Lateral retinacular release (LRR) was first described by Merchant and Mercer in 19741Merchant A.C. Mercer R.L. Lateral release of the patella: A preliminary report. for treatment of parapatellar pain and patellar instability. It was initially perceived to be a simple, low-morbidity procedure, and its indications were expanded to include various forms of knee pain and patellar instability. Since then, many authors have recognized and reported on the deleterious effects of an unindicated or overzealous LRR. Hughston and Deese published the first report of iatrogenic medial instability after LRR.2Z-plasty lateral retinacular release for the treatment of patellar compression syndrome. Besides medial patellar instability, other reported complications of LRR include quadriceps weakness, quadriceps atrophy, lateral patellar instability, and disabling pain.As the role of the lateral retinaculum in patellar stabilization was increasingly recognized, lateral retinacular lengthening (LRL) was proposed as an alternative to LRR.2Z-plasty lateral retinacular release for the treatment of patellar compression syndrome. The advantages of LRL over LRR include controlled elongation of lateral retinaculum, maintenance of vastus lateralis/quadriceps tendon integrity and avoidance of lateral void, synovial herniation and joint swelling. The indications for LRL include lateral patellar hypercompression syndrome and as an adjunct to surgical procedures performed to address patellar instability. The lateral retinaculum is considered to be tight if the patellar tilt is 20° or more on axial imaging with the knee in extension and if it cannot be passively corrected to a neutral position3Dejour H. Walch G. Nove-Josserand L. Guier C. Factors of patellar instability: An anatomic radiographic study. (Fig 1).

Fig 1Illustration of excessive lateral patellar tilt greater than 20˚ with reference to the posterior femoral condyles.

The anatomy of the lateral retinaculum has been widely studied. Despite some variations in terminology and the reported structures comprising the lateral retinaculum, the 2-layered arrangement of the retinaculum is accepted. The superficial oblique retinacular fibers receive contribution from the fascia of the vastus lateralis. The deep transverse retinacular fibers are composed of the lateral patellofemoral ligament and receive contribution from the iliotibial band. The plane between these 2 layers facilitates a coronal plane Z-plasty lengthening of the lateral retinaculum.

Surgical TechniqueThe surgery (Video 1) is performed under general anesthesia with regional nerve block. The patient is positioned supine on a radiolucent table. An examination under anesthesia is performed with the knee in extension to evaluate for patellar subluxation in medial and lateral directions and to evaluate the extent of passive correction of lateral patellar tilt (Table 1). If the medial subluxation is 1 quadrant or less, and if the patella cannot be everted up to a neutral position (Fig 1), then the lateral retinaculum is considered to be tight.

Table 1LRL Technical Keys, Pearls and Pitfalls

The tourniquet is inflated, and the knee is flexed about 45° over a triangle or bolster (Table 1). A 5-6 cm longitudinal skin incision is placed on the anterior aspect of the knee (Video 1). If both medial and lateral-sided surgery are planned, the incision is placed in the midline (Fig 2) (Video 1); otherwise, the incision is placed just lateral to the lateral border of the patella. Subcutaneous flaps are created, and the lateral retinaculum is identified (Fig 2).

Fig 2Midline approach to the right anterior knee with patient in supine position and planned lateral retinacular incision, with emphasis on avoiding proximal extension into the vastus lateralis tendon.

A longitudinal parapatellar retinacular incision is made about 8-10 mm lateral to the lateral border of the patella (Fig 2). The proximal-distal extent of the incision is from the superolateral aspect of the patella to its inferolateral aspect; care is taken to avoid transection of the vastus lateralis tendon proximally (Fig 2). The incision can be extended distally toward the Gerdy tubercle and farther along the lateral border of the patellar tendon if a concomitant distal stabilization procedure (e.g., tibial tubercle osteotomy) is planned. The depth of the incision is controlled to cut only the superficial oblique fibers of the lateral retinaculum (Fig 3) (Fig 4) (Video 1). Sharp dissection is then performed posteriorly (laterally) between the superficial oblique fibers and the deep transverse fibers of the lateral retinaculum (Fig 3) (Fig 4) (Video 1). The plane between the 2 retinacular layers is best defined along the midpatella, where the retinaculum is dense and thicker (Table 1) (Video 1), before becoming tenuous at its proximal and distal extent.4Anatomy of the lateral retinaculum of the knee. Once about 1.5-2 cm of posterior dissection has been performed, a second longitudinal incision is made through the deep transverse retinacular fibers, and synovial layer (Fig 3) (Fig 5). The arthrotomy is completed, and the knee is extended to assess for any intra-articular lesions (Fig 5). Arthrotomy is not always required. Care is taken to avoid lateral superior genicular vessels at the proximal extent of the dissection.

Fig 3Illustration of 30˚ lateral patellar tilt superficial oblique fibers (blue) and deep transverse fibers (yellow) for coronal Z-lengthening step-cut (dotted black).

Fig 4Patient's right knee, in supine position. Development of the fascial plane between incised superficial oblique (blue) and intact deep transverse fibers (yellow).

Fig 5Patient's right knee, in supine position. Longitudinal incision through the deep transverse fibers (yellow) and capsular layer (white) completing the Z-incision. The lateral femoral condyle is visible in this example.

With the knee flexed 45° (Table 1), the 2 free edges of the retinaculum should lie at the desired length when at rest. The free posterior edge of the superficial retinaculum is tentatively sutured to the anterior free edge of the deep retinaculum/capsule using a few interrupted 0-Vicryl sutures (Fig 6), allowing for a coronal plane Z-plasty elongation of the lateral retinaculum (Fig 6) (Video 1). The amount of lateral retinacular length achieved is generally 1.5-2 cm, though it could range from 1-3 cm, depending on the amount of posterior dissection between the 2 retinacular layers (Fig 6). The knee is extended and the adequacy of the LRL is confirmed by the ability to evert the patella to about 30° past neutral (Fig 7) and achieve 1-2 quadrants of medial patellar translation (Fig 8) (Table 1). The lateral retinacular length can be adjusted as needed by imbricating the 2 free edges of the retinaculum. Once satisfied with amount of LRL, the repair between the 2 free retinacular edges is reinforced by using interrupted 0-Vicryl sutures (Fig 6) (Video 1). Subcutaneous tissues are closed using 2-0 Vicryl sutures, and subcuticular closure is performed using 4-0 Monocryl sutures. Steri-strips are applied, followed by standard dressing.

Fig 6Illustration of neutral patellar position after lengthening the lateral retinaculum with provisional suturing.

Fig 7Illustration of 30˚ (maximum) medial patellar tilt after repair, verifying the adequacy of lengthening and provisional repair.

Fig 8Illustration of acceptable 1-2 quadrants of medial patellar subluxation after retinacular lengthening.

The postoperative course is dictated by the concomitant procedures performed along with LRL. For isolated LRL, no knee immobilization or weight-bearing restrictions are applied. Active and passive range of motion and static quadriceps exercises are initiated in physical therapy in the first postoperative week. After pain and swelling have been controlled, resistive quadriceps exercises are initiated. The patient is released to full activities approximately 3 months postoperatively.

DiscussionIn a prospective double-blinded study comparing the complications and outcomes of open LRR and LRL in the treatment of lateral patellar hypercompression syndrome, LRL demonstrated less medial instability, less quadriceps atrophy and improved clinical outcomes at 2 years when compared with LRR.5Pagenstert 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.,6Is it lateral retinacular lengthening versus lateral retinacular release or over-release?. In another randomized controlled study comparing arthroscopic LRR and LRL in patients with anterior knee pain and patellar tilt, patients with LRL had significantly better knee scores, were more likely to return to previous levels of athletic activity and demonstrated better quadriceps strength on isokinetic dynamometer testing.7Open lateral retinacular lengthening compared with arthroscopic release: A prospective, randomized outcome study. In both studies, however, the LRR was considered complete only when the lateral border of the patella could be rotated 90° anteriorly, with the patella standing on its medial edge; this extent of LRR would be an over-release and should be discouraged.Isolated lateral-sided procedures should not be performed when treating patellar instability.8Fithian D.C. Paxton E.W. Post W.R. Panni A.S. Lateral retinacular release: A survey of the international patellofemoral study group. If the patellar tilt is >20° on axial imaging (CT scan or magnetic resonance imaging) with the knee in extension and cannot be passively corrected to the neutral (0°) position, then LRL should be considered as an adjunct to other stabilizing procedures, including medial patellofemoral ligament reconstruction or tibial tubercle osteotomy.9Levy B.J. Jimenez A.E. Fitzsimmons K.P. Pace J.L. Medial patellofemoral ligament reconstruction and lateral retinacular lengthening in the skeletally immature patient. During trochleoplasty, LRL may be used as an approach to access the dysplastic trochlea.10Trochleoplasty, medial patellofemoral ligament reconstruction, and open lateral lengthening for patellar instability in the setting of high-grade trochlear dysplasia. During quadricepsplasty for a complex patellar instability pattern, wide lateral releases are necessary. LRL during such procedures would prevent a large lateral void and synovial herniation and would provide a passive restraint to patellar eversion from medial over-pull of the transposed quadriceps mechanism. Additionally, a competent lateral retinaculum has been confirmed in biomechanical studies to prevent lateral patellar instability.11Cancienne J.M. Christian D.R. Redondo M.L. et al.The biomechanical effects of limited lateral retinacular and capsular release on lateral patellar translation at various flexion angles in cadaveric specimens. Besides patellar instability, LRL would be indicated for patellofemoral pain secondary to lateral patellar hypercompression syndrome that is refractory to conservative treatment.5Pagenstert 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.Although LRR can also be performed without a formal arthrotomy of the joint by keeping the synovial layer intact and cutting the capsular layer, LRL as an alternative offers several advantages (Table 2). The advantages of LRL include controlled lengthening that maintains the continuity of the vastus lateralis (thereby decreasing quadriceps weakness and atrophy and allowing faster rehabilitation), prevention of iatrogenic medial instability, prevention of excessive swelling, and avoidance of egress of synovial fluid in the subcutaneous tissues. The potential complications of LRL include cosmesis, recurrence of a tight lateral retinaculum resulting from the scarring of tissues, injury to the superior or inferior lateral genicular arteries, saphenous neuroma, and wound-healing issues.2Z-plasty lateral retinacular release for the treatment of patellar compression syndrome.

Table 2LRL: Advantages and Disadvantages