Carl H. Wierks and Andrew J. Cosgarea
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, or overuse. It also may be caused by lateral compression of the patella on the femur.
The patella is guided through its normal course in the trochlea of the femur by the static soft tissue as well as the dynamic muscular stabilizers.11
The lateral retinaculum and patellofemoral ligament make up the lateral static soft tissue stabilizers and can lead to painful compression between the patella and femur if excessively tight.
This scenario has been described as excessive lateral pressure syndrome (ELPS),7 patellar compression syndrome,11 and patellofemoral stress syndrome.14
This chapter describes the surgical treatment of ELPS.
ANATOMY
The patella acts as a fulcrum and provides a smooth surface on which the extensor mechanism can function.5
The thickest articular cartilage in the body is located in the patellofemoral joint.
Forces across the patellofemoral joint are about three times body weight during ascending and descending stairs and can reach up to 20 times body weight during activities such as jumping.3
As the knee flexes from a fully extended position, 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.
In early flexion, the lateral trochlear ridge is the primary restraint.
A tight lateral retinaculum and patellofemoral ligament are responsible for constricting the patella in ELPS.
PATHOGENESIS
An abnormally tight lateral retinaculum can cause pressure and subsequent pain and degeneration of articular cartilage on the lateral aspect of the patella as it encounters the femoral condyle.
Some conditions, such as a weak vastus medialis obliquus, malalignment (abnormal Q angle), internal tibial torsion, and femoral anteversion predispose to lateral tracking.
Other conditions, such as direct trauma (eg, dashboard injury) and dislocation, can result in degeneration of the lateral patellofemoral articular cartilage.
NATURAL HISTORY
No good long-term natural history studies of ELPS have been reported to date.
It is well known, 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 experienced trauma in the past.
Pain typically is exacerbated by prolonged sitting and stair climbing.
Symptoms and clinical findings of instability do not play a part 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 (J-sign)
Patellar tilt test. If the lateral facet cannot be tilted to neutral, the lateral retinaculum is abnormally tight.
Patellar glide test. A lateral glide of up to two quadrants is normal. More than this may indicate excessive lateral translation. Comparison should be made to the normal extremity.
Patellar apprehension test. Apprehension suggests an unstable patella.
Examination for quadriceps tightness, which often is associated with patellofemoral pain.
Patellar grind test. Pain may indicate patellofemoral athritis but also may be found in normal articular surfaces.
Inspection for bony knee malalignment (Q angle)
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs of the knee should include anteroposterior, tunnel, Merchant (sunrise), and 30-degree lateral views. If arthritis is suspected, a posteroanterior flexed 45-degree view should be obtained.
Lateral subluxation can be measured on the Merchant radiograph. If the line through the patellar apex is lateral to a line bisecting the trochlear sulcus angle, then the patella is subluxed laterally (FIG 1A).
A CT scan is the best way to evaluate patellar tilt radiographically. Using an axial image, a line is drawn parallel to the posterior femoral condyles and is compared to a line along the lateral patellar facet. If these lines converge laterally, then the patella has excessive lateral tilt (FIG 1B).
An MRI may be beneficial in evaluating the integrity of articular cartilage and also may show concominant meniscal and ligamentous pathology (FIG 1C).
DIFFERENTIAL DIAGNOSIS
Patellofemoral pain (without excessive lateral pressure syndrome)
Patellar instability
Lateral meniscal tear
Patellar fracture
FIG 1 • A. Merchant radiograph of right knee showing measurement of lateral patellar subluxation. B. Axial CT image of a right knee demonstrating how to measure patellar tilt. C. Axial MRI scan of the right knee of a patient with excessive lateral pressure syndrome.
Iliotibial band syndrome
Prepatellar bursitis
Neuroma
Osteochondritis dissecans of the patella or trochlea
NONOPERATIVE MANAGEMENT
The mainstay of treatment is nonoperative, with most patients benefiting from quadriceps stretching and selective strengthening exercises.
Oral analgesics and bracing also can be beneficial.
Corticosteroid injection or viscosupplementation may be helpful in patients with concomitant 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.8
Lateral release usually is not a successful treatment for lateral patellar instability and, in some cases, can result in iatrogenic medial patellar instabilty.
Successful lateral retinacular release can be performed using either arthroscopic or open techniques.
Preoperative Planning
Range of motion, patellar tilt and subluxation, and ligamentous stability should be examined while the patient is under anesthesthia.
Particular attention should be paid to patellar tracking as the knee is taken through a range of motion (ROM).
The operative knee should be compared to the contralateral side.
Positioning
The patient is placed in the supine position with the operative leg supported according to the surgeon's preference for standard knee arthoscopy (FIG 2).
A nonsterile tourniquet is placed around the thigh.
Approach
A superolateral inflow portal is established just lateral to the vastus lateralis obliquus.
Standard inferomedial and inferolateral portals are used.
FIG 2 • Patient positioning for standard knee arthroscopy using a leg holder and superolateral portal.
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 intra-articular pathology.
The posteromedial and posterolateral compartments are visualized using the Gillquist technique.
Meniscal tears, articular cartilage lesions, and loose bodies are identified and addressed sugically when indicated.
Patellofemoral tracking is visualized as the knee is put through its ROM.
Once the diagnostic arthroscopy is completed, an Esmarch bandage is used to exsanguinate the leg, and the tourniquet is inflated.
The camera is placed in the inferomedial portal and a hooked coagulation device in the inferolateral portal.
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 electrocaudery device (TECH FIG 1B).
The release should extend down to the level of the inferolateral portal.
Great care should be taken to not cut the vastus lateralis muscle or tendon.
If the superior lateral geniculate vessels are seen, they should be aggressively coagulated.
Patellar tilt is assesed after release. The surgeon should be able to tilt the patella 30 to 45 degrees with the knee fully extended.
Excessive lateral release may result in medial instability.
After the release is completed, the tourniquet is gradually deflated to assess for excessive bleeding.
The portal sites are closed, and a sterile compression dressing and cryotherapy device are applied.
Use of a drain may be considered on a case-by-case basis.
TECH FIG 1 • A. The proximal starting point for lateral retinacular release is just distal to the superolateral inflow cannula. B. Arthroscopic view demonstrating successful release of the capsule and tight lateral retinaculum.
POSTOPERATIVE CARE
A compression dressing and a cryotherapy device are used to decrease risk of hemarthrosis.
Patients are allowed to progress to weight bearing as tolerated and discard crutches when they are ambulating safely.
Patients are initially seen 1 week after surgery to assess knee motion and quadriceps function and to remove sutures.
Some patients benefit from formal physical therapy for ROM and quadriceps strengthening to facilitate ruturn to normal function.
OUTCOMES
Arthroscopic isolated lateral retinacular release has a success rate ranging from 70% to 93%.12,13,15
One prospective, randomized study13 found that 93% of patients returned to presymptomatic activity level.
The same study found quadriceps strength deficits in 40% of patients, but in almost all cases the strength was within 10% of the normal leg.13
Arthroscopic and open techniques have similar success rates.5,11–13,15
Success rates of lateral release are lower when performed for instability alone4,6,9 or when advanced patellofemoral arthritis is present.1,17
COMPLICATIONS
Hemarthrosis is the most common complication, followed by infection.10
Medial instability from overaggressive release can be especially difficult to manage. The diagnosis of medial instability can be difficult to make. Patients may report a sensation of lateral instability if the patella sits in a medially subluxed position during early flexion, then snaps laterally during continued flexion. This is important because if the clinician incorrectly treats the presumed lateral instability with a medial stabilization procedure, the symptoms could worsen.16
Other potential complications include quadriceps tendon rupture, patella baja, thermal injury, and arthrofibrosis.10
REFERENCES
1. Aderinto J, Cobb AG. Lateral release for patellofemoral arthritis. Arthroscopy 2002;18:399–403.
2. Aglietti P, Insall JN, Cerulli G. Patellar pain and incongruence. I: Measurements of incongruence. Clin Orthop Rel Res 1983;176: 217–224.
3. Aglietti P, Menchetti PPM. Biomechanics of the patellofemoral joint. In: Scuderi GR, ed. The Patella. New York: Springer-Verlag, 1995:25–48.
4. Betz RR, Magill JT III, Lonergan RP. The percutaneous lateral retinacular release. Am J Sports Med 1987;15:477–482.
5. Ceder LC, Larson RL. Z-plasty lateral retinacular release for the treamtent of patellar compression syndrome. Clin Orthop Rel Res 1979;144:110–113.
6. Christensen F, Soballe K, Snerum L. Treatment of chondromalacia patellae by lateral retinacular release of the patella. Clin Orthop Rel Res 1988;234:145–147.
7. Ficat P. The syndrome of lateral hyperpressure of the patella. Acta Orthop Belg 1978;44:65–76.
8. Fithian DC, Paxton EW, Post WR, et al. Lateral retinacular release: a survey of the International Patellofemoral Study Group. Arthroscopy 2004;20:463–468.
9. Kolowich PA, Paulos LE, Rosenberg TD, et al. Lateral release of the patella: indications and contraindications. Am J Sports Med 1990; 18:359.
10. Kunkle KL, Malek MM. Complications and pitfalls in lateral retinacular release. In: Malek MM, ed. Knee Surgery: Complications, Pitfalls and Salvage. New York: Springer-Verlag, 2001:161–170.
11. Larson RL, Cabaud HE, Slocum DB, et al. The patellar compression syndrome: surgical treatment by lateral retinacular release. Clin Orthop Rel Res 1978;134:158–167.
12. McGinty JB, McCarthy JC. Endoscopoic lateral retinacular release. A preliminary report. Clin Orthop Rel Res 1981;158:120–125.
13. O'Neill DB. Open lateral reinacular lengthening compared with arthroscopic release. J Bone Joint Surg Am 1997;79A:1759–1769.
14. O'Neill DB, Micheli LJ, Warner JP. Patellofemoral stress. A prospective analysis of exercise treatment in adolescents and adults. Am J Sports Med 1992;20:151–156.
15. Panni AS, Tartarone M, Patricola A, et al. Long-term results of lateral retinacular release. Arthroscopy 2005;21:526–531.
16. Post WR. Anterior knee pain: diagnosis and treatment. J Am Acad Orthop Surg 2005;13:534–543.
17. Shea KP, Fulkerson JP. Preoperative computed tomography scanning and arthroscopy in predicting outcome after lateral retinacular release. Arthroscopy 1992;8:327–334.