlete’s confidence and assess for adverse joint reaction or suboptimal movement. If the athlete presents with any increase in symptoms, the individual should remain at that stage until symptoms resolve or regress to the prior phase until the athlete demonstrates normal response to progression.

Some athletes may feel more comfortable returning to sport with some external support but clinicians should be mindful that there is little high-quality evidence to support the use of a patellar stabilizing brace after MPFC reconstruction [15–17]. The use of bracing should not be used to expedite the athlete’s return to sport if the aforementioned criteria have not been achieved.

Conclusion

Clearing an athlete to return to sport after treatment for patellar dislocation can be a complex process that requires a methodical, criterion-based approach to rehabilitation. In working with a diverse pool of athletes with different degrees of skill, and various levels of competition, validated RTP guidelines are necessary to set the standard of care and decrease the athlete’s risk for reinjury. Clinicians should emphasize optimizing the quality of movement while minimizing patellofemoral joint stress. A gradual introduction of sports-specific training should be considered to improve the individual’s confidence to safely return back to prior level of function. A battery of functional tests can aid the clinician when make return to sport decisions and justify further treatment when necessary.

Compliance with Ethical Standards

Conflict of Interest

The authors did not receive any funding or grants in support of the research for or preparation of this work. The authors declare no conflict of interest.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.