Introduction

Anterior knee pain is a very common complaint among active individual specially adolescents and young adults¹in many of these patients ,trauma and substantial anatomical misalignment are important cause of patellar pain, in this age group^2,3,4,5,6-7 more ever, in another group of patients with anterior knee pain , no predisposing trauma or subluxation can be identified.⁴ In this group, Fulkeran et al identified a population of patients who had lateral patellar tilting in their axial radiograph without marked subluxation and with chronic peripatellar pain.^8-10 Larson and colleagues attributed the pain in this area of patients to tightness of the lateral retinaculum which leads to increased pressure on the lateral surface of the patella in the femoral sulcus .Hence; they introduced the term patellar compression syndrome (pcs).

Biomechanics

The lateral retinaculum is a richly innervated fibrous connective tissue structure located on the lateral side of the knee.^{11; 12} it is composed of two layers, a superficial and deep layer. the superficial layer is composed of oblique fiber from iliotibial band inserting primarily into the lateral border of the patella and interdigitating with longitudinal fiber of the vast us lateralis and patellar tendon,¹³ The deep layer is mainly composed of dense transverse fiber that connect the deeper portion of the fascia lata directly to the lateral patella. Two distinct ligamentae-epicondylopatellar and patello-tibial ligament are located at the superior and inferior border of the deep layer tethering the patella to the lateral epicondyle and anterolateraltibia respectively, ¹¹ through the contribution of the iliotibial band in the formation of the lateral retinaculum. A posterolateral force is exerted on the lateral aspect of the patella as the knee is flexed.¹² this is consistent with the clinical observation that many patients with anterior knee. Pain tolerate prolonged knee flexion poorly ¹¹ furthermore, this posterolateral force is primarily exerted in a posterior direction and therefore release the lateral retinaculum mainly removes a posterior restrain (tilt) on the lateral patella and to a lesser degree, lateral restrain (subluxation) is decreased13 .Accordingly, lateral release corrects patella tilt more than lateral subluxation (Figure 1and 2).^{12, 14}

Figure 1

(Figure-1)- The lateral patellofemoral angle, LineA-A1 passes through the limits of the femoral sulcus and line B-B1, through the limits of the lateral patellar facet. The lateral patellofemoral angle is formed by the lines A-A1 and B-B1. Note that the lateral patellofemoral angle is always situated anterior to (above) line A-A1.

Figure 2

Figure 2 The congruence angle : To measure the congruence angle: Find the highest point of the medial (B)and lateral (C) condyle and the lowest point of the intercondylar sulcus (A).(A clear plastic straight-edge is helpful)The angle BAC, is the sulcus angle .Bisect the sulcus angle to stablish the xero reference line ,AO.Find the lowest point on the articular edge of the patella (D).(A straight edge held parallel to the horizontal axis of the patella helps) Project line AD. The angle DAO is the congruence angle.All values medial to the zero reference line AOare designated as minus and those lateral ,as plus. Mean= -6 Degrees, standard deviation = 11 degrees.

The cause of knee pain in pcs seems to be multifactorial. Primarily, abnormal tightness of the lateral retinaculum leads to increased compressive forces exerted on the patella when the knee is flexed.^3,4 Subcondral irritation and basal cartilage degeneration also contribute to the occurrence of pain; furthermore, clinical data have demonstrated that in some cases of pcs, pain originates from the sensory nerves supplying the lateral retinaculum due to degenerative neuropathy leading to perineural fibrosis with some loss of myelination.¹¹ Fortunately, regardless of the cause of pain, many of these patients respond well to conservative treatment. Many authors have reported positive results in over 80% of their patients.^14-18 On the other hand, when these conservative measures fail, surgical release of the lateral retinaculum can be successful in alleviating the pain asso¬ciated with PCS.^{6, 14, 19, 20, 21, 22, 23} The aim of the present study was to evaluate the results of surgical release of the lateral retinaculum in cases of patellar compression syndrome.

Patients and methods

33 cases of pcs for whom 56 knees were treated by lateral retinacular release; this study was conducted in the arthritis clinic in the department of orthopedics, MGM Medical College, Indore from December 1999 to June 2001. There were 26 females and 7 males the average age at operation was 35 years (ranging 25 to 40 years). 22 of them patients had bilateral release. 5 patients on right side and 7 patients on left side. The average duration of symptoms prior to surgery was one and half years.

Clinical findings

(I) History -Anterior knee pain is exerted by prolonged flexion (as sitting and squatting) was experienced in187 knees (100%), Giving way was experienced in 151 knees (80.74%). Swelling was present in 112 (60%) knees

(II). Examination -physical examination in¬volved the following:-

Soft tissue tenderness: Tenderness over the lat¬eral Para patellar soft tis¬sue was present in 119 knees (64.11%) Lateral retinacular tightness was 187(100%), direct compression over the patella: revealed ten¬derness in 119 (64.11%). The medial patellar glide test ¹⁴ this evaluates the degree of tightness of the lateral retinaculum. It was performed by manu¬ally pushing the patella medially with the knee in extension. Medial transla¬tion of less than one quad-rant is considered abnormal and is consis¬tent with a tight lateral retinaculum. The test was positive in 151 knees (80.74%) The medial apprehension test: ²⁴ this measures knees discomfort and active re¬sistance to medial patel¬lar displacement with the test was positive in 151 knees (80.74%)

(III).Radiological examina¬tion: Imaging can confirm a diagnosis of patellar malalignments while further qua¬lifying and quantifying it. Standing anteroposterior and lateral views of the knee were obtained to check for signs of articular damage, patella alta and baja, and other associated condi¬tions.^25,26 More importantly, axial tangential views of the pa¬tellofemoral joint, as pro-posed by Merchant, were obtained for each patient to evaluate patellar align¬ment.²⁷ The Merchant radiograph has emerged as the standard, as it allows for proper imaging of patellar articulation with the trochlea.²⁵ Also, it does not artificially compress the pa¬tella as do radiographs made with the patient prone.²⁷ The radiographs were ob¬tained with the knees flexed 45 degrees with the X-ray tube tilted 30 degrees from the horizontal; with the quadriceps muscle relaxed in order not to reduce an existing tilt or subluxa¬tion(figure 3, 4).²⁷

Figure 3

Figure 3 Case no-101merchant view Grade 1 ELPS

Figure 4

Figure 4 Case no-117 Merchant view Grade 2 ELPS

Two measures of patellar malalignment were assessed on the axial radio-graph, namely medial-lat¬eral displacement^25,26i and patellar tilt.^28,29 These two parameters are independent of each other. ²⁵ Lateral displacement (subluxation) was measured with use of the congruence angle²⁷(Table-1) This angle is formed by a line that bisects the sulcus angle and another line which is projected from the apex of the sulcus angle through the lowest point on the articular ridge of the patella.

Figure 5

Table-1 X ray findings Merchant view (specific measurement)

In the normal knee, the congruence angle is usually negative if it opened medially or was parallel. ^14,25,29 In this study, the diagno¬sis of the patellar compres¬sion syndrome (PCS) was made when the clinical set¬ting consisted of complaints of anterior knee pain with no predominant instability, clinical signs pointing to lat¬eral retinacular tightness, and radiological evidence of lateral patellar tilt with minimal subluxation. Patients fulfilling those criteria were subjected to a comprehensive medical program consisting of progres¬sive isometric quadriceps Strengthtellar tip lies medial to the bisector) with a mean value of - 6 degrees. Any lateral deviation of the angle of more than +16 degrees de-notes subluxation.1'l5 Patellar tilt was mea¬sured using the lateral pa¬tellofemoral angle.^{25, 29} This is the angle formed between the lateral facet of the patel¬la (drawn as a straight line joining the lateral and infer¬ior ridges of the patella) and a line joining the highest points on the medial and lateral femoral condyles. The lateral femoral condyles. The lateral patellofemoral angle was considered normal if it opened lateral abnormal opening exercises, re¬striction of activities that require more than 90 de¬grees of knee flexion, peri¬odic administration of anti-inflammatory agents, and a program aiming at maintain¬ing improved muscle troph¬ism^{16, 17} If noncooperative management for a minimum of 3 months has failed, lat¬eral retinacular release was indicated.l4>Q ANGLE: is increased in 19 knees (10%).

Technique of surgery

The procedure was per-formed under tourniquet control. Diagnostic arthro¬scopy of the knee joint was routinely done before the release, to confirm the clin¬ical impression of patellar malalignment; to rule out associated meniscal, syno¬vial, and tibiofemoral patho¬logic conditions; and to evaluate the degree of patel¬lofemoral articular degen¬eration. Next, the miniarthrotomy was done through a 3cm longitudinal incision approximately 2 cm lateral to the patella. The skin and subcutaneous tissues were retracted and the proximally and distally, by blunt dissection. All layers of the retinaculum were incised midway between the lateral border of the patella and the lateral femoral condyle. At the superolateral border of the patella, the fatty plane between the vastus lateralis and vastus lateralis obliquus muscles on the fascial side of the dissection was identified of the vastus lateralis mayo scissors were inserted into the apex of the retinacular incision at this fatty plane and were pushed proximally for about 4-5 cm to comple¬tely divide the lateral retina¬culum (figure5, 6)

Figure 6

Figure 5 Case no.-118 Incision for lateral retinacular release Right knee.

Figure 7

Figure 6 Case no.-118 –Showing lateral retinaculum release Right knee.

This was done cautiously to be certain not to detach the vastus lateralis tendon. The distal portion of the release was then per-formed to the level of the tibial tubercle by incising the retinacular and capsular layers only to avoid injury to the anterior portion of the lateral meniscus. The skin incision was then mobilized proximally or distally to in¬spect all portions of the re-lease site. A successful release was confirmed by the ability to evert the patel¬la 90 degrees. The tourni¬quet was then released and meticulous hemostasis ob¬tained with particular atten¬tion to the lateral superior geniculate vessels which lie close to the vastus lateralis insertion. Postoperatively, a Jones-type compression bandage was used. The involved knee was kept elevated for 48 hours and thereafter weight bearing was encouraged as tolerated by each patient. This was followed by active range of motion exercises with particular concentra¬tion on quadriceps isometric exercises in extension. As soon as peripatellar tender¬ness disappeared, isotonic quadriceps exercises were instituted. Most of the pa¬tients were allowed to return to athletic activity after the sixth postoperative week assessment were done monthly for the first 3 post-operative months and then every 3 months until the final assessment.(Table-2)

Figure 8

Table-2 Efficacy Assessments

The period of follow-up ranged from 12 to 37 months with an aver-age of 17 months.(Table-3)

Figure 9

Table-3 ARA Functional Class

Assessment of results

In our study 56 knees were treated by lateral retinacular release in which 75% knees were given excellent results and 21.48% knees were given good result and 3.75% knees were given fair results, one case of Pcs was treat with Maquet’s procedure that had given excellent result. (Table-4, 5)

Figure 10

Table-4 Patients Global Evaluation of Condition

Figure 11

Table-5 Physician global evaluation of condition

Complications

Mild swelling only after vigorous activity. No extension lag rang of motion 10 degree less than of opposite knee. The patellar compression syndrome: Treatment by miniopen lateral retinacular release.

Radiological findings

Preoperatively, all knees had an abnormal patellar tilt in their axial views as mea¬sured by the lateral patello¬femoral angle. The angle opened medially in 50 knees) and was parallel (zero degrees) in another 6. Following release of the tight retinaculum, the angle was restored back to normal (i.e. opened laterally) in all the knees

Before operation, the mean congruence angle was -5 degrees (range, +35 to -15 degrees) preoperatively com¬pared with -7 degrees (range, +25 to -10 degrees) post-operatively. The average cor¬rection (medialization) was 2degrees (mean 1 degree). However, no significant sta¬tistical association could be detected between the amount of radiological cor¬rection following release and the end result.

Results

According to mention criteria 42 knees (75%) were rated as excellent, 12 knees (21.5%) good ,2 knees(3.57%) fair and 0 knee(0%) poor, For the purpose of statistical analysis, the excellent and good results were grouped as satisfactory and poor results were grouped as unsatisfactory, therefore, a satisfactory result was achieved in 54 knees (96.5%),whereas, the fair and poor results were grouped as unsatisfactory, therefore, a unsatisfactory result was achieved in 2 knees (3.57%)(Table- 4,5)

Discussion

The patellar compression syndrome (PCS) points to a group of symptoms arising from minor abnormalities in the extensor mechanism causing increased pressure over the lateral patellar fa¬cet. ^{4, 14, 21} this pressure is accentuated during flexion, explaining the intensifica¬tion of pain with activities requiring prolonged knee flexion. A review of the literature points to the fact that other terms were also given to this syndrome; thus Ficat and Hungerford`<sup>31</sup> used the term “excessive lateral pressure syndrome,” Johnson11 “lat¬eral facet syndrome of the patella,” LaBrier and O'Neil <sup>22</sup> “patellofemoral pain syndrome” and others<sup>15,16,18</sup> “patellofemor¬al stress syndrome.” <sup>4</sup>, <sup>30, 31</sup> in this syndrome, the lat¬eral retinaculum becomes excessively tight, resulting in lateral tilting of the patel¬la. As knee flexion pro¬gresses, the patella is forced into a congruent reduction in the femoral trochlea, which then stretches the shortened lateral retinaculum. Pain in the lateral retinaculum re¬sults from stretching of this tightened tissue. Further-more, tilting of the patella increases the stresses across the lateral facet, which may eventually lead to cartilage breakdown.<sup>11</sup> Johnson<sup>11</sup> has stressed the importance of thorough history taking and clinical examination for correct diag¬nosis of the syndrome. A complaint of dull achy ante¬rior knee pain exacerbated by prolonged knee flexion (sitting or squatting) or re¬sisted knee extension (as in stair climbing) in a young adult should raise some sus¬picion of the syndrome. If this is combined with posi¬tive physical signs indicating lateral retinacular pathology and positive radiological findings in the axial views, the diagnosis can be made with confidence.<sup>11, 14</sup> in the present study, the presence of well localized tenderness over the lateral retinaculum was highly as¬sociated with a satisfactory result. This is expected be-cause it pinpointed to the tight or degenerative retina¬culum as the source of the problem and hence a satis¬factory outcome following surgical release. Abnormal lateral retinacular tightness was measured by the medial patellar glide test. The pre¬sence of a positive test was correlated with a correct di¬agnosis of the syndrome and hence a satisfactory end re¬sult. In addition, apprehen¬sion to passive medial patellar displacement proved to be a significantly prognostic test. Arthroscopic evidence of articular degeneration of the lateral patellar facet cor¬related with the end result. None of the knees with se¬vere degeneration (Outer-bridge grades III and IV) attained a satisfactory re¬sult. Conversely, 93% of the knees with milder degenera¬tion attained a satisfactory result. Osborne and Ful¬ford<sup>32</sup> showed poor results in all patients with Outer-bridge grades III and IV after lateral retinacular re-lease. Ogilvie-Harris and Jackson<sup>33</sup> noted good re¬sults in 85% of a group of patients with Outer bridge grade I and II compared with only 65% in those with more significant articular degen¬eration. The explanation for these findings might be that as articular cartilage break-down becomes manifest in PCS, collapse in the lateral facet occurs. Hence, lateral release may fail to restore the patella to normal align¬ment because the patella and femoral trochlea are no long¬er congruent.' 10i the primary objective of lateral release is to reduce the compressive and tilting forces imposed on the patel¬la. This can be done either by endoscopic or open techni¬ques. The miniopen proce¬dure followed in this study produced a satisfactory re¬sult in over 84% of the cases. This matches with the satis¬factory results reported by O'Neilf 21 (88%), Metcalf<sup>34</sup>, (86%), Betz <sup>35 (</sup>83%), Dzio¬ba`³⁶ (83%) and Larson et a^l4 (82%). On the other hand, Gecha and Torg²³ reported only 57% satisfac¬tory results and attributed this to the inclusion of cases with overt subluxation in their series. They conse¬quently cautioned against performing retinacular re lease in cases with marked subluxation or disloca¬tion. ²³ The complication rate in this study was very low. The most significant complica¬tion was medial subluxation of the patella that occurred in a single knee. This iatro¬genic mishap happens when the tendon of the vastus lateralis is mistakenly in¬cluded in the release. ³⁷ Therefore, intraoperatively, the fatty plane between the vastus lateralis and vastus lateralis obliquus muscles should be clearly identified and only the obliquus slip should be released. A review of the literature points to haemarthroses as the most common complication of lat¬eral release.^{11, 14, 21, and 23.35}However, the total preva¬lence of haemarthroses after open release was reported to be much lower than after arthroscopic techniques in which the incidence of haemarthroses was over 10 % in some series.^34,38 some authors have even did surgery by arthroscope and no significant differences in outcome between arthroscopic and open lateral release could be documented.³⁹ It is note-worthy that before conduct¬ing the present series, a pilot study was performed to com¬pare open and arthroscopic techniques of retinacular release. The study included three endoscopic cases, two of which developed post-operative haemarthroses. Consequently, the arthro¬scopic technique was aban¬doned in favor of the miniopen method. Further-more, the absence of post-operative haemarthroses in the present series may be attributed to the fact that in each case the tourniquet was released before closure to accomplish meticulous hemostasis with special attention to lateral superior geniculate vessels. A capsular release caused a further reduction in medial stability has been documented recently.⁴⁰

Conclusion

Miniopen re tinacular release proved to be a simple and effective method for treating patients suffering from the patellar compression syndrome. It combines the advantages of satisfactory exposure of the release field, thorough hemostasis and at the same time leaves a very small scar. Arthroscopic examina¬tion of the joint should always be included in the procedure, and if advanced arthritic changes are en-countered, release should better be avoided.