Topical administration of the nitric oxide donor glyceryl trinitrate modifies the structural and biomechanical properties of ovine articular cartilage

Objective: To examine the effect of topical administration of glyceryl trinitrate (GTN), an exogenous nitric oxide (NO) donor, on the structural and biomechanical properties of uncalcified articular cartilage (UCC) in aged ewes.Design: Twelve ewes were used for this study. Six of these were treated with 2% GTN ointment (0.7 mg/kg) twice per week (GTN), and the remaining six were used as normal controls (NOC). After sacrifice at 26 weeks, dynamic biomechanical indentation testing and thickness determination (by needle penetration) were performed on tibial plateau articular cartilage at 18 locations. Using histological sections prepared from the lateral and medial femoral condyles (LFC, MFC) and tibial plateau (LTP, MTP), the thickness of UCC, cartilage proteoglycan content (intensity of toluidine blue staining; LFC, MFC only), and collagen birefringence (LTP, MTP, LFC only) were quantified by computer-assisted image analysis.Results: Phase lag of tibial plateau cartilage was reduced in GTN sheep relative to NOC (mean of all testing locations 11.0±1.9° vs 12.1±2.3°; P=0.0001). GTN treatment also globally reduced UCC thickness across the joint (ANOVA for all measured zones, P<0.0001). UCC thinning was most pronounced in the MFC (P=0.025) and LTP (P=0.0002). Proteoglycan content was reduced in the MFC(P=0.019), while collagen birefringence was increased in superficial cartilage zones of the LTP.Conclusions: NO donation via topical administration of GTN to normal ewes reduced the thickness and phase lag of femoro-tibial articular cartilage, suggesting a disturbance in chondrocyte metabolism. Regional alterations of collagen organisation and proteoglycan content were consistent with this interpretation.     

健康青年人的膝关节软骨厚度3.0T MRI的定量研究

目的:探讨3.0T MRI精确测量健康青年膝关节软骨厚度为骨关节炎的定量诊断和关节置换精准截骨提供可靠的解剖参数。方法:自2013年1月至2013年12月于吉林省长春地区招募30名健康青年志愿者,男14名,女16名,年龄22~33(25.8±2.4)岁。对每名志愿者的双膝关节进行3.0 T MRI扫描,对股骨外侧髁(lateralis femoris condylus,LFC)、股骨内侧髁(medialis femorisc ondylus,MFC)、胫骨外侧平台(lateral tibial plateau,LTP)、胫骨内侧平台(medial tibial plateau,MTP)进行软骨厚度测量。结果:在LFC、MFC、LTP、MTP 4个区域中,无论青年男性或女性,左、右侧膝关节软骨厚度比较,差异均无统计学意义(P>0.05);健康青年男性与女性之间膝关节软骨厚度比较,差异有统计学意义(P<0.05)。在同一性别组,LFC软骨厚度中间较薄,前、后方较厚;MFC软骨厚度前方最薄,从前方向后方逐渐增厚;LTP软骨厚度中间最厚,后方次之,前方最薄;MTP软骨厚度前方最薄,中间、后方相对均匀且均较前方厚。结论:在我国22~33岁正常健康青年人中,性别差异可能是膝关节各个区域软骨厚度差异的重要因素。无论男性或女性健康青年人,整个膝关节软骨厚度分布不均匀,但左、右侧膝关节相同区域软骨厚度无明显差异。     

影响骨关节炎患者全膝关节置换术后关节功能的相关因素分析

[目的]探讨影响骨关节炎患者全膝关节置换术后关节功能的相关因素.[方法]对41例43膝骨关节炎终末期行全膝关节置换术(total knee arthroplasty,TKA)患者术前、术后半年的膝关节功能进行HSS评分,应用Pearson相关分析及多重线性回归对术后膝关节HSS评分与患者年龄、体重指数、疼痛评分、术前膝关节活动度(ROM)、内翻畸形程度、手术前后股骨前髁偏距(ACO)变化情况,术后胫骨平台后倾角(PSA)等因素进行统计分析;并分析手术前后股骨前髁偏距(ACO)变化情况,术后胫骨平台后倾角(PSA)与术后膝关节ROM之间的关系.[结果]Pearson相关分析结果可以看出术前疼痛评分、术前膝关节ROM、术后胫骨平台PSA、手术前后股骨ACO变化与术后膝关节功能HSS评分呈正相关;体重指数、膝内翻畸形程度与术后膝关节功能HSS评分呈负相关.逐步回归分析经筛选后纳入方程的变量只有术后胫骨平台PSA (P＜0.01)、术前疼痛功能评分(P＜0.01)、体重指数(P＜0.05),根据标准回归系数的绝对值大小排序,对应变量的作用排序为术后胫骨平台PSA (0.555)＞术前疼痛评分(0.357)＞体重指数(0.187).ACO术前大于术后组的患者术后膝关节ROM明显好于ACO术前小于术后组(P＜0.05).术后胫骨平台PSA 7°～9°组术后膝关节活动度最好.[结论](1)术前疼痛评分、术前膝关节ROM、术后胫骨平台PSA、术前术后股骨ACO变化与术后膝关节HSS评分呈正相关,体重指数、膝关节内翻畸形与术后膝关节功能HSS评分呈负相关;(2)术后胫骨平台PSA、术前疼痛评分、体重指数对术后半年膝关节HSS评分影响显著;(3)股骨ACO变化对术后膝关节活动度有影响,术后胫骨平台PSA7°～9°膝关节活动度好.     

Ovariectomy alters the structural and biomechanical properties of ovine femoro-tibial articular cartilage and increases cartilage iNOS

OBJECTIVE: To examine the effect of oestrogen depletion produced by surgical ovariectomy on the structural and biomechanical properties of ovine femoro-tibial articular cartilage (AC), and the production of inducible nitric oxide synthase (iNOS) and nitrotyrosine by these tissues. METHODS: Six aged ewes were surgically ovariectomised (OVX), while six were used as unoperated controls. Dynamic biomechanical indentation testing of tibial plateau AC was performed at 26 weeks post-op. Histological sections of medial tibial plateau and lateral tibial plateau (LTP), medial and lateral femoral condyles (MFC, LFC) and patellar AC were examined for histopathology, toluidine blue staining intensity, and patterns of collagen birefringence intensity. Immunoreactivity for iNOS and nitrotyrosine was assessed in full-thickness biopsy plugs of LFC and patellar AC, and patellar AC explants were cultured to determine in vitro NO release. RESULTS: Phase lag was reduced overall in LTP-AC of OVX sheep (10.9+/-2.2 degrees vs 12.1+/-2.3 degrees ; P<0.0001). Cartilage thickness was reduced in the LTP of OVX sheep (P=0.0002), in association with localised changes in dynamic shear modulus. Toluidine blue staining intensity was reduced in the patella, LFC, and MFC. Histological examination revealed greater histopathology scores in the MFC of OVX animals, and altered collagen birefringence intensity plots in the LTP. Immunostaining for iNOS was increased in patella AC (P=0.008), whilst nitrotyrosine immunoreactivity was increased in patella (P=0.03) and LFC (P<0.0001) AC. NO release by patellar AC explants was also elevated. CONCLUSIONS: Oestrogen depletion induced by OVX caused regional thinning of femoro-tibial cartilage, with biomechanical and histological changes suggestive of a disturbance in the content and/or structural organisation of the proteoglycan and collagen macromolecular assembly. The observed up-regulation of cartilage iNOS suggests a possible mechanism for these matrix changes.     

The nitric oxide donor glyceryl trinitrate increases subchondral bone sclerosis and cartilage degeneration following ovine meniscectomy

AIM: To examine the effect of glyceryl trinitrate (GTN), a nitric oxide (NO) donor compound, on the concurrent progression of cartilage and subchondral bone changes in an ovine meniscectomy model of osteoarthritis (OA). METHODS: Bilateral lateral meniscectomy (MX) was performed on 12 ewes to induce OA. Six were treated with topical GTN (0.7mg/kg twice weekly) (MX+GTN). Six other sheep formed non-operated controls (NOC). After sacrifice at six months, the subchondral bone density (BMD) of the lateral and medial femoral condyles (LFC, MFC) and tibial plateau (LTP, MTP) was assessed by DEXA. Dynamic biomechanical testing was performed across the MTP and LTP. Histological sections from each region were scored qualitatively and the thickness of the subchondral bone plate (SCB) was determined by image analysis. RESULTS: MX+GTN displayed significantly greater SCB thickness relative to MX in the LFC (mean increase +88% and +42%, respectively) and the MFC. SCB BMD was 10-12% greater in MX+GTN relative to MX in the LFC, LTP and MTP. MX+GTN sheep also showed greater increases in some histopathology variables, greater central erosion of the LTP, and changes in dynamic stiffness (decreased) and phase lag (increased) in the outer zone of the LTP. CONCLUSIONS: Treatment with GTN significantly increased subchondral bone thickness and density during subchondral remodelling following meniscectomy. In addition, it slightly but significantly worsened degeneration of cartilage structure and function. These results suggest that clinical use of GTN may accelerate both cartilage degeneration and subchondral bone sclerosis if used in the presence of OA, and demonstrate that NO has the potential be an important mediator of the subchondral bone changes seen in OA.     

Hyaluronic acid and chondroitin sulfate content of osteoarthritic human knee cartilage: Site‐specific correlation with weight‐bearing force based on femorotibial angle measurement

This study analyzed glycosaminoglycan (GAG) content in specific compartments of the knee joint to determine the impact of malalignment and helped refine indications for osteotomy. To assess malalignment, the radiological femorotibial angle (FTA) was measured and knee joints were also graded for OA severity with the Kellgren/Lawrence (K/L) classification. Cartilage samples were obtained from 36 knees of 32 OA patients undergoing total knee replacement surgery. Explants were harvested from the medial femoral condyle (MFC), lateral femoral condyle (LFC), patellar groove (PG), and lateral posterior femoral condyle (LPC). Concentrations of hyaluronic acid (HA) and chondroitin sulfate (CS) were measured by high‐performance liquid chromatography (HPLC). With OA severity, the average FTA significantly increased. HA and CS content in MFC was negatively correlated with radiographic FTA. In LFC, HA ratio, which is HA content in lateral condyle divided by medial condyle and chondroitin 6 sulfate, increased until about 190° FTA. Importantly, at >190° these contents were significantly decreased. HA and CS content of the femoral condyle shows topographic differences that are related to OA grade and weight‐bearing force based on FTA. The clinical relevance is that osteotomy may not be indicated for patients with severe varus (>190°) abnormalities. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1194–1198, 2008     

Flexion Space Balancing Through Component Positioning and Its Relationship to Traditional Anatomic Rotational Landmarks in Robotic Total Knee Arthroplasty

BackgroundThe use of the femoral component position to balance the flexion space and its relationship to the transepicondylar axis (TEA) and posterior condylar angle (PCA) has not been thoroughly evaluated.MethodsA total of 233 patients undergoing robotic arm–assisted total knee arthroplasty were evaluated. Native TEA and PCA were established on preoperative computed tomography scans. Femoral component rotation was set in the axial plane to match the native trochlea and native medial femoral condyle to set the flexion gap. Knee flexion space gaps and component position were recorded. The relationship of the femoral component to the native TEA, PCA, and preoperative radiographic landmarks was evaluated.ResultsThe intraoperative measured medial flexion space gap did not significantly correlate with the relationship of the femoral component to the PCA or TEA in varus or valgus knees. In varus knees, the preoperative mechanical axis alignment had a positive relationship to femoral component position when compared to the PCA (P = .04) and TEA (P = .002). In valgus knees, there was a positive correlation between the preoperative lateral distal femoral angle and component position when compared to the PCA (P = .04) only.ConclusionIntraoperative measured flexion space balance through femoral component positioning did not correlate with its relationship to the native TEA or PCA. In varus knees, the preoperative mechanical axis alignment correlated with an increase in femoral component external rotation to the TEA and PCA. In valgus knees, the severity of preoperative lateral distal femoral angle correlated with the rotational relationship of the femoral component to the PCA only.     

Comparison of kinematic analysis by mapping tibiofemoral contact with movement of the femoral condylar centres in healthy and anterior cruciate ligament injured knees.

Two methods of analysis of knee kinematics from magnetic resonance images (MRI) in vivo have been developed independently: mapping the tibiofemoral contact, and tracking the femoral condylar centre. These two methods are compared for the assessment of kinematics in the healthy and the anterior cruciate ligament injured knee. Sagittal images of both knees of 20 subjects with unilateral anterior cruciate ligament injury were analysed. The subjects had performed a supine leg press against a 150 N load. Images were generated at 15 degrees intervals from 0 degrees to 90 degrees knee flexion. The tibiofemoral contact, and the centre of the femoral condyle (defined by the flexion facet centre (FFC)), were measured from the posterior tibial cortex. The pattern of contact in the healthy knee showed the femoral roll back from 0 degrees to 30 degrees, then from 30 degrees to 90 degrees the medial condyle rolled back little, while the lateral condyle continued to roll back on the tibial plateau. The contact pattern was more posterior in the injured knee (p=0.012), particularly in the lateral compartment. The medial FFC moved back very little during knee flexion, while the lateral FFC moved back throughout the flexion arc. The FFC was not significantly different in the injured knee (p=0.17). The contact and movement of the FFC both demonstrated kinematic events at the knee, such as longitudinal rotation. Both methods are relevant to design of total knee arthroplasty: movement of the FFC for consideration of axis alignment, and contact pattern for issues of interface wear and arthritic change in ligament injury.     

Predictive validity of radiographic signs of complete discoid lateral meniscus in children using machine learning techniques

The diagnostic utility of radiographic signs of complete discoid lateral meniscus remains controversial. This study aimed to investigate the diagnostic accuracy and determine which sign is most reliably detects the presence of a complete discoid lateral meniscus in children. A total of 141 knees (age 7-16) with complete discoid lateral meniscus and 141 age- and sex-matched knees with normal meniscus were included. The following radiographic signs were evaluated: lateral joint (LJ) space, fibular head (FH) height, lateral tibial spine (LTS) height, lateral tibial plateau (LTP) obliquity, lateral femoral condyle (LFC) squaring, LTP cupping, LFC notching, and prominence ratio of the femoral condyle. Prediction models were constructed using logistic regressions, decision trees, and random forest analyses. Receiver operating characteristic curves and area under the curve (AUC) were estimated to compare the diagnostic accuracy of the radiographic signs and model fit. The random forest model yielded the best diagnostic accuracy (AUC: 0.909), with 86.5% sensitivity and 82.2% specificity. LJ space height, FH height, and prominence ratio showed statistically large AUC compared with LTS height and LTP obliquity (P < .05 in all). The cut-off values for diagnosing discoid meniscus to be <12.55 mm for FH height, <0.804 for prominence ratio, and >6.6 mm for LJ space height when using the random forest model. On the basis of the results of this study, in clinical practice, LJ space height, FH height and prominence ratio could be easily used as supplementary tools for complete discoid lateral meniscus in children.     

微创膝关节单髁置换术股骨髓内定位与髓外定位假体位置的影像学比较

[目的]通过对膝关节单髁置换术股骨假体的力线测量,评价股骨髓外定位法指导假体放置的有效性.[方法]回顾性分析2007年5月～2010年5月采用微创单髁置换术治疗膝关节内侧间室骨性关节炎的患者73例(80膝),其中股骨髓内定位组(intramedullary alignment guide,IM) 54例(56膝),男23例(23膝),女31例(33膝);股骨髓外定位组(extramedullary alignment guide,EM)19例(24膝),男9例(10膝),女10例(14膝).测量术后即刻股骨假体内翻/外翻和屈/伸力线.[结果]IM组股骨假体内翻/外翻力线为0.59°内翻±3.98°,EM组股骨假体力线平均为0.81°外翻±3.30°,P=0.235 2.IM组股骨假体屈/伸力线为0.70°伸直±3.89°,EM组股骨假体力线为1.12°伸直±3.43°,P=0.564 3.[结论]微创膝关节单髁置换术股骨髓内定位可取得与髓外定位法相同优良的股骨假体力线.     

固定平台后稳定型假体全膝关节置换术后的运动学研究

 目的 探讨固定平台后稳定型假体全膝关节置换(total knee arthroplasty,TKA)术后膝关节在负重屈膝下蹲时的运动学特征。方法 选取10名健康志愿者和10例固定平台后稳定型假体TKA术后患者。制作骨骼及膝关节假体三维模型,在持续X线透视下完成负重下蹲动作,膝关节屈曲度每增加15°截取一幅图像。通过荧光透视分析技术完成三维模型与二维图像的匹配,再现股骨与胫骨在屈膝过程中的空间位置,通过连续的图像分析比较正常与固定平台后稳定型假体TKA术后膝关节在负重下蹲时股骨内、外髁前后移动及胫骨内外旋转幅度。结果 负重下蹲时,正常膝关节平均屈曲136°,股骨内、外髁分别后移(7.3±1.2) mm和(19.3±3.1) mm,胫骨平均内旋23.8°±3.4°;TKA术后膝关节平均屈曲125°,股骨内、外髁分别后移(1.4±1.6) mm和(6.4±1.7) mm,胫骨平均内旋8.5°±3.4°。结论 固定平台后稳定型假体TKA术后膝关节运动与正常膝关节相似,均表现出股骨内、外髁后移及胫骨内旋运动,但幅度小于正常膝关节,且在屈膝过程中存在股骨矛盾性前移及胫骨外旋现象。     

Editorial Commentary: Knee Lateral Femoral Osteochondral Allografts Are Not Recommended for Medial Femoral Condylar Defects: If the Shoe Doesn’t Fit,Don’t Wear It!

Treatment of large articular cartilage defects of the knee is challenging, particularly in young, high-demand patients. Osteochondral allograft (OCA) transplantation is a viable treatment option, providing fully mature articular cartilage during a single operation while avoiding donor site morbidity. Indications are symptomatic, full-thickness articular cartilage defects >3 cm². Contraindications include a “kissing” lesion of the corresponding articular cartilage surface, uncorrected ligamentous instability, malalignment, peripheral osteophytes, joint-space narrowing, or absence of >50% of the meniscus in the affected compartment. Matching for size and contour is crucial; therefore, we use medial femoral condyle (MFC) allografts for MFC lesions and lateral femoral condyle (LFC) allografts for LFC lesions, and do not recommend LFC grafts for the MFC. Survival rates are 78.7% and 72.8% at 10 and 15 years, respectively.     

Varus tibial joint line obliquity: a potential cause of femoral component malrotation.

In 60 consecutive total knee arthroplasties done in 52 patients with primary osteoarthritis and varus or neutral tibiofemoral alignment, the posterior condylar angle was calculated intraoperatively and averaged 3.98 degrees (range, 0 degrees-9 degrees). Eighteen knees had a posterior condylar angle value less than 3 degrees whereas 27 knees had a posterior condylar angle value of 5 degrees or greater. Final rotational alignment of the femoral component was set parallel to the transepicondylar axis. Only one of these 60 knees required a lateral retinacular release for proper patellar tracking during the knee arthroplasty. When compared with three previously defined angles measured on the radiographs taken preoperatively, only the tibial plateau-tibial shaft angle values were correlated significantly with the value of the posterior condylar angle. As the tibial varus joint line obliquity increased, there was a distinct tendency for the transepicondylar axis to be rotated more externally relative to the posterior condylar axis. This variance suggests that the use of the posterior condylar axis as a rotational reference is inappropriate in many knees with arthritis with varus or neutral tibiofemoral alignment. In particular, varus tibial joint line obliquity of more than 4 degrees increases the likelihood of femoral component malrotation when the posterior femoral condyles are used to reference femoral component rotation.     

全膝关节置换术后股胫关节运动学轨迹的数字化模型研究

 目的 通过透视技术结合数字化模型注册技术分析全膝关节置换术后股骨假体与胫骨垫片之间的相对运动和接触位置。方法 2007年7月至2008年6月,接受GENESISⅡ假体全膝关节置换术患者16例,均为女性;年龄56～76岁,平均66.4岁。随访48～60个月,平均(56±3)个月。采用膝关节学会评分(Knee Society Score,KSS)评价膝关节功能;采用循环透视方法获取影像学数据,对假体逆向数字建模,进行数字模型和影像学数据的匹配,重建膝关节的三维运动;测量股骨内、外髁接触位置的移动,计算胫骨内旋角度,测量股骨凸轮和胫骨立柱的接触时相和范围。结果 末次随访时KSS膝评分(93±5)分,功能评分(88±13)分,与术前比较差异有统计学意义。股骨内髁的移动范围(8.5±2.5) mm,外髁的移动范围(9.5±4.8) mm,胫骨内旋角度2.5°±8.4°。屈膝约30°～40°时凸轮和立柱发生接触,立柱后方的接触范围(8.0±1.8) mm。胫骨平台后倾角度越大,凸轮和立柱的接触越晚。结论 全膝关节置换术后股胫关节的运动学特征与正常膝关节不同,膝关节屈曲10°~30°时股骨内髁前移,屈曲大于40°后股骨内、外髁后移,胫骨平台后倾与凸轮和立柱的接触时相有相关性。     

Rotational profile of lower limb and axis for tibial component alignment in varus osteoarthritic knees

The purposes of this study were to describe the changes in tibial torsion and knee rotation in varus osteoarthritic knees and to check the reliability of reference axis, for tibial component placement, based on femoral transepicondylar axis in these patients. A secondary goal was to determine which reference axis based on proximal tibia is most accurate for determining tibial component rotation. Fifty-two varus osteoarthritic knees and 20 normal knees were analyzed using computed tomographic scan. Tibial torsion and knee rotation were significantly reduced in patients with osteoarthritis. Reference axis based on posterior tibial condyles was most accurate and least variable for tibial component alignment. A significant negative correlation was found between knee rotation and tibial axis based on transepicondylar axis (r = -0.485).     

Subchondral bone strength in arthrosis: Cadaver studies of tibial condyles

We measured the axial penetration strength of subchondral cancellous bone in a close, regular pattern at the tibial resection surface of five valgus and seven varus human, cadaveric knees. The strength patterns obtained were illustrated by pseudo-three-dimensional reconstructions of strength values as a function of the location on the resection surface. The varus knees had high strength values towards the medial margin of the medial condyle. Three qualitatively different strength patterns were distinguished in the valgus knees: two knees showed a near normal strength distribution with higher peak values medially; two knees with centrolateral bony attrition had high bone strength values at the center of the lateral condyle; and one knee with moderate posterolateral bony attrition showed a high strength area at the posterolateral aspect of the lateral condyle. In both types of malalignment, there was a decrease of bone strength with the depth from the resection surface.     

Double-elevating osteotomy for late-presenting infantile Blount's disease: the importance of concomitant lateral epiphysiodesis

We reviewed 34 knees in 24 children after a double-elevating osteotomy for late-presenting infantile Blount's disease. The mean age of patients was 9.1 years (7 to 13.5). All knees were in Langenski?ld stages IV to VI. The operative technique corrected the depression of the medial joint line by an elevating osteotomy, and the remaining tibial varus and internal torsion by an osteotomy just below the apophysis. In the more recent patients (19 knees), a proximal lateral tibial epiphysiodesis was performed at the same time. The mean pre-operative angle of depression of the medial tibial plateau of 49 degrees (40 degrees to 60 degrees ) was corrected to a mean of 26 degrees (20 degrees to 30 degrees ), which was maintained at follow-up. The femoral deformity was too small to warrant femoral osteotomy in any of our patients. The mean pre-operative mechanical varus of 30.6 degrees (14 degrees to 66 degrees ) was corrected to 0 degrees to 5 degrees of mechanical valgus in 29 knees. In five knees, there was an undercorrection of 2 degrees to 5 degrees of mechanical varus. At follow-up a further eight knees, in which lateral epiphysiodesis was delayed beyond five months, developed recurrent tibial varus associated with fusion of the medial proximal tibial physis.     

Motion of the femoral condyles in flexion and extension during a continuous lunge

Numerous studies have reported on in‐vivo posterior femoral condyle translations during various activities of the knee. However, no data has been reported on the knee motion during a continuous flexion‐extension cycle. Further, few studies have investigated the gender variations on the knee kinematics. This study quantitatively determined femoral condylar motion of 10 male and 10 female knees during a continuous weightbearing flexion‐extension cycle using two‐dimensional to three‐dimensional fluoroscopic tracking technique. The knees were CT‐scanned to create three‐dimensional models of the tibia and femur. Continuous images of each subject were taken using a single‐fluoroscopic imaging system. The knee kinematics were measured along the motion path using geometric center axis of the femur. The results indicated that statistical differences between the flexion and extension motions were only found in internal‐external tibial rotation and lateral femoral condylar motion at the middle range of flexion angles. At low flexion angles, male knees have greater external tibial rotation and more posteriorly positioned medial femoral condyle than females. The knee did not show a specific pivoting type of rotation with flexion. Axial rotation center varied from lateral to medial compartments of the knee. These data could provide useful information for understanding physiological motion of normal knees. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:591–597, 2015.