DEFINITION

Patellofemoral pain is a common symptom in active adolescents and adults.

The diagnosis of patellofemoral pain is nonspecific. It may be caused by trauma, instability, overuse, or anatomic abnormalities such as bipartite patella, maltracking, or malalignment. It may also be caused by a tight lateral retinaculum causing excessive compression of the patella on the lateral femoral trochlea.

The patella acts to enhance the extensor mechanism of the knee as it glides through its normal course within the femoral trochlea. Static bone and soft tissue stabilizers as well as dynamic muscular stabilizers

maintain the patella within the femoral sulcus.18

The lateral retinaculum and patellofemoral ligament make up the lateral static soft tissue stabilizers of the patella. If these structures are abnormally tight, the patella can be excessively compressed against the femur with knee flexion, causing pain.18

This scenario of exaggerated patellar compression on the lateral femoral trochlea has been described as excessive lateral pressure syndrome (ELPS),10 patellar compression syndrome,18 and patellofemoral stress syndrome.25

This chapter describes lateral retinacular release of the knee, which is the surgical treatment for patients with ELPS who exhibit patellofemoral pain, a tight lateral retinaculum, and lateral patellar tilt. This surgical intervention is indicated for patients with ELPS only after nonoperative treatment has failed.

Lateral retinacular release has also been used to treat other patellofemoral disorders with varying success, including chondromalacia patellae, patella malalignment, and instability.2,4,8,15,20,21,22,29 In this chapter, we will focus our discussion on ELPS, the most widely accepted indication for knee lateral

retinacular release.

 

ANATOMY

 

The patella is a sesamoid bone that acts as a fulcrum in knee extension, providing a smooth surface over which the extensor mechanism can function while protecting the anterior knee.7

 

 

The patella also acts to centralize the converging forces of the four quadriceps muscles. The thickest articular cartilage in the body is located in the patellofemoral joint.

 

Forces across the patellofemoral joint are approximately three times the body weight during ascending and descending stairs and can reach up to 20 times the body weight during activities such as jumping.1

 

As the knee flexes from full extension, the patella is drawn into the trochlear groove at approximately 20 degrees.

 

In extension, the medial patellofemoral ligament is the primary restraint to excessive lateral translation. As the knee flexes beyond 20 degrees, the lateral trochlear ridge becomes the primary restraint.

 

A tight lateral retinaculum and patellofemoral ligament may be responsible for excessively constricting the patella and causing symptoms of knee pain in patients with ELPS.

 

PATHOGENESIS

 

An abnormally tight lateral retinaculum can tether the patella against the lateral femoral trochlear during knee flexion, at which point patients may describe a sensation of pressure, grating, or symptoms of pain. With chronic excessive pressure, degeneration of articular cartilage in the lateral patellofemoral joint can occur.

 

Some conditions, such as a weak vastus medialis obliquus normal alignment (abnormal Q angle, lateralized tibial tuberosity, valgus deformity, internal tibial torsion, and femoral anteversion), predispose to lateral patellar tracking.

 

Direct trauma (eg, dashboard injury or patellar dislocation) can also result in degeneration of the lateral patellofemoral articular cartilage.

 

NATURAL HISTORY

 

No long-term natural history studies of ELPS have been reported to date.

 

It is well accepted, however, that disruption of articular cartilage results in progressive degenerative changes.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients typically report insidious onset of anterior knee pain that is activity related, although some may have a history of traumatic injury.

 

 

Pain is typically exacerbated by prolonged sitting, stairclimbing, or an increase in activity. Symptoms and clinical findings of instability have no role in ELPS.

 

A thorough physical examination should include the following:

 

 

Examination for effusion. Effusion may indicate traumatic or degenerative disruption of the articular surface.

 

Observation of patellar tracking. A positive J sign, indicating patellar maltracking, occurs if the patella sits laterally in extension, then suddenly glides medially as it engages in the trochlear with flexion.

 

Patellar tilt test. The examiner attempts to lift the lateral border of the patella. If the lateral facet cannot be elevated to neutral, the lateral retinaculum is abnormally tight.

 

 

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Patellar glide test. Patellar lateral glide of up to two to three quadrants is normal. Excessive lateral translation indicates incompetence of the medial retinaculum and the medial patellofemoral ligament. Comparison should be made to the contralateral leg.

 

Patellar apprehension test. As with the patellar glide test, examiner pushes the patella laterally. If the patient is apprehensive, it suggests that he or she is sensing patellar instability.

 

Examination of the quadriceps. Quadriceps tightness has been associated with patellofemoral pain. Quadriceps weakness, especially involving the vastus medialis, indicates a predisposition to instability.

 

Patellar grind test. With the knee in full extension, the examiner pushes directly down onto the patella, compressing it against the femoral sulcus. Pain may indicate patellofemoral arthritis but can also occur with normal articular surfaces.

 

Inspection for elevated Q angle. The Q angle is measured with the patient in a supine position as the angle formed by a line from the anterior superior iliac spine to the center of patella and a line from the center of the patella to the tibial tubercle. An angle of more than 15 to 20 degrees is abnormal and can predispose to lateral patellar subluxation.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Radiographs of the knee should include anteroposterior, tunnel, axial (sunrise), and 30-degree lateral views. If arthritis is suspected, a posteroanterior flexed 45-degree view should be obtained.

 

 

 

 

FIG 1 • A. Axial radiograph of a right knee showing lateral subluxation of the patella, as the line from the patellar apex to the trochlear sulcus is lateral to the line bisecting the trochlear sulcus angle. B. Axial computed tomography image of the right knee showing measurement of patellar tilt. A line (A) is drawn across the posterior femoral condyles, and a parallel line (B) is drawn and placed at the lateral trochlear ridge. A third line (C) is drawn along the lateral patellar facet. Radiographic confirmation of an excessively tight lateral retinaculum is demonstrated if lines B and C converge laterally. C. An axial magnetic resonance imaging of the right knee of a patient with ELPS, illustrating changes associated with chondral damage.

 

 

Lateral subluxation can be measured on the axial radiograph. If a line drawn from the patellar apex to the center of the trochlear sulcus is lateral to a line bisecting the trochlear sulcus angle, then the patella is subluxed laterally (FIG 1A). A computed tomography scan is the best way to evaluate patellar tilt radiographically. Using an axial image, a line is drawn along the posterior femoral condyles. This line is then compared to a line drawn along the lateral patellar facet. If these lines converge laterally, then the patella is determined to have excessive lateral tilt (FIG 1B).

 

A computed tomography scan can also be used to measure the tibial tubercle-trochlear groove (TT-TG) distance.

 

Magnetic resonance imaging may be beneficial in evaluating the integrity of articular cartilage and may also

reveal concomitant meniscal and ligamentous pathology (FIG 1C).

 

DIFFERENTIAL DIAGNOSIS

 

 

Patellofemoral pain (without ELPS) Patellar instability

 

 

 

 

 

Lateral meniscal tear Patellar fracture Iliotibial band syndrome Prepatellar bursitis Neuroma

 

 

Osteochondritis dissecans of the patella or trochlea Bipartite patella

 

 

 

Patellofemoral arthritis Medial patellar plicae6

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NONOPERATIVE MANAGEMENT

 

The mainstay of treatment is nonoperative, with the great majority of patients seeing improvement in patellofemoral knee pain after quadriceps stretching, strengthening, and physical therapy.12,16

 

Oral analgesics can be beneficial for a limited period of time.

 

Corticosteroid injection or viscosupplementation may be helpful in patients with concomitant chondral degeneration or arthritis.

 

SURGICAL MANAGEMENT

 

The indication for lateral retinacular release is failure of an adequate trial of rehabilitation in a patient with symptomatic patellofemoral pain, excessive lateral retinacular tightness, and lateral tilt.11 Before consideration for surgery, physical therapy should be attempted and deemed unsuccessful.27

 

Isolated lateral release is usually not a successful treatment strategy for lateral patellar instability and, in some cases, can result in iatrogenic medial patellar instability. In patients undergoing a tibial tuberosity osteotomy,

the addition of lateral retinacular release may improve overall results.9 Successful lateral retinacular release can be performed using arthroscopic or open techniques.

 

Preoperative Planning

 

Knee range of motion, retinacular tightness, and ligamentous laxity should be examined while the patient is under anesthesia.

 

Particular attention should be paid to patellar tracking as the knee is taken through a range of motion and whether the patella is dislocatable.

 

The symptomatic knee should be compared to the contralateral side.

 

 

 

FIG 2 • Patient positioning for standard knee arthroscopy using a leg holder.

 

Positioning

 

The patient is placed in the supine position with the operative leg supported according to the surgeon's preference for standard knee arthroscopy (FIG 2).

 

A nonsterile tourniquet is placed around the thigh.

 

Approach

 

For arthroscopic lateral release, a superolateral inflow portal is established just proximal to the superior pole of the patella and lateral to the vastus lateralis obliquus. Standard inferomedial and inferolateral arthroscopy portals are used.

 

TECHNIQUES

 

• Arthroscopic Lateral Release

   

   

  Diagnostic arthroscopy is performed with the 30-degree arthroscope placed in the anterolateral portal. The entire knee is examined to rule out concomitant intraarticular pathology.

   

  The posteromedial and posterolateral compartments are visualized by passing the arthroscope through the intercondylar notch.

   

  Meniscal tears, articular cartilage lesions, and loose bodies are identified and addressed surgically when indicated.

   

  Patellofemoral tracking is visualized as the knee is taken through its full range of motion.

   

  Once the diagnostic arthroscopy is completed, an Esmarch bandage can be used to exsanguinate the leg if the surgeon chooses to use a tourniquet.

   

  The camera is placed in the inferomedial portal, and a hooked coagulation device is placed in the inferolateral portal. Other techniques have been described using the holmium:YAG laser or hook knife.5

   

  Under direct arthroscopic visualization, the release is started just distal to the inflow cannula (TECH FIG 1A).

   

  First, the synovium is cut, exposing the underlying retinaculum.

   

  The retinaculum, which has a distinct firm feel, is then cut using multiple passes with the electrocautery device (TECH FIG 1B).

   

  The release should extend distally to the level of the inferolateral portal.

   

  Great care should be taken to avoid cutting the vastus lateralis muscle or tendon (TECH FIG 1C).

   

  If the superior lateral geniculate vessels are seen (TECH FIG 1D), they should be aggressively coagulated. The ability to coagulate these vessels immediately upon encountering them is one advantage of using electrocautery devices for this step.

   

  Patellar tilt is assessed after release. The surgeon should be able to tilt the patella approximately 30 degrees laterally with the knee fully extended.

   

  Excessive lateral release, which may result in medial patellar instability, must be avoided.

   

  If a tourniquet was used, it is gradually deflated after completion of the release to evaluate for excessive bleeding under direct visualization.

   

  The portal sites are closed, and a sterile compression dressing along with a cryotherapy device are applied.

   

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  TECH FIG 1 • A. The proximal starting point for the lateral retinacular release is just distal to the superolateral inflow cannula. B. The synovium is cut first, revealing the retinaculum. C. The retinaculum is cut using multiple passes of the electrocautery. D. Here, the superior lateral geniculate artery can be seen.

• Open Lateral Retinacular Release

   

  A skin incision approximately 3 cm long is made just lateral to the patella.

   

  The retinaculum is incised in line with the skin incision, approximately 2 cm lateral to the lateral patellar margin.

   

  The superior lateral geniculate artery should be identified and cauterized.

   

  The proximal and distal extent of the incision is adequate when the patella can be laterally elevated to an adequate angle from the epicondylar axis.26

   

  Excessive release should be avoided in order to decrease the risk of iatrogenic medial instability, which has led some surgeons recommending performing a lateral retinacular lengthening.

• Lateral Retinacular Lengthening

   

  After making the longitudinal skin incision lateral to the patella, the lateral retinaculum is incised superficially in line with the skin incision, approximately 1 cm lateral to the lateral patellar border (TECH FIG 2A). The deep fibers of the retinaculum in close contact with the joint capsule are not cut.

   

  A flap of retinaculum is then created by dissecting laterally in this plane approximately 2 cm.

   

  An incision is then made through the deep fibers of the retinaculum and the superficial capsule, leaving a thin layer of capsule intact (TECH FIG 2B).

   

   

  The deep incision is continued proximally and distally until the patella can be everted adequately. The superior lateral geniculate artery should be identified and coagulated.

   

  The free edge of the medial capsule with deep retinacular fibers and the free edge of the superficial lateral retinaculum are sutured together with the knee flexed (TECH FIG 2C).

   

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  TECH FIG 2 • A. The open retinacular lengthening is done through a lateral parapatellar incision. B. The superficial lateral retinaculum is incised longitudinally lateral to the patella, whereas the deep lateral retinaculum and the joint capsule are incised approximately 2 cm lateral to the first incision. C. The free edges of the deep retinaculum/capsule and the superficial retinaculum are sutured together to effect lengthening.

   

  PEARLS AND PITFALLS

   

  Indications

• The indication for isolated lateral release is retropatellar pain from the lateral patellofemoral joint secondary to soft tissue tightness but only after nonoperative management has failed. Lateral retinacular release should not be performed as an

  isolated procedure if patellar instability is the primary problem.11,30

   

  Instability ▪ It is important to not transect the vastus lateralis obliquus muscle and tendon during release because doing so can predispose to medial instability.

   

  Hemostasis ▪ The superior lateral geniculate artery is at risk during lateral release (see TECH FIG 1D). If a tourniquet is used in an arthroscopic release, deflating it before closure can help identify excessive bleeding. Use of a cryotherapy device and a compression dressing will also decrease the risk of hemarthrosis. Use of a drain may be considered on a case-by-case basis in any of the arthroscopic or open approaches.

   

  Landmarks guiding length of release

• The superolateral inflow cannula is an excellent guide for the most proximal starting point of release. The release should extend distally to the inferolateral portal.

 

 

 

POSTOPERATIVE CARE

 

A compression dressing and a cryotherapy device are used to decrease the risk of hemarthrosis.

 

Patients are allowed to progress to weight bearing as tolerated and discard crutches when they are ambulating safely.

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Patients are initially seen 1 week after surgery to assess knee motion and quadriceps function and to remove sutures.

 

Time spent strengthening the quadriceps and hamstrings has been shown to directly correlate with results.23

OUTCOMES

Arthroscopic and open techniques have similar success rates.7,18,20,24,27 Success rates range from 70% to 93%.19,20,24,27

Arthroscopic release may result in less postoperative incisional pain and better cosmesis than open

techniques.

One study found that lateral lengthening had better clinical outcomes, less medial instability, and less quadriceps atrophy at 2 years than open lateral release.26

One prospective, randomized study24 found that 93% of patients returned to presymptomatic activity level and, although 40% of patients had quadriceps strength deficits, in almost all cases, the strength was within 10% of that of the normal leg.

The success rates of lateral release are lower when it is performed for instability alone.3,8,16

 

 

 

 

COMPLICATIONS

There is no significant difference in postoperative complications (hemarthrosis, infection, need for reoperation) when comparing open versus arthroscopic techniques,19 and hemarthrosis is the most common complication followed by infection.13,17

Medial instability from overaggressive release can be especially difficult to diagnose.

Patients may report a sensation of lateral instability if the patella sits in a medially subluxed position during early flexion and then snaps laterally during continued flexion.

If a patient with medial instability is initially misdiagnosed with lateral instability, surgical treatment with a medial stabilization procedure could result in exacerbating the problem.28

An open lateral closure procedure can be used to treat medial patellar instability that results after lateral retinacular release.14

Other potential complications include quadriceps tendon weakness or rupture, patella baja, thermal injury/subcutaneous burns, arthrofibrosis,17 paradoxical increased lateral patellar instability, anterior knee pain, reflex sympathetic dystrophy,14 synovial herniation, or recurrence of ELPS.26

 

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18. Larson RL, Cabaud HE, Slocum DB, et al. The patellar compression syndrome: surgical treatment by lateral retinacular release. Clin Orthop Relat Res 1978;(134):158-167.

     

     

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24. O'Neill DB. Open lateral retinacular lengthening compared with arthroscopic release. A prospective, randomized outcome study. J Bone Joint Surg Am 1997;79:1759-1769.

     

     

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26. Pagenstert G, Wolf N, Bachmann M, et al. Open lateral patellar retinacular lengthening versus open retinacular release in lateral patellar hypercompression syndrome: a prospective double-blinded comparative study on complications and outcome. Arthroscopy 2012;28: 788-797.

     

     

27. Panni AS, Tartarone M, Patricola A, et al. Long-term results of lateral retinacular release. Arthroscopy 2005;21:526-531.

     

     

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