动态CT观察髌股关节排列异常

目的 分析动态CT评估髌股关节排列的方法 和价值.方法 分别在屈膝0°、10°、20°、30°时用CT检测30例60膝髌股关节,观察膝关节不同屈曲角度髌股关节的排列,测量各屈曲度髌股关节的股骨滑车角、相称角及外侧髌股角,分析不同角度对髌股排列异常的检出率.结果 本组分别在膝关节0°、10°、20°、30°选取髌骨棘与股骨滑车凹最深的层面测量,有15膝的相称角大于16°,为髌骨外侧半脱位,16膝为髌骨外倾,10膝髌骨外侧倾斜合并半脱位.统计学分析证实膝关节屈曲10°和20°对髌骨外倾、半脱位检出率高.结论 动态CT能评估髌股关节排列,膝关节屈曲10°和20°是诊断髌股关节排列异常的重要位置.     

不同翻转角双回波稳态序列MRI评价膝关节骨性关节炎软骨损伤

目的 评估不同翻转角（FA）三维双回波稳态（3D-DESS）序列MRI对评价膝关节骨性关节炎软骨损伤的价值。方法 收集25例单侧膝关节疼痛患者，以FA 30°、60°及90° 3D-DESS序列采集膝关节MRI，评估每例患者髌骨（Pat）、股骨滑车（Tro）、股骨外侧髁（LFC）、股骨内侧髁（MFC）、胫骨外侧平台（LTP）及胫骨内侧平台（MTP）6个软骨情况，根据结果分为软骨损伤阳性（Ⅱ~Ⅳ级）和阴性（0、Ⅰ），对图像评价软骨损伤的诊断信心进行评分。以关节镜检查结果为标准，分析MRI结果与其的一致性。比较不同FA图像的诊断信心评分。结果 对于Pat、Tro、MFC、LFC、MTP、LTP，FA 90° 3D-DESS图像的结果与关节镜结果一致性较好（Kappa＝1.00、0.84、1.00、0.81、0.97、0.91，P均<0.01），但显示正常软骨结构欠佳；FA 60° 3D-DESS图像一致性较好或一般（Kappa＝0.87、0.61、0.81、0.74、0.73、0.68，P均<0.01），周围骨质及软组织显示较好；FA 30° 3D-DESS图像一致性一般或差（Kappa＝0.47、0.38、0.50、0.30、0.32、0.23，P均<0.01），但可清晰显示软骨结构。FA 30°图像诊断信心评分低于FA 60°（P均<0.05）及FA 90°图像（P均<0.01），FA 60°图像诊断信心评分低于FA 90°图像（P均<0.05）。结论 FA 90° 3D-DESS图像显示软骨损伤最佳，FA 30°清晰显示软骨形态及结构，而FA 60°能兼顾周围骨质及软组织，临床中应根据检查目的选择合适的FA。     

DTI评估髌股关节软骨轻度损伤：与关节镜对照

目的 探讨DTI评估髌股关节软骨轻度损伤的价值。方法 回顾性分析82例常规MR诊断髌股关节软骨正常或轻度损伤患者的DTI及关节镜检查资料。根据关节镜检查结果,将其中40例Outerbridge分级Ⅰ、Ⅱ级者纳入髌股关节软骨轻度损伤组,33例无髌股关节软骨损伤者纳入对照组,排除9例Outerbridge分级为Ⅲ、Ⅳ级者。对比分析2组髌股关节软骨DTI表现,并与关节镜结果对照。结果 髌股关节软骨轻度损伤组40例关节镜检查共发现62处软骨轻度损伤;其中通过ADC及伪彩图可显示49处（49/62,79.03%）,FA伪彩图可显示51处（51/62,82.25%）。髌股关节软骨轻度损伤ADC及FA伪彩图表现为软骨色阶不均匀,内见红色或粉色色阶。与对照组正常软骨比较,髌股关节软骨轻度损伤组软骨损伤区ADC值明显增高,FA值明显降低（P均＜0.05）。结论 DTI可显示及量化髌股关节软骨的轻度损伤,为早期软骨损伤的诊治提供有价值的参考信息。     

髌股关节对合关系的CT测量

目的 筛选诊断髌股关节对合异常的CT检查敏感参数.方法 对22例膝前痛患者42侧膝(症状组)及12例无症状者24侧膝(对照组)在屈膝0°、15°、30°、60°时分别对髌股关节行CT扫描,测量每个屈曲角度下的股骨滑车角、外侧髌股角、髌骨倾斜角、和谐角、髌股指数.结果 症状组髌股关节的和谐角、髌股指数明显大于对照组(P<0.01),其余参数无显著性差异(P>0.05).结论 CT扫描是检出髌股关节异常对合的有效方法,其中和谐角、髌股指数对评价髌股关节异常对合更为敏感.     

膝关节术后粘连MRI表现及临床特点

目的 观察膝关节术后关节粘连的MRI征象及其临床特点。方法 回顾性分析27例接受关节镜下膝关节手术后再次经关节镜证实存在膝关节粘连患者,观察其MRI表现及临床特点。结果 膝关节术后关节粘连MRI表现为膝关节腔内不同程度滑膜增厚,T1WI呈低信号,脂肪饱和(FS)质子密度(PD)WI呈中-高信号,其内可见多发条带状T2WI低信号,关节腔内无或仅见少量积液。关节镜及MRI示膝关节术后关节粘连可累及髌上囊(81.48%,22/27)、髌下脂肪垫(77.78%,21/27)、内外侧隐窝(51.85%,14/27)及髁间窝(22.22%,6/27);且多伴(23/27,85.19%)不同程度关节软骨损伤,常累及髌骨软骨及滑车软骨。结论 膝关节术后关节粘连多发生于术后中晚期,好发于髌上囊和髌下脂肪垫,多伴软骨损伤,特别是髌骨软骨和滑车软骨;其MRI特征性表现为不同程度滑膜增厚,FS PDWI呈中-高信号,内见多发条带状T2WI低信号,关节腔内无或仅见少量积液。     

三维稳态进动结构相干序列显示膝关节前外侧韧带

目的 观察三维稳态进动结构相干（3D-CISS）序列显示膝关节前外侧韧带（ALL）的价值。方法 对30名健康志愿者行右侧膝关节MR检查,扫描序列包括轴位和冠状位脂肪抑制质子密度加权（FS-PDWI）及3D-CISS序列。对3D-CISS图像行MPR斜矢状位重建和CPR不同角度冠状位重建,CPR重建角度为0°、30°、60°、90°、120°、150°和180°;观察各序列图像ALL表现,并比较不同序列对ALL股骨部、半月板部、胫骨部、半月板附着点、股骨附着点和胫骨附着点的显示率。结果 3D-CISS序列CPR图像对ALL胫骨附着点和股骨附着点显示率均为96.67%（29/30）,MPR图像均为93.33%（28/30）,均优于FS-PDWI图像（P均<0.017）。3D-CISS序列CPR图像对ALL胫骨部、半月板部和半月板附着点的显示率分别为96.67%（29/30）、83.33%（25/30）和83.33%（25/30）,均高于FS-PDWI图像（P均<0.05）,对ALL股骨部的显示率与FS-PDWI图像差异无统计学意义（P=0.095）。结论 3D-CISS序列联合CPR图像可提高对ALL的显示率。     

30°屈曲位膝关节MRI评价前交叉韧带断裂的价值

目的 探讨30°屈曲体位膝关节MRI对显示前交叉韧带（ACL）和评价ACL断裂的应用价值。方法 选取64例接受膝关节镜检查的膝关节外伤患者,依次行微屈位（约17°）及30°屈曲位膝关节MRI,由2名医师分别对ACL全长、双束结构、断裂ACL的断裂点及残端状况显示进行评分,并以关节镜结果为金标准,计算诊断ACL断裂的敏感度、特异度和准确率。结果 微屈位MRI诊断ACL断裂的敏感度、特异度和准确率分别为97.44%（38/39）、100%（25/25）和98.44%（63/64）,30°屈曲位MRI均为100%,二者诊断ACL断裂的一致性好（Kappa=0.967）。30°屈曲位扫描对ACL全长、断裂点及残端的显示优于微屈位（P均<0.001）,二者对ACL双束结构的显示差异无统计学意义（P=0.223）。结论 30°屈曲位与微屈位MR扫描诊断ACL断裂的敏感度、特异度及准确率均较高,30°屈曲位显示ACL全长及其断裂情况优于微屈位。     

股骨滑车成形联合内侧髌股韧带双束解剖重建治疗髌骨脱位

目的探讨股骨滑车成形联合内侧髌股韧带双束解剖重建治疗髌骨脱位伴有严重股骨滑车发育不良的临床效果。方法回顾性研究自2006年3月至2008年12月在我院诊断为髌骨脱位伴有严重股骨滑车发育不良的患者5例(5膝),接受股骨滑车成形联合内侧髌股韧带双束解剖重建治疗。测量比较手术前后胫骨结节滑车沟间距(TT-TG值),髌股适合角(CA),髌骨倾斜角(PTA),髌骨外移率(PLSR),手术前后的Lysholm膝关节功能评分及Kujala髌股关节不稳症状评分评估手术效果。结果患者术后均获得随访,最短随访时间为3年。术后伤口均Ⅰ期愈合,未发生感染。无复发性髌骨脱位。Kujala髌股关节不稳症状评分从术前的54.20±8.04增加到术后的81.60±3.97,Lysholm膝关节功能评分从术前的54.60±5.22增加到82.60±2.70。术后患者的TT-TG值、CA、PTA、PLSR均恢复到正常范围,与术前相比差异具有统计学意义(P<0.05)。结论对于临床上髌骨脱位伴有严重滑车发育不良的患者采用股骨滑车成形联合内侧髌股韧带双束解剖重建治疗可以有效纠正髌股关节的运动轨迹,改善膝关节功能,临床效果较好。     

磁共振T1ρ和T2mapping成像定量评价早期骨性关节炎

目的 探讨磁共振T1ρ和T2mapping成像评价骨性关节炎（OA）早期软骨损伤的价值。方法 对78例OA患者（轻度OA组50例,重度OA组28例）和23名正常人（正常组）行膝关节软骨MR扫描,包括FSET1W/T2W、自旋锁定T1ρ和T2mapping成像。分别测量股骨软骨平均T1ρ和T2值,采用SPSS18.0统计学软件比较各组间的差异。结果 共86个膝关节516个观察面纳入研究,其中正常组20名,轻度OA组41例,重度OA组25例。65例（143个关节面）出现不同程度软骨损伤,主要位于股骨内侧髁后部。重度OA、轻度OA及正常组平均T1ρ和T2值分别为（48.37±5.80）ms和（48.67±6.05）ms、（44.26±4.16）ms和（45.78±5.85）ms、（40.34±2.10）ms和（42.62±4.15）ms,各组间T1ρ值和T2值差异均有统计学差异（P<0.05）,重度OA组与正常组T2值差异有统计学差异（P<0.05）。结论 T1ρ和T2mapping成像可发现早期软骨损伤,T1ρ敏感度更高,可用于早期诊断骨性关节炎。     

股骨滑车及髌骨发育不良的MRI表现及其临床意义分析

目的：探讨股骨滑车及髌骨发育不良的MRI表现及其与髌股关节紊乱症的相关性。方法膝关节病例组26例（30个膝）及对照组30例（30个膝）均行MRI检查,在股胫关节上方3 cm层面进行测量,对TT-TG间距、股骨滑车前上侧突起、内外侧滑车关节面比例、外侧倾斜角、髌骨Wiberg分型及指数进行定性及定量分析（注释：在观察的指标中,TT-TG间距、股骨滑车前上侧突起、内外侧滑车关节面比例、外侧倾斜角、髌骨Wiber指数为定量分析,髌骨Wiberg分型为定性分析）。结果两组别TT-TG间距（P＝0.02）、滑车前上缘突起（P＝0.00）、外侧倾斜角（P＝0.00）、内外侧关节面比值（P＝0.01）、髌骨Wiberg指数（P＝0.00）的测量值差异均具有非常显著的统计学差异;WibergⅠ-Ⅱ型组与WibergⅢ-Ⅳ型组Wiberg指数的均值具有显著的统计学差异（P＝0.00）。髌骨Wiberg指数与股骨滑车发育形态、髌骨Wiberg分型呈负相关;股骨滑车发育类型与髌骨分型呈正相关。结论股骨滑车与髌骨发育不良常常同时存在（P＝0.00）,成为髌股关节紊乱症的骨发育结构不良的直接原因。MRI横轴位对股骨滑车发育不良的诊断具有非常重要的价值,应纳入膝关节检查的常规扫描。     

Higher patellofemoral compressive force does not affect anterior knee pain in anatomical bi-cruciate retaining total knee arthroplasty: In vivo prospective analysis of guided motion prosthesis

BackgroundThe purposes of the present study are 1) to measure intraoperative patellofemoral compressive force in patients undergoing anatomical bi-cruciate retaining total knee arthroplasty and to assess the relationship between intraoperative patellofemoral compressive force and patient reported outcome measurements and 2) to compare patellofemoral compressive force and patient reported outcome measurements among patients who underwent anatomical bi-cruciate retaining, cruciate retaining, and bi-cruciate stabilized total knee arthroplasty.MethodsTwenty-two patients with varus osteoarthritis of the knee who underwent anatomical bi-cruciate retaining total knee arthroplasty, 20 patients who underwent cruciate retaining total knee arthroplasty, and 24 patients who underwent bi-cruciate stabilized total knee arthroplasty were assessed. Patient reported outcome measurements were evaluated at 1.5 years after surgery.FindingsIntraoperative patellofemoral compressive force was significantly lower with anatomical bi-cruciate retaining total knee arthroplasty than with cruciate retaining total knee arthroplasty at 60° to 140° of flexion and nearly equivalent to intraoperative patellofemoral compressive force with bi-cruciate stabilized total knee arthroplasty at all knee flexion angles examined. With anatomical bi-cruciate retaining total knee arthroplasty, there were no significant correlations between intraoperative patellofemoral compressive force and almost all patient reported outcome measurements except for 2011 Knee Society Score expectations, which was positively correlated with patellofemoral compressive force at 10° of flexion, and Patella score quadriceps strength, which was negatively correlated with patellofemoral compressive force at 60° of flexion.InterpretationThere were no significant correlations between intraoperative patellofemoral compressive force and anterior knee pain after anatomical bi-cruciate retaining total knee arthroplasty.Evidence level: 3.     

膝关节腱鞘巨细胞瘤与色素沉着绒毛结节性滑膜炎的MRI分析

目的 分析膝关节腱鞘巨细胞瘤与色素沉着绒毛结节性滑膜炎的MRI表现特点.方法 回顾性分析经手术病理证实的膝关节腱鞘巨细胞瘤11例、色素沉着绒毛结节性滑膜炎25例,均接受MR检查,其中2例色素沉着绒毛结节性滑膜炎患者接受增强扫描.结果 11例膝关节腱鞘巨细胞瘤中,局限型8例、弥漫型3例;9例位于髌韧带附近,1例位于前交叉韧带,1例位于胭窝;与骨骼肌信号相比,病变T1WI呈等低信号,T2WI以混杂高信号为主;关节软骨破坏2例;关节腔积液9例.25例色素沉着绒毛结节性滑膜炎中,局限型4例,弥漫型21例,4例为手术后复发;增生滑膜在T1WI上呈等或稍低信号,T2WI以等或稍高信号为主,其内可见多发结节或肿块样T1WI、T2WI低信号,2例增强扫描明显强化,信号欠均匀;7例增生滑膜突破关节囊进入胭窝,出现胭窝囊肿5例;肌腱、韧带侵犯19例;骨质破坏20例;关节腔积液19例,其中血性积液12例.结论 MR检查对膝关节腱鞘巨细胞瘤与色素沉着绒毛结节性滑膜炎的诊断及鉴别诊断具有重要价值.     

Biomechanical effects of joint line elevation in total knee arthroplasty

Background

Inadequate restoration of the knee joint line after total knee arthroplasty may lead to a poor clinical outcome. The purpose of this study was to quantitatively assess the effects of joint line elevation following total knee arthroplasty with increased joint volume on patellofemoral contact kinematics.

Methods

Six cadaveric specimens were tested. Patellofemoral contact area, contact pressure, and kinematics were measured following total knee arthroplasty with an anatomic joint line and after 4 and 8 mm of joint line elevation, at knee flexion angles of 0°, 30°, 60°, 90° and 120°. Repeated measures analysis of variance with a Tukey post hoc test with a significance level of 0.05 was used for statistical analyses.

Findings

There was a decrease in contact area with joint line elevation at flexion angles of 60°, 90° and 120° (P = 0.009–0.04). There was a significant increase in contact pressure only at 30° of knee flexion with 8 mm of joint line elevation (P = 0.004). Three of the six specimens showed inferior edge loading of the patella component following 8 mm of joint line elevation at 120° of knee flexion. The sagittal plane patellofemoral angle increased significantly with joint line elevation except for 0° knee flexion (P = 0.0002–0.02).

Interpretation

Knee joint line elevation with increased knee volume significantly affects patellofemoral contact area and kinematics and produced inferior edge loading/impingement between the patella and tibial components, this may result in loss of knee range of motion, postoperative pain, and premature component wear.     

The influence of isolated femur and tibia rotations on patella cartilage stress: a sensitivity analysis

BackgroundTo determine the influence of femur and tibia rotations in the transverse and frontal planes on patella cartilage stress.MethodsPatella cartilage stress profiles of six healthy females were obtained during a squatting task using subject-specific finite element models of the patellofemoral joint (45° of knee flexion). Input parameters for the finite element model included joint geometry, quadriceps muscle forces, and weight-bearing patellofemoral joint kinematics. The femur and tibia of each model were then rotated to 2°, 4°, 6°, 8°, and 10° along their respective axes beyond that of the natural degree of rotation in weight-bearing. The process was repeated for internal rotation, external rotation, adduction, and abduction. Quasi-static loading simulations were performed to quantify average patella cartilage stress.FindingsIncremental femur internal rotation beyond that of the natural rotation resulted in progressively greater patella cartilage stress (41–77%), whereas incremental tibia internal rotation resulted in a decrease in patella cartilage stress (7–10%). Femur and tibia external rotation resulted in a mild increase in patella cartilage stress, but only at 10° (9%). Incremental femur adduction resulted in an increase in patella cartilage stress, but only at 10° (43%). Femur abduction and frontal plane tibia rotation in either direction had no influence on patella cartilage stress.InterpretationFemur internal rotation and adduction resulted in the greatest increases in patella cartilage stress. In contrast, tibia rotations in the transverse and frontal planes had minimal to no influence on patella cartilage stress. These results emphasize the need for clinicians to identify and correct faulty hip kinematics in persons with PFP.     

Two-dimensional frontal plane projection angle can identify subgroups of patellofemoral pain patients who demonstrate dynamic knee valgus

BackgroundIdentifying individuals with patellofemoral pain who demonstrate similar modifiable factors including dynamic knee valgus may be useful in establishing subgroups of patients that can undergo individualised management strategies. However, a lack of objective assessment criteria means that the findings are of limited value to clinicians aiming to distinguish between patients with and without altered frontal plane knee kinematics. Therefore, the aim of the study was to investigate dynamic knee valgus in individuals with and without patellofemoral pain by determining frontal plane knee alignment during functional activity.MethodsThirty recreationally active individuals with patellofemoral pain and 30 non-injured individuals had frontal plane knee alignment assessed via two-dimensional analysis of the frontal plane projection angle during single limb stance and single limb squats to 60° of knee flexion.FindingsIndividuals with patellofemoral pain demonstrated excessive frontal plane knee alignment (P = .003; ES = 0.68) compared to uninjured participants during single limb squats. In addition, assessing frontal plane knee alignment using two-dimensional analysis had fair specificity and sensitivity of discriminating patellofemoral pain injury.InterpretationClinical quantification of two-dimensional frontal plane knee alignment may be utilised to subgroup patients with patellofemoral pain that display dynamic knee valgus during single limb squats. Furthermore, this may be a useful clinical tool to determine individuals that may be at risk of developing pain in the future.     

Impact of intraoperative adjustment method for increased flexion gap on knee kinematics after posterior cruciate ligament-sacrificing total knee arthroplasty

BackgroundIn general, the flexion gap is larger than the extension gap with posterior cruciate ligament-sacrificing total knee arthroplasty. Several methods compensate for an excessive flexion gap, but their effects are unknown. The purpose of this study was to compare three methods to compensate for an increased flexion gap.MethodsIn this study, squatting in knees with excessive (4 mm) and moderate (2 mm) flexion gaps was simulated in a computer model. Differences in knee kinematics and kinetics with joint line elevation, setting the femoral component in flexion, and using a larger femoral component as compensatory methods were investigated.FindingsThe rotational kinematics during flexion with setting the femoral component in flexion were opposite to those in the other models. Using a larger femoral component resulted in the most physiological motion. The peak anterior translation was 10 mm in the joint line elevation model compared with approximately 6 mm in the other models. In the joint line elevation model, patellofemoral contact stress was excessively increased at 90° of knee flexion. In contrast, tibiofemoral contact stress was higher during knee extension with setting the femoral component in flexion due to anterior impingement. There were few differences in the effect of the three compensatory methods with a moderate flexion gap.InterpretationA larger femoral component should be used to compensate for an excessive flexion gap because it has less negative impact on posterior cruciate ligament-sacrificing total knee arthroplasty, whereas any compensation method might be acceptable for a moderate flexion gap.     

Tibial tuberosity anteriomedialization vs. medial patellofemoral ligament reconstruction for treatment of patellar instability related to malalignment: Computational simulation

BackgroundMedial patellofemoral ligament reconstruction and tibial tuberosity anteromedialization are common treatment options for recurrent lateral patellar instability, although ligament reconstruction is not commonly applied to knees with lateral malalignment.MethodsMultibody dynamic simulation was used to assess knee function following tibial tuberosity anteromedialization and medial patellofemoral ligament reconstruction for knees with lateral malalignment. Dual limb squatting was simulated with six models representing knees being treated for patellar instability with an elevated tibial tuberosity to trochlear groove distance. The patellar tendon attachment on the tibia was shifted medially (10 mm) and anteriorly (5 mm) to represent tibial tuberosity anteromedialization. A hamstrings tendon graft was represented for medial patellofemoral ligament reconstruction. Patellar tracking was quantified based on bisect offset index. The patellofemoral contact pressure distribution was quantified using discrete element analysis. Data were analyzed with repeated measures comparisons with post-hoc tests.FindingsBoth procedures significantly reduced bisect offset index, primarily at low flexion angles. The decrease was larger for tibial tuberosity anteromedialization, peaking at 0.18. Tibial tuberosity anteromedialization shifted contact pressures medially, significantly increasing the maximum medial contact pressure at multiple flexion angles, with the maximum pressure increasing up to 1 MPa.InterpretationThe results indicate tibial tuberosity anteromedialization decreases lateral patellar maltracking more effectively than medial patellofemoral ligament reconstruction, but shifts contact pressure medially. Tibial tuberosity anteromedialization is likely to reduce the risk of post-operative instability compared to medial patellofemoral ligament reconstruction. The medial shift in the pressure distribution should be considered for knees with medial cartilage lesions, however.     

膝类风湿关节炎与骨关节炎的MRI与病理对照研究

目的：对比分析膝类风湿关节炎（Rheumatoid arthritis,RA）与骨关节炎（Osteoarthritis,OA）的MRI和病理表现特点,进一步分析RA的病变机制.方法：收集我院确诊的行全膝关节置换术（Total knee arthroplasty,TKA）并进行组织病理学检查的RA患者12例和OA患者10例,比较二者的MRI表现以及所对应部位组织病理学的表现特点.结果：膝RA及OA组髌股关节、胫股内侧关节软骨病变差异无统计学意义（P＞0.05）,胫股外侧关节软骨病变差异具有显著统计学意义（P＜0.05）,胫股内、外关节软骨下骨病变差异具有统计学意义（P＜0.05）,膝RA及OA组内、外半月板前角、体部、后角病变差异具有显著统计学意义（P＜0.05）.膝RA关节软骨、软骨下骨及半月板病理学发现大量炎细胞浸润、血管增生,OA组仅见软骨纤维化、半月板基质黏液性变性,少见炎细胞、血管增生.结论：RA组膝关节各部分的破坏程度普遍高于OA组,病理学提示可能与血管炎有关.     

Activation of the quadriceps muscle during semisquatting with different hip and knee positions in patients with anterior knee pain.

OBJECTIVE: We measured the surface electromyographic activities of vastus medialis obliquus and vastus lateralis in 16 subjects with patellofemoral joint pain syndrome. DESIGN: Each subject performed bilateral static knee extension exercises at 60% of his or her maximal voluntary effort under different combinations of hip rotation (30 degrees of medial rotation, neutral, 45 degrees of lateral rotation) and knee flexion (20 and 40 degrees) in a standing position. The ratio of surface-integrated electromyographic signals of vastus medialis obliquus over vastus lateralis was calculated for each of the six conditions. Because of significant interaction of hip rotation and knee flexion in the two-way analysis of variance, data were analyzed separately with paired t tests for the effect of knee positions and one-way repeated measures analysis of variance for hip positions. RESULTS: At 20 degrees of knee flexion, there was no significant difference among the three hip positions, whereas at 40 degrees of knee flexion, medial rotation of the hip resulted in significantly higher vastus medialis obliquus over vastus lateralis activity ratio than lateral rotation (P < 0.05). CONCLUSIONS: There was relatively more activation of vastus medialis obliquus than vastus lateralis at 40 degrees of semisquat with the hip medially rotated by 30 degrees. This finding has clinical implications for training the vastus medialis obliquus in patients with patellofemoral joint pain syndrome.