Physical Therapy Management of the First-Time Patellar Instability Event

Abstract

Background:

Patellar instability, the subluxation or dislocation of the patella within the patellofemoral joint, is common in adolescents and can significantly affect their function. This study evaluates conservative management for first-time patellar instability events, discussing rehabilitation strategies and criteria for return to activity/sport.

Indications:

Conservative management is typically indicated for patients experiencing a first-time patellar dislocation, particularly when there are no osteochondral injuries or significant anatomic abnormalities.

Technique Description:

Physical therapy management begins with an initial evaluation assessing swelling, core and lower extremity strength, range of motion (ROM), and special tests. This management is divided into 3 phases: acute, intermediate, and late. In the acute phase (0-4 weeks), cryotherapy and compression manage effusion, while early ROM exercises prevent stiffness. The intermediate phase (4-6 weeks) focuses on strengthening dynamic knee stabilizers and incorporating progressive open- and closed-chain exercises. The late phase (6-8 weeks) aims to restore full strength and prepare the patient for return to activity through sports-specific drills and higher-intensity exercises.

Results:

Conservative management for first-time patellar dislocations shows promising outcomes. Early active ROM and strength training are associated with improved knee function, increased ROM, and higher patient satisfaction. Interventions such as patellar taping and nonrigid bracing provide immediate stability and relief, promoting muscle preservation and improved ROM at subsequent follow-ups. Systematic reviews indicate no significant difference in redislocation rates between partial and full weightbearing protocols, supporting the recommendation to avoid immobilization. Key International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) guidelines emphasize complete healing, neuromuscular training, core strength, and psychological readiness for a safe return to sport. Functional assessments like the Y-balance and triple-hop tests help evaluate limb symmetry and functional readiness before resuming activities.

Discussion/Conclusion:

Conservative management is a suitable plan for most first-time patellar dislocations. While there is no single best rehabilitation plan, important principles for management include early ROM and strengthening exercises to promote knee function. Patient evaluation and criteria can help establish a safe timeline for returning to sport, ensuring optimal recovery, and minimizing recurrence risk.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Physical Therapy Management of the First Time Patellar Instability Event, Department of Physical Therapy and Orthopedic Surgery at Virginia Commonwealth University.

The authors have no disclosures pertinent to this presentation.

The objectives of this video are to provide background and epidemiological information on patellar instability, discuss conservative management and rehabilitation techniques for first-time patellar dislocation, and outline criteria for evaluating patients for return to activity or sport.

Background

Patellar instability can be defined as subluxation or dislocation of the patella in the patellofemoral joint. It is more likely in the pediatric population, with an incidence rate of 29 per 100,000 in 10- to 17-year-olds compared to 5.8 per 100,000 in the general population. ¹⁵ Risk factors for patellar instability include acute trauma, anatomic abnormalities such as patella alta or trochlear dysplasia, and hypermobility. ³ Recurrence rates for patellar instability are around 40%, with a greater risk following a repeat patellofemoral joint dislocation compared to a primary patellar dislocation. ⁸

“Gold Standard” for First-Time Dislocator: Nonoperative Management

For most patients with first-time patellar dislocation, conservative management is indicated. ³ Surgical management may be more appropriate in unique situations such as osteochondral injuries with loose bodies or fragmentation that could potentially benefit from early fixation. ³

Indications

Our patient is a 26-year-old woman who presented to her physician with pain in her right knee following a first-time patellar instability event while working her warehouse job. Magnetic resonance imaging revealed transient patellar instability with a bone bruising pattern without anatomic risk factors for recurrence. On physical examination, there is a moderate effusion causing limited knee range of motion (ROM) from 0° to 90° on her affected limb compared to having 5° of hyperextension and 135° of flexion on her contralateral limb. There was also hypermobility of the patella with 2+ quadrant lateral translation. She had positive patellar apprehension and was apprehensive at 45° of flexion on moving apprehension tests. She had decreased activation and ability to fire her vastus medialis obliquus (VMO) and showed signs of arthrogenic muscle inhibition (AMI). Her Beighton score was a 2/9.

Initial evaluation of patellar instability by physical therapy (PT) consists of assessing swelling, strength of core and lower extremity musculature, ROM, and special tests. In addition to evaluating quadriceps strength, other important evaluations include hamstring strength, femoral anteversion, and tibial torsion. ¹⁴

Femoral anteversion is measured by taking the patient's limb into hip internal and external rotation with one hand while using the other hand to palpate the greater trochanter and identify where it is most prominent. Once prominence is found, the examiner will measure the angle of the patient's tibia, with a normal range being 8° to 15° of internal rotation. Biomechanical evidence suggests that a femoral torsion angle of 20° or greater increases risk of patellar instability. ⁵

Tibial torsion is measured with the patient prone and knees flexed to 90°. The examiner is looking at the patient's feet from above and comparing the line of axis of the thigh along the axis of the foot, with the norm being 10° to 15° of external rotation. The examiner can also assess the amount of tibial rotation the subject has by manually rotating the foot internally and externally. In a study of 83 patients with patellar instability, tibial torsion correlated with femoral anteversion. ¹¹

Next, we will discuss the management and rehabilitation considerations of first-time patellar instability.

Technique Description

The management of first-time patellar instability can be divided into 3 phases: acute, intermediate, and late stages.

First, we have the acute phase, which spans the initial 4 weeks. Effusion management consists of techniques like cryotherapy or compression.

Patellar taping may provide patients with an immediate relief of pain and a sense of stability. In a randomized controlled trial of 18 patients with first-time patellar dislocation, patients who received patellar taping preserved more muscle at 6 weeks, had greater ROM at 1 year, and had higher Lysholm scores at 5 years compared to patients who were initially immobilized. ¹²

Furthermore, our recommendation is to avoid immobilization braces and allow for knee ROM. This is supported by a randomized controlled trial of 79 patients demonstrating that non-motion-restricting braces led to greater ROM at 3 months and higher Kujala scores at 6 months. ⁴

There is an emphasis on achieving early, active full ROM as well. A randomized controlled trial of 18 patients demonstrated that, when compared to immobilization, early ROM resulted in improved 4-week outcomes of Kujala scores, knee flexion strength, and composite Y-balance scores. ¹⁰

These are examples of exercises prescribed to restore deficits on ROM. The exercise on the left, known as a heel slide, addresses the patient's flexion, while the stretch pictured on the right is known as a heel prop to promote full hyperextension.

It has been suggested that proximal muscle strength can limit the force exerted on the patellofemoral joint, potentially protecting it from subluxation or dislocation. ⁷ Core exercises, such as Pallof press, rotation, or side plank if tolerable, can promote proximal stability.

Additionally, no restrictions are placed on patients in terms of weightbearing following an instability event. This is supported by a systematic review that found no statistical difference in redislocation rates between partial and full weightbearing, although there was notable heterogeneity among the studied populations. ⁹

AMI is a common deficit that occurs in the quadriceps musculature following trauma to the knee, causing the quadriceps to not activate properly due to neural inhibition. Commonly seen in patellar dislocation populations is the inability to activate the VMO, which, when activated, can assist in preventing lateral patellar dislocations. ¹³ To combat AMI, neuromuscular reeducation can train the patient on how and when to activate their quadriceps. Other helpful tools are techniques such as biofeedback and eStim, which involves electrodes attached to the quadriceps and provides electrical stimulation to assist in activating the neurons in the quadriceps. The goal of addressing AMI should always be to resolve the inhibition of the quadriceps, not just passive ROM.

The intermediate phase lasts from weeks 4 to 6 and involves a continued focus on dynamic knee stabilizer musculature. Furthermore, the goal of this stage should be to address impairments found on evaluation and have the ROM nearly restored.

Patients should progress to open- and closed-chain exercises as ROM is restored, but strength is still lacking. Open-chain exercises can be performed between 50° and 90° of flexion to limit compressive force on the patellofemoral joint. ⁶ An example of an open-chain exercise is a seated knee extension, shown here.

Closed-chain exercises can be performed up to 50° of flexion and then into deeper ranges as the patient can tolerate. ⁶ Examples of closed-chain exercises are a goblet squat, single-leg anterior touchdown, and a lateral stepdown, which all promote quadricep activation and control.

A patient-centered approach is critical to maximize the effectiveness of rehabilitation. For instance, if the patient is struggling with descending stairs, strengthening eccentric quadriceps control and adding cues for proper knee over toes instead of “caving in” could be beneficial.

In the last phase, the focus becomes getting the patient back to the level they desire. For patients aiming to return to sports, sports-specific training can help prepare them for this return and increase safety when returning. ⁸

Examples are cutting and pivoting motions that are common in many sports, along with plyometric exercises like mini hopping with proper movement progressions. Furthermore, this phase may include a higher level of load while strength and ROM are restored. Exercise can be increased over time with full sport activity after 3 months. ²

Results

An important part of managing patellar instability is promoting safe and timely return to activity.

Atkin and colleagues ¹ evaluated 74 patients with first-time patellar dislocation. Criteria used to judge whether patients were ready for return included full passive ROM, no knee effusion, and quadriceps strength at 80% of the uninjured limb. ¹ Most patients recovered ROM at 6 weeks. ¹ At 24 weeks, over 80% of patients achieved the quadriceps strength criteria. ¹

The International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine Consensus Criteria for Return-to-Sport includes complete healing, neuromuscular training, satisfactory core strength, control with dynamic activities, and psychological readiness. ⁸

Assessing strength, stability, and functional performance with key testing exercises is crucial in quantifying a patient's progress. ⁸ The video on the left depicts the Y-balance assessment, which allows for analysis of single-leg balance along with eccentric quadricep control in multiple directions. There should not be greater than a 4-cm difference in the anterior direction or 6 cm in the posteromedial/lateral directions for return to sport and preparticipation screening. The video on the right is a demonstration of the triple-hop test, which is measured for distance and compared between limbs, with an ideal limb symmetry for distance being greater than 90%.

Evaluation for Safe Return to Activity

With regard to return to activity, a Limb Symmetry Index of at least 90% for quadriceps and hip abduction is recommended. ⁶ Isokinetic testing is the “gold standard” for the Limb Symmetry Index, but alternatives such as seated leg extension can also be used. ⁶

Conclusion

In conclusion, conservative management is the protocol for most first-time patellar dislocations. While there is no single best rehabilitation plan, there are many important principles for management and rehabilitation, such as encouraging early ROM and strengthening exercises to promote knee function. Criteria and patient evaluation can help establish a safe timeline for return to sport.

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