关节镜下髌骨支持带调整术联合胫骨结节内移抬高术治疗髌骨外侧半脱位

目的 探讨关节镜下髌骨支持带调整术联合胫骨结节内移抬高术治疗髌骨外侧半脱位的疗效.方法 自2006年3月～2008年1月对16例髌骨外侧半脱位行关节镜下髌骨支持带调整术联合胫骨结节内移抬高术.手术前后采用Lysholm膝关节功能评价表和Tegner下肢运动能力评价表进行评估,并测量手术前后屈膝20°CT片Merchant匹配角、髌骨倾斜角和髌骨外移度.结果 患者获6～28个月随访(平均16个月),术前和术后6个月Lysholm评分分别为(59.00±13.37)分和(92.14±5.15)分(P<0.05),Tegner评分分别为(2.00±1.49)分和(3.30±0.48)分(P<0.05),所有患膝运动能力均较术前有所改善.手术前后Merehant匹配角分别为(21.10±5.61)°和(一1.70±7.41)°(P<0.05),髌骨倾斜角分别为(一4.50±6.45)°和(11.60±2.27)°(P<0.05),髌骨外移度分别为(5.29±3.14)mm和(0.20±1.32)mm(P相似文献   

A modified tibial tubercle osteotomy for patellar maltracking: results at two years

An abnormal lateral position of the tibial tuberosity causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking of the patella causing anterior knee pain or objective patellar instability, characterised by recurrent dislocation. Computer tomography is used for a precise pre-operative assessment of the tibial tubercle-trochlear groove distance. A distance of more than 15 mm is considered to be pathological and an indication for surgery in symptomatic patients. In a prospective study we performed a subtle transfer of the tibial tuberosity according to the information gained from the pre-operative CT scan. This method was applied to two groups of patients, those with painful lateral tracking of the patella, and those with objective patellar instability. We evaluated the clinical results in 30 patients in each group. The outcome was documented at 3, 12 and 24 months using the Lysholm scale, the Kujala score, and a visual analogue pain score. Post-operatively, all but one patient in the instability group who had a patellar dislocation requiring further surgery reported good improvement with no further subluxation or dislocation. All patients in both groups had a marked improvement in pain and functional score. Two patients sustained a tibial fracture six and seven weeks after surgery. One patient suffered a per-operative fracture of the tibial tubercle which later required further fixation. If carefully performed, this type of transfer of the tibial tubercle appears to be a satisfactory technique for the treatment of patients with an increased tibial tubercle-trochlear groove distance and who present with symptoms related to lateral maltracking of the patella.     

Lateral patellar retinaculum tension in patellar instability

The patellar retinaculum is important in patellar tracking. However, little attention has been paid to the biomechanics of the retinaculum. This study assessed the change in tension of the lateral patellofemoral ligament before and after anteromedial tibial tubercle transfer for patellar instability. Twenty-seven knees in 21 patients were studied and the mean age of the patients at surgery was 19 years. A buckle transducer was clamped on the lateral patellofemoral ligament and the transducer was calibrated to zero with the knee at full extension. The knee then was flexed 30 degrees, 60 degrees, 90 degrees, and 120 degrees, and the transducer recorded changes in tension within the lateral patellofemoral ligament. After anteromedial tibial tubercle transfer, lateral patellofemoral ligament tension was measured in the same manner. Although average lateral patellofemoral ligament tension increased with knee flexion with the maximum at 120 degrees flexion, these changes showed four different patterns measuring variability of patellar instability. An increase of lateral patellofemoral ligament tension after anteromedial tibial tubercle transfer meant that lateral retinacular release should be done concurrently to balance patellar tracking. This information may be useful in deciding the appropriate surgical procedure for each patient.     

髌骨半脱位70例治疗分析

目的探讨髌骨半脱位的治疗方法及其预后。方法回顾性分析70例（130膝）髌骨半脱位患者的临床资料,其中男30例,女40例;年龄10～48岁,平均23岁。患者髌骨的形态均为WibergⅡ、Ⅲ型,其中伴有外侧髌股关节骨关节炎者58例108膝,高位髌骨23例46膝,外伤后股四头肌内侧头肌张力不良10例10膝。Q角20°～40°。全部行手术治疗,手术方式包括：髌外侧支持带充分松解（130膝）;髌内侧支持带紧缩、股内侧肌移位至髌骨前内侧（12膝）;髌骨外侧部分切除（17膝）;胫骨结节前、内侧移位（46膝）,平均内移1．0cm、前移1．2cm;缝匠肌前移（11膝）,半腱肌前移（13膝）;关节镜下髌外侧支持带松解,髌内侧支持带紧缩（31膝）。术中见全部病例髌外侧支持带均明显增厚。结果随访3～180个月,根据Insall等评分系统评估分析疗效,术后疗效优78膝,良33膝,可12膝,差7膝。患者术后疼痛、关节活动功能均得到明显改善,尤其是解除膝前痛效果显著。结论根据病因及病理改变选择恰当的手术方式治疗髌骨半脱位均可取得满意的效果,特别是关节镜手术具有创伤小、恢复快的特点,值得进一步推广应用。     

内侧髌股韧带重建联合胫骨结节移位和关节镜下外侧支持带松解术治疗持久性髌骨脱位

目的观察内侧髌股韧带重建联合胫骨结节移位和关节镜下外侧支持带松解术治疗持久性髌骨脱位的效果。方法对6例持久性髌骨脱位患者的10个膝关节行内侧髌股韧带重建联合胫骨结节移位和关节镜下髌骨外侧支持带松解术。手术前后采用Lysholm膝关节功能评价表和Kujala评分表进行评估,并通过CT观测手术前后髌骨外移度。结果 6例均获随访,时间24～36(29±7.21)个月。Lysholm评分术前为47.10分±10.31分,术后24个月为83.11分±5.21分,差异有统计学意义(P<0.05);Kujala评分术前为41.26分±13.36分,术后24个月为82.33分±5.31分,差异有统计学意义(P<0.05)。患膝运动能力均较术前明显改善。髌骨外移度术前为35.61 mm±5.37 mm,术后为4.30mm±1.13mm,差异有统计学意义(P<0.05)。结论内侧髌股韧带重建联合胫骨结节移位和关节镜下髌骨外侧支持带松解术能够有效纠正持久性髌骨外侧脱位,缓解症状,恢复膝关节功能。     

Patellofemoral Pain Disorders: Evaluation and Management

Patellofemoral pain disorders can be difficult to diagnose. Careful attention to the history and physical examination is central to accurate diagnosis. Standardized office radiographs are sufficient in most cases. Computed tomography of the patellofemoral joint (precise midpatellar transverse images through the posterior femoral condyles with the knee at 15, 30, and 45 degrees of knee flexion) will provide valuable objective information regarding subtle abnormalities of patellar alignment. Magnetic resonance imaging and radionuclide scanning may be helpful in selected cases. By differentiating between rotational (tilt) and translational (subluxation) components of patellar malalignment, the clinician will be better able to prescribe appropriate treatment. It is also extremely important to localize and quantitate articular and retinacular abnormalities. While nonoperative treatment is usually successful, surgery is sometimes required. Lateral release will relieve tilt and associated pain in the lateral retinaculum. Realignment of the extensor mechanism, usually at the level of the tibial tubercle, is necessary to control lateral tracking (subluxation) of the patella. If there is lateral or distal medial articular damage related to chronic lateral tilt and/or subluxation, shift of the tibial tubercle will help to unload damaged cartilage while realigning the extensor mechanism.     

Preoperative computed tomography scanning and arthroscopy in predicting outcome after lateral retinacular release.

We initiated a study to look at preoperative, flexed-knee, midpatellar computed tomography (CT) scans and intraoperative arthroscopic findings of lateral patellar articular degeneration in predicting the results after lateral retinacular release for failed nonoperative treatment of anterior knee pain. Twenty patients with 30 painful knees underwent preoperative flexed-knee, midpatellar CT scans that were retrospectively classified by the method of Fulkerson into normal alignment, lateral subluxation, lateral patellar tilt, and combined tilt and subluxation. Arthroscopy was performed before open lateral release. The lateral facet of the patella was graded as either minimal changes (Outerbridge I or II) or advanced (Outerbridge III or IV) changes. Patients were followed for a minimum of 2 years and graded on a standard patellofemoral rating scale. Only 22 of 30 knees that were thought to be clinically malaligned, actually were malaligned by CT scan; eight CT scans were interpreted as normal. The results were further stratified into group A (CT-documented tilt, minimal facet changes), group B (CT-documented tilt, advanced facet changes), and group C (normal CT). Ninety-two percent of group A were rated good or excellent. Twenty-two percent of Group B rated good/excellent, 33% fair, 44% poor. Only 13% of group C rated good (one patient). Based on the results of the study, we recommend lateral release for anterior knee patients with CT-proven patellar tilt who have not responded to conservative treatment and have minimal facet changes with minimal or no subluxation. Lateral retinacular release should not be offered as a treatment to the patient with a normally aligned patella because poor results will most likely result.     

Radiographic and computed tomographic analysis of the position of the tibial tubercle in recurrent dislocation and subluxation of the patella

Among the factors that influence the patellofemoral alignment and stability, the position of the tibial tubercle was evaluated using plain radiographs and computed tomography (CT). Radiographs of the Q-angle with the knee in full extension and quadriceps muscle relaxed showed that mean Q-angles in the dislocation or subluxation group and control group were 13.8 degrees and 14.3 degrees, respectively. The major reason for this deceptive measurement was a patella positioned laterally in the dislocation or subluxation group. Better estimation was made with the modified Q-angle measurement by using the most concave point of the intercondylar notch as a reference point instead of the center of the patella. By overshadowing CT images of the levels of the patellofemoral joint and the tibial tubercle, it was possible to evaluate the location of the tibial tubercle in relation to the femoral trochlea. Both the angular measurement (lateral deviation angle [LDA]) and the distance measurement (lateral deviation index [LDI]) showed that the tibial tubercle in the dislocation or subluxation group was rotated externally and shifted laterally (LDA, 36.3+/-7.0 degrees and LDI, 30.1+/-5.6) compared with the control group (LDA, 20.2+/-7.1 degrees and LDI, 15.1+/-5.6). Further study is warranted to elucidate the exact mechanism of recurrent patellar dislocation and subluxation.     

The management of patella infera in current practice

Patella infera described by Caton et al.The measurement is made in 1982 is an accompanying symptom in certain knee affections secondary to the abnormal situation of the patella. The measurement is made on the X-ray with sagittal view after measuring the patellar height, using the original technique described by the author, when the ratio between the articular surface of the patella and the distance form the patellar tip to the tibial tubercle. Indications of surgery may be when this ration is inferior or equals 0.6. The origin of the patella infera can be mechanical or inflammatory. The operative technique addresses the etiology. In current practice, the patellar height and the patellar tendon length may be evaluated using a sagittal section MRI. In the authors’ experience, when the Caton ratio is lower or equals 0.6 and when the length of the patellar tendon is over 25 mm, the indication of surgery includes proximal transfer of the tibial tubercle. If the length of the patellar tendon is less than 25 mm, it is often necessary to perform a patellar tendon lengthening (PTL). This type of surgery is contraindicated in the authors’ experience in depressive or pusillanimous subjects. The two surgical techniques are described. Both techniques use an anterior and medial approach. The proximal transfer of the tibial tubercle (PTT) includes medial and lateral retinaculum release. The tibial tubercle is detached and transferred upwards according to the pre-operative planning generally 1 or 2 cm and is fixed with 2 screws. PTL includes a medial and lateral retinaculum release often with the fat pad. The patellar tendon is dissociated in the middle over its whole length, and the medial pad is detached of the tibial tubercle and the lateral of the patella. After lengthening, the edges of the tendon are sutured, and this suturing reinforced. Alternative procedures may be used when PTT or PTL are not possible, using transplantation with an allograft of the extensor system or a plasty with hamstring muscles.     

Locked Lateral Patella Dislocation With Generalized Ligamentous Laxity After Arthroscopic Lateral Release of the Knee

We describe the case of a 14-year-old boy with patellar instability on both sides resulting from ligamentous hyperlaxity and dysplasia of the lateral femoral condyle who had previously undergone an arthroscopic lateral release as well as plication of the medial capsule. The patient presented to our clinic 2 years after surgery with a locked lateral patella dislocation on the left side. The surgical correction involved a substantial open lateral release including an excision of the scar tissue and stabilization of the patella in the patellofemoral groove by tibial tubercle medialization and plication of the medial capsule. Six months after surgery, the patient achieved a Lysholm score of 90 points and clinical examination indicated a stable knee with a centralized patella without any evidence of subluxation or dislocation. Open lateral release with partial resection of the lateral retinaculum, medial reconstruction, and tibial tubercle osteotomy was the procedure of choice in this patient with habitual patella dislocation caused by generalized ligamentous laxity.     

Patellofemoral Instability: Evaluation and Management

Patellofemoral disorders are a common cause of knee pain and disability. A thorough history and a careful physical examination are essential to accurate diagnosis, and imaging modalities play an important role. Magnetic resonance imaging can provide information on malalignment and soft-tissue injuries. Although there is a continuum of diagnoses, most patellofemoral disorders can be divided into three distinct categories: soft-tissue abnormalities, patellar instability due to subluxation and dislocation, and patellofemoral arthritis. Many patellofemoral disorders respond to nonoperative therapy. When surgical intervention is necessary, patellar tilt can be successfully treated by a lateral release. Lateral patellar subluxation associated with malalignment can be corrected by a distal realignment procedure such as the anteromedial tibial tubercle transfer. Repair of the medial patellofemoral ligament in cases of patellar dislocation has considerably lowered the incidence of recurrent instability. Although no ideal treatment exists for patellofemoral arthritis, mechanical symptoms may be alleviated by arthroscopic debridement of delamination lesions. Articular cartilage-wear disorders may be stabilized by addressing the primary causative disorder.     

Three-dimensional transfer of the tibial tuberosity for patellar instability with patella alta

Background

Although patellar instability can be treated with several surgical procedures, the appropriate surgical treatment for patellar instability with patella alta has not yet been investigated. The objective of this study is to find out whether three-dimensional transfer of the tibial tuberosity elicits good knee functionality with improved patella alta and prevents further patellar dislocation.

Methods

Twelve knees (10 patients) underwent surgery for patellar instability with patella alta from 2007 to 2011. The surgery performed was a three-dimensional transfer for the anteromedial distalization of the tibial tuberosity. Predisposing anatomical factors for patellar instability were evaluated preoperatively; femorotibial angle (FTA), patella alta (IS ratio), trochlear dysplasia (sulcus angle) and tilting angle (lateral tilt). The function of the knee was assessed before and after surgery by Lysholm and Kujala score.

Results

Before surgery, the IS ratio was 1.34 ± 0.13, lateral tilt was 22.4° ± 6.5°, and the sulcus angle was 151.7° ± 8.3°, indicating patella alta, laterality, and trochlear dysplasia. After surgery, the IS ratio and lateral tilt significantly improved to 0.95 ± 0.13, and 10.6° ± 3.4°, respectively. FTA and sulcus angle were not altered. Lysholm and Kujala score improved from 63.8 to 94.7 and 67.0 to 94.1 points, respectively. Most patients displayed good outcomes except for one patient who suffered re-dislocation by hitting their knee on the floor, 2.5 years after surgery.

Conclusion

Three-dimensional tibial tuberosity transfer was shown to correct the patella position and result in a good clinical outcome. This method is introduced as an alternative surgery for patellar instability with patella alta.     

The unstable patella after total knee arthroplasty: etiology, prevention, and management

In total knee arthroplasty, most complications related to the extensor mechanism are caused by patellar maltracking or instability. Patellar maltracking may result from component malpositioning and limb malalignment, prosthetic design, improper patellar preparation, or soft-tissue imbalance. Patellofemoral instability likely results most frequently from internal malrotation of the femoral or tibial components. Although a patellofemoral radiograph may display the lateral subluxation of the patella, only computed tomography can quantify rotational malalignment of the femoral or tibial component. Nonsurgical treatment is generally unsuccessful; major malposition of components is best managed by implant revision. In the absence of component malposition, proximal realignments (lateral patellar retinacular release with lateral advancement of the vastus medialis obliquus muscle) or tibial tubercle transfers have been used. Surgical procedures on the patellar tendon itself may risk rupture of the extensor mechanism.     

Tibial tubercle transfer: a long-range follow-up study

The prime indications for tibial tubercle transfer are 2 or more complete patellar dislocations with trivial trauma or recurrent subluxation with or without pain causing "giving way." A high "Q" angle, flat lateral condyle, aplastic patella or positive apprehension test may be associated but are not always prime indications in surgery. Methods of fixation are of individual preference in this series and a single screw sufficed. An arthrotomy is not always necessary but is suggested if indicated. If the proximal tibial epiphysis is open, corrective measures are suggested that do not involve the extension of the proximal tibial epiphysis into the tibial tubercle. The tubercle should be advanced to compensate for patella alta and lined up with the femoral shaft. Transplantation of the tubercle medially 3/4' and distally 1/2' was generally satisfactory in a series of 377 operations with an average follow up of 3 1/2 years.     

Tibial tubercle osteotomy in patello-femoral instability and in patellar height abnormality

The aim of this study was to present the different surgical procedures of tibial tubercle osteotomies for patellar instability or patellar mispositioning such as patella alta or patella infera. This study analysed the Caton–Deschamps index used for assessment of vertical patella height in order to make a precise plan for tibial tuberosity osteotomies. This study included 61 knees (50 patients) treated for patellar instability with patella alta and 24 patients treated for patella infera of mechanical origin. The results of medial transfer of the tibial tuberosity, with or without distal transfer in cases of patellar instability with patella alta, gives excellent results for stability in 76.8% of the cases. The results of the proximal transfer of the tibial tuberosity in cases of patella infera were excellent or good in 80% of the cases in our series of 24 patients. A precise preoperative plan is needed with determination of the vertical patellar height using the Caton–Deschamps index and the situation of the tibial tuberosity and the Tibial Tubercle to Trochlear Groove distance (TT-TG) of the knee on CT scan in order to obtain satisfactory results.     

Lateral release rates after total knee arthroplasty.

For a total knee replacement to function well, the patella must track centrally in the trochlear groove. A lateral release may be required to ensure such central tracking. During surgery, an evaluation was made of patellar tracking in 178 patients undergoing total knee replacement. The Genesis II prosthesis with a deep-dish tibial insert was used for all the patients. The evaluation was made using the nontouch technique and the axial traction (modified no-touch) technique before and after release of the tourniquet. With the tourniquet still inflated, there were 29 knees in which the patella tilted laterally and 11 additional knees in which the patella subluxed laterally. Using the modified no-touch technique, there were only 12 knees in which the patella tilted laterally and five in which it subluxed laterally. With the tourniquet deflated, only nine of the patellas tilted laterally and three subluxed laterally. It was only in this final group that a lateral release was done for an overall lateral release rate of 6%. Eleven of these 12 knees had a preoperative fixed valgus deformity greater than 10 degrees. Only one lateral release was required for a patient with a preoperative varus deformity. Four patients with a preoperative fixed valgus deformity and a laterally subluxed patella did not require a lateral release. Axial realignment and reconstitution of an anterior trochlear surface by the implant were sufficient to centralize the patella. Had only the no-touch test been used, there would have been 18 unnecessary lateral releases done. When the knees were evaluated radiographically, there was no statistical difference in patellar position between that group and the knees that required a lateral release. Overall in the entire group at 6 weeks after surgery, 105 knees (59%) had no patellar tilt. At 3 months, as quadriceps tone returned to normal, 138 knees (79%) had no patellar tilt. Thirty-three of the remaining 35 knees had a patellar tilt less than 10 degrees. None of the patients had lateral patellar subluxation at any time after surgery.     

Chronische patellofemorale Instabilit?t

Chronic patellofemoral instability may lead to pain and early osteoarthrosis. Recurrent dislocations of the patella, lateral subluxation and chronic dislocation are summarized under this generic term. There are five different factors which may be responsible of the development of chronic patellofemoral instability: 1) elongation of the medial patellofemoral ligament (MPFL), 2) patella alta, 3) increased distance between tibial tuberosity and trochlea groove (TTTG) distance, 4) trochlea dysplasia and 5) torsional malalignment. To rule out these factors clinical examination, radiological diagnostics (luxation, subluxation in the Defilée view, trochlea morphology, patella alta) and magnetic resonance imaging (MRI) of TTTG distance and trochlea morphology are crucial. The indications of operative treatment are chronic pain with subluxation, chronic dislocation and recurrent dislocation. Currently the former frequently and universally used lateral release is only indicated in cases of subluxation and positive tilt. Biomechanical studies have shown that a lateral release will otherwise increase patellofemoral instability. The choice of the surgical technique depends on the factors underlying patellofemoral instability, the conditions of growth plate and cartilage damage. Among the different surgical options proximal and distal realignment procedures are differentiated. In cases of MPFL elongation and mild passive instability a medial reefing might be successful. In cases of MPFL elongation, high passive instability up to 30° of flexion (with or without trochlear dysplasia) MPFL reconstruction may be the treatment of choice. A trochleoplasty is rarely indicated. This treatment may be considered in cases of high grade trochlea dysplasia and passive instability at more than 30° of flexion. If the TTTG distance is increased (>20 mm) or in cases of patella alta distal realignment with tibial tubercle transfer should be considered. This operation might also be useful in the presence of lateral cartilage damage as an anteromedialization of the patella.     

In vivo movement analysis of the patella using a three-dimensional computer model

We used three-dimensional movement analysis by computer modelling of knee flexion from 0 degrees to 50 degrees in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0 degrees . The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed. The patients had greater values of spin from 20 degrees to 50 degrees , while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0 degrees to 50 degrees , percentage tubercle shift at 0 degrees and 10 degrees and patellar inclination from 0 degrees to 50 degrees with a smaller oval-shaped contact area from 20 degrees to 50 degrees moving downwards on the lateral facet. Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects.     

胫骨结节内移抬高术联合关节镜下髌骨支持带调整术治疗复发性髌骨脱位的疗效研究

目的探讨胫骨结节内移抬高术联合关节镜下髌骨支持带调整术治疗复发性髌骨脱位的疗效。方法自2008年至2012年对12例复发性髌骨脱位行关节镜下髌骨外侧支持带松解、内侧支持带紧缩联合胫骨结节内移抬高术。术后6周、3个月、6个月、12个月、2年、5年进行门诊随访,物理检查包括髌骨内移度检查,髌骨外推恐惧试验,复查轴位X线片了解截骨块愈合情况、髌股关节适合角、髌骨指数,Lysholm膝关节功能评价表、IKDC评分和Kujala评分表进行评估。结果所有患者均获随访,随访时间1~5年,平均2.0年。术后3~6个月复查X线片见截骨块以达到骨性愈合,在负重行走并行膝关节屈伸功能锻炼,膝关节功能恢复良好。术后髌骨内移度均介于1°~2°之间,术后各时间点髌骨外推恐惧试验阳性率、髌骨适合角、髌骨指数与术前比较,差异均有统计学意义（P〈0.05）;术后各时间点间比较,差异均无统计学意义（P〉0.05）。术后6、12个月,IKDC、Lysholm、Kujala评分均较术前显著提高,差异均有统计学意义（P〈0.05）。术后6、12个月IKDC、Lysholm评分比较,差异无统计学意义（P〉0.05）。术后12个月Kujala评分较术后6个月显著提高,差异有统计学意义。结论关节镜下髌骨外侧支持带松解、内侧支持带紧缩联合胫骨结节内移抬高术能够有效治疗复发性髌骨脱位。     

Evaluation of patients with persistent symptoms after lateral retinacular release by kinematic magnetic resonance imaging of the patellofemoral joint

The arthroscopic lateral retinacular release is typically performed to treat patellar pain and instability. This procedure was previously considered to be relatively benign with a low associated complication rate. However, a high incidence of medial subluxation of the patella was recently reported in patients with persistent symptoms after lateral retinacular release. Because the use of physical examination criteria may not always be sufficient to assess patellar alignment, 40 patients (43 knees) were evaluated by the newly developed technique of kinematic magnetic resonance imaging of the patellofemoral joint. One (2%) patellofemoral joint had normal patellar alignment, 10 (23%) had lateral subluxation of the patella, 1 (2%) had excessive lateral pressure syndrome, 27 (63%) had medial subluxation of the patella, and 4 (9%) had lateral-to-medial subluxation of the patella. Seventeen of 40 patients (43%) with unilateral arthroscopic lateral retinacular releases had medially subluxated patellae on the unoperated joints. Because patellar malalignment commonly affects bilateral joints, medial subluxation of the patella may have been present before the lateral retinacular release but was not recognized in these patients.