A new method to measure post-traumatic joint contractures in the rabbit knee

A new device and method to measure rabbit knee joint angles are described. The method was used to measure rabbit knee joint angles in normal specimens and in knee joints with obvious contractures. The custom-designed and manufactured gripping device has two clamps. The femoral clamp sits on a pinion gear that is driven by a rack attached to a materials testing system. A 100 N load cell in series with the rack gives force feedback. The tibial clamp is attached to a rotatory potentiometer. The system allows the knee joint multiple degrees-of-freedom (DOF). There are two independent DOF (compression-distraction and internal-external rotation) and two coupled motions (medial-lateral translation coupled with varus-valgus rotation; anterior-posterior translation coupled with flexion-extension rotation). Knee joint extension-flexion motion is measured, which is a combination of the materials testing system displacement (converted to degrees of motion) and the potentiometer values (calibrated to degrees). Internal frictional forces were determined to be at maximum 2% of measured loading. Two separate experiments were performed to evaluate rabbit knees. First, normal right and left pairs of knees from four New Zealand White (NZW) rabbits were subjected to cyclic loading. An extension torque of 0.2 Nm was applied to each knee. The average change in knee joint extension from the first to the fifth cycle was 1.9 deg +/- 1.5 deg (mean +/- sd) with a total of 49 tests of these eight knees. The maximum extension of the four left knees (tested 23 times) was 14.6 deg +/- 7.1 deg, and of the four right knees (tested 26 times) was 12.0 deg +/- 10.9 deg. There was no significant difference in the maximum extension between normal left and right knees. In the second experiment, nine skeletally mature NZW rabbits had stable fractures of the femoral condyles of the right knee that were immobilized for five, six or 10 weeks. The left knee served as an unoperated control. Loss of knee joint extension (flexion contracture) was demonstrated for the experimental knees using the new methodology where the maximum extension was 35 deg +/- 9 deg, compared to the unoperated knee maximum extension of 11 deg +/- 7 deg, 10 or 12 weeks after the immobilization was discontinued. The custom gripping device coupled to a materials testing machine will serve as a measurement test for future studies characterizing a rabbit knee model of post-traumatic joint contractures.     

Operative management and outcome of complex wounds following total knee arthroplasty.

This study describes the treatment protocol for and the outcome of the management of complex wounds around total knee replacements. An analysis of 28 patients (29 knees) with complex defects who had surgery between January 1, 1986, and July 30, 1996, was performed. A specific management protocol was applied to each knee on the basis of the size and depth of the wound, the presence of infection, and the quality of soft tissue. Primary treatment included local wound care, debridement, and skin grafting or coverage with a fasciocutaneous flap, pedicled muscle flap, or free muscle transfer. Postoperatively, knees were evaluated using the Knee Society objective score. Successful salvage of the lower extremity was obtained in 28 knees (97 percent) and of the knee prosthesis in 24 of 29 knees (83 percent). Secondary plastic surgery procedures were necessary in five knees (17 percent), and secondary orthopedic procedures were necessary in four knees (14 percent). Successful salvage of total knee arthroplasty in the presence of a complex wound requires early identification of infection, aggressive irrigation and debridement, and early appropriate soft-tissue coverage. The use of our proposed algorithm will facilitate management of these complex wounds.     

Biofeedback as a means to alter electromyographic activity in a total knee replacement patient

This paper presents a single case controlled study of a 75-year-old male having bilateral total knee replacement. Baseline EMG recordings demonstrated differential levels of vastus medialis and vastus lateralis muscle activity in both knees during exercise, with increased vastus lateralis activity compared to vastus medialis activity. The purpose of the study was to use electromyographic (EMG) biofeedback training to train the patient to equalize vastus medialis and vastus lateralis EMG activity during exercise. After 11 and 13 training sessions for the left and right knees, respectively, differences between vastus medialis and vastus lateralis activity had markedly decreased. Following the termination of biofeedback training, EMG activity during exercise showed a return toward baseline levels. Several concomitant changes in psychological and physical function were noted. These results suggested that EMG biofeedback can be used to train vastus medialis and vastus lateralis activity in total knee replacement patients, and that biofeedback training may produce positive benefits in other functional areas.     

全膝关节置换术后皮温与血清指标变化的相关性研究

目的:研究膝骨性关节炎(knee osteoarthritis,KOA)患者行单侧全膝关节置换术手术前后膝关节皮温、血清指标的变化规律以及与膝关节功能恢复之间相关性。方法:将2016年9月-2017年3月在我院行单侧全膝关节置换术且术后未发生假体周围感染的患者作为研究对象,测量并记录基本信息、术前及术后膝关节皮温、血清指标及膝关节功能评分,并进行统计学分析。结果:本研究共收集病例65例,随访时间为6个月。双膝皮温、双膝皮温差于术后第5天达到峰值,PCT、CRP、ESR均于术后第3天达到峰值,IL-6、WBC于术后第1天达到峰值,HGB下降至最低水平为术后5-7天。患者非手术侧膝关节皮温于术后30天恢复至术前水平,而手术侧膝关节皮温及双膝皮温差直至术后6个月仍未恢复至术前水平;PCT、IL-6、CRP于术后60天恢复至术前水平,ESR于术后90天恢复至术前水平,WBC于术后15天恢复至术前水平。结论:KOA患者TKA术后双膝皮温差直至术后6月仍高于术前水平,而研究中的各项血清指标均于术后3月内恢复至术前水平。     

Biofeedback as a means to alter electromyographic activity in a total knee replacement patient

This paper presents a single case controlled study of a 75-year-old male having bilateral total knee replacement. Baseline EMG recordings demonstrated differential levels of vastus medialis and vastus lateralis muscle activity in both knees during exercise, with increased vastus lateralis activity compared to vastus medialis activity. The purpose of the study was to use electromyographic (EMG) biofeedback training to train the patient to equalize vastus medialis and vastus lateralis EMG activity during exercise. After 11 and 13 training sessions for the left and right knees, respectively, differences between vastus medialis and vastus lateralis activity had markedly decreased. Following the termination of biofeedback training, EMG activity during exercise showed a return toward baseline levels. Several concomitant changes in psychological and physical function were noted. These results suggested that EMG biofeedback can be used to train vastus medialis and vastus lateralis activity in total knee replacement patients, and that biofeedback training may produce positive benefits in other functional areas.The authors wish to express thanks to Dr. Karen Gil for her helpful comments on a draft of this article, and Christianne Herman and Allison Roodman for their help in data collection and entry.     

Cost-effectiveness of total hip and knee replacements for the Australian population with osteoarthritis: discrete-event simulation model

Background

Osteoarthritis constitutes a major musculoskeletal burden for the aged Australians. Hip and knee replacement surgeries are effective interventions once all conservative therapies to manage the symptoms have been exhausted. This study aims to evaluate the cost-effectiveness of hip and knee replacements in Australia. To our best knowledge, the study is the first attempt to account for the dual nature of hip and knee osteoarthritis in modelling the severities of right and left joints separately.

Methodology/Principal Findings

We developed a discrete-event simulation model that follows up the individuals with osteoarthritis over their lifetimes. The model defines separate attributes for right and left joints and accounts for several repeat replacements. The Australian population with osteoarthritis who were 40 years of age or older in 2003 were followed up until extinct. Intervention effects were modelled by means of disability-adjusted life-years (DALYs) averted. Both hip and knee replacements are highly cost effective (AUD 5,000 per DALY and AUD 12,000 per DALY respectively) under an AUD 50,000/DALY threshold level. The exclusion of cost offsets, and inclusion of future unrelated health care costs in extended years of life, did not change the findings that the interventions are cost-effective (AUD 17,000 per DALY and AUD 26,000 per DALY respectively). However, there was a substantial difference between hip and knee replacements where surgeries administered for hips were more cost-effective than for knees.

Conclusions/Significance

Both hip and knee replacements are cost-effective interventions to improve the quality of life of people with osteoarthritis. It was also shown that the dual nature of hip and knee OA should be taken into account to provide more accurate estimation on the cost-effectiveness of hip and knee replacements.     

A comparison of lower-body flexibility, strength, and knee stability between karate athletes and active controls

The purposes of this study were to compare the lower-body flexibility, strength, and knee stability of karate athletes against that of non-karate controls and to determine whether regular karate training results in adaptations that may result in an increased risk for knee injury. Flexibility measurements included knee flexion and extension, hip flexion and extension, hip internal and external rotation, and foot inversion and eversion. Nine karate athletes (4 women and 5 men, age = 24.3 +/- 6.7 years) and 15 active, non-karate controls (7 women and 8 men, age = 22.1 +/- 3.2 years) participated. No subjects reported recent knee surgery or chronic or acute knee pain. Concentric quadriceps and hamstrings strength and endurance were measured using a Biodex II isokinetic dynamometer at 60 degrees .s(-1) and 180 degrees .s(-1). Eccentric strength was measured at 150 degrees .s(-1) and 250 ft-lb (339 N.m). Knee stability was measured via varus and valgus stress and anterior drawer testing. Karate athletes demonstrated a significantly greater right hip flexion (p 相似文献   

Variability,agreement and reliability of MRI knee landmarks

Surface mesh reconstructions of bones are often required to define landmark-based coordinate systems, regions of interest and morphological features when studying the soft tissues of the knee from MRI scans. This study reports the variability, agreement and reliability of osseous landmarks to better understand their downstream effects. Fifteen landmarks were defined on the distal femur and twelve on the proximal tibia. Surface meshes were created from twenty right knee MRI scans with a mean subject age of 30.9 years. A single observer identified landmarks on all twenty knees, while three observers repeated the observations three times on a subset of eight knees. All observations were aligned to the Procrustes mean shapes. Principal component analysis was used to study inter-subject variability and two-way ANOVA for inter- and intra-observer agreement and reliability. Inter-subject landmark variation ranged from 0.6 to 5.26 mm, while inter- and intra-observer agreement were at most 5.1 and 5.69 mm respectively. Between-observer reliability ranged from 0.07 to 0.98 while within-observer values were between 0.51 and 0.98. Landmarks derived from fitted spheres or circles often performed well, while most others had their poorest agreement or greatest variation limited to only one or two cardinal directions.     

Estimation of ACL forces by reproducing knee kinematics between sets of knees: A novel non-invasive methodology

In situ force in the anterior cruciate ligament (ACL) has been quantified both in vitro in response to relatively simple loads by means of robotic technology, as well as in vivo in response to more complex loads by means of force transducers and computational models. However, a methodology has been suggested to indirectly estimate the in situ forces in the ACL in a non-invasive, non-contact manner by reproducing six-degree of freedom (six-DOF) in vivo kinematics on cadaveric knees using a robotic/UFS testing system. Therefore, the objective of this study was to determine the feasibility of this approach. Kinematics from eight porcine knees (source knees) were collected at 30 degrees , 60 degrees , and 90 degrees of flexion in response to: (1) an anterior load of 100 N and (2) a valgus load of 5 N m. The average of each kinematic data set was reproduced on a separate set of eight knees (target knees). The in situ forces in the ACL were determined for both sets of knees and compared. Significant differences (rho<0.05) were found between the source knees and the target knees for all flexion angles in response to an anterior load. However, in response to valgus loads, there was no significant difference between the source knees and the target knees at 30 degrees and 90 degrees of flexion. It was noted that there was a correlation between anterior knee laxity (the distance along the displacement axis from the origin to the beginning of the linear region of the load-displacement curve) and internal-external rotation. These data suggest that in order to obtain reproducible results one needs to first match knees to knees with comparable anterior knee laxity. Thus, an estimate of the in situ forces in the ACL during in vivo activities might be obtainable using this novel methodology.     

Dynamic simulation of tibial tuberosity realignment: model evaluation

This study was performed to evaluate a dynamic multibody model developed to characterize the influence of tibial tuberosity realignment procedures on patellofemoral motion and loading. Computational models were created to represent four knees previously tested at 40°, 60°, and 80° of flexion with the tibial tuberosity in a lateral, medial and anteromedial positions. The experimentally loaded muscles, major ligaments of the knee, and patellar tendon were represented. A repeated measures ANOVA with post-hoc testing was performed at each flexion angle to compare data between the three positions of the tibial tuberosity. Significant experimental trends for decreased patella flexion due to tuberosity anteriorization and a decrease in the lateral contact force due to tuberosity medialization were reproduced computationally. The dynamic multibody modeling technique will allow simulation of function for symptomatic knees to identify optimal surgical treatment methods based on parameters related to knee pathology and pre-operative kinematics.     

Statistical shape modelling reveals large and distinct subchondral bony differences in osteoarthritic knees

Knee osteoarthritis (OA) results in changes such as joint-space narrowing and osteophyte formation. Radiographic classification systems group patients by the presence or absence of these gross anatomical features but are poorly correlated to function. Statistical-shape modelling (SSM) can detect subtle differences in 3D-bone geometry, providing an opportunity for accurate predictive models. The aim of this study was to describe and quantify the main modes of shape variation which distinguish end-stage OA from asymptomatic knees. Seventy-six patients with OA and 77 control participants received a CT of their knee. 3D models of the joint were created by manual segmentation. A template mesh was fitted to all meshes and rigidly aligned resulting in a set of correspondent meshes. Principal Component Analysis (PCA) was performed to create the SSM. Logistic regression was performed on the PCA weights to distinguish morphological features of the two groups. The first 7 modes of the SSM captured >90% shape variation with 6 modes best distinguishing between OA and asymptomatic knees. OA knees displayed sub-chondral bone expansion particularly in the condyles and posterior medial tibial plateau of up to 10 mm. The model classified the two groups with 95% accuracy, 96% sensitivity, 94% specificity, and 97% AUC. There were distinct features which differentiated OA from asymptomatic knees. Further research will elucidate how magnitude and location of shape changes in the knee influence clinical and functional outcomes.     

人工全膝关节置换术50例临床效果观察

目的：探讨人工全膝关节置换术临床效果。方法：选择我院2008年1月至2011年1月收治的行人工全膝关节置换术的患者50例53膝,对其临床资料进行回顾性分析。并作术前、术后HSS评分比较。结果：HSS术后评分,优47膝,占88．7％,良4膝,占7．5％,一般2膝,占3．7％。类风湿性关节炎4例HSS术前评分为35．24±11．78,术后评分为89．61±10．37;骨性关节炎44例HSS术前评分为44．37±10．29,术后评分为91．47±15．65;创伤性关节炎5例HSS术前评分为39．23±11．56。术后评分为90．61±13．2。术前、术后比较差异均有统计学意义（P〈0．05）。术后整体优良率为96．2％。无严重并发症发生。结论：人工全膝关节置换术实施过程中,制订严密的手术计划,拥有高操作技术和理论基础,做好生命体征的密切观察及术后整体的康复功能训练,可取得较好疗效。     

Kinematic motion of the anterior cruciate ligament deficient knee during functionally high and low demanding tasks

The purpose of this study was to determine whether mechanical adaptations were present in patients with anterior cruciate ligament (ACL)-deficient knees during high-demand activities. Twenty-two subjects with unilateral ACL deficiency (11 males and 11 females, 19.6 months after injury) performed five different activities at a comfortable speed (level walking, ascending and descending steps, jogging, jogging to a 90-degree side cutting toward the opposite direction of the tested side). Three-dimensional knee kinematics for the ACL-deficient knees and uninjured contralateral knees were evaluated using the Point Cluster Technique. There was no significant difference in knee flexion angle, but an offset toward the knee in less valgus and more external tibial rotation was observed in the ACL-deficient knee. The tendency was more obvious in high demand motions, and a significant difference was clearly observed in the side cutting motions. These motion patterns, with the knee in less valgus and more external tibial rotation, are proposed to be an adaptive movement to avoid pivot shift dynamically, and reveal evidence in support of a dynamic adaptive motion occurring in ACL-deficient knees.     

Statistical analysis of knee ligament lengths

Absolute locations of the main knee ligamentous structures' insertion sites on the femur, the tibia and the patella have been obtained for 30 knees originating from 18 fresh human cadavers. For each knee, the length of ten selected structures was deduced. These length data form the input of the statistical analysis presented in the paper. The correlations between the ligament lengths are presented. A comparison of the lengths from the left and right (laterality) knees of the same specimen is also done and shows no significant difference. The sex difference is also studied and does not seem to be a determinant parameter for the sample investigated. Prediction equations are proposed to estimate the ligament lengths for the knee in extension with respect to the three external parameters: height, weight and femoral condyle width. The menisco-femoral length, the patellar tendon length and the patellar length are not related to the external parameters and predictions are based on mean values. For the other six ligament lengths, the square multiple correlation coefficient with the external parameters ranges between 0.22 and 0.43. The condylar width is the most often used external parameter in these equations while the weight parameter is never present.     

Evaluation of bone marrow lesion volume as a knee osteoarthritis biomarker - longitudinal relationships with pain and structural changes: data from the Osteoarthritis Initiative

Introduction

Bone marrow lesion (BML) size may be an important imaging biomarker for osteoarthritis-related clinical trials and reducing BML size may be an important therapeutic goal. However, data on the interrelationships between BML size, pain, and structural progression are inconsistent and rarely examined in the same cohort. Therefore, we evaluated the cross-sectional and longitudinal associations of BML volume with knee pain and joint space narrowing (JSN).

Methods

A BML volume assessment was performed on magnetic resonance images of the knee collected at the 24- and 48-month Osteoarthritis Initiative visits from a convenience sample of 404 participants in the progression cohort. During the same visits, knee pain was assessed with WOMAC pain scores and knee radiographs were acquired and scored for JSN. BML volume was summed to generate a total knee volume and an index tibiofemoral compartment volume (compartment with greater baseline JSN). Primary analyses included multiple linear regressions (outcome = pain, predictor = total knee BML volume) and logistic regressions (outcome = JSN, predictor = index tibiofemoral compartment BML volume).

Results

This sample was 49% female with a mean age of 63 (9.2 standard deviation (SD)) years, and 71% had radiographic osteoarthritis in the study knee. Larger baseline BMLs were associated with greater baseline knee pain (P = 0.01), the presence of JSN at baseline (odds ratio (OR) = 1.50, 95% confidence interval (CI) = 1.23 to 1.83), and JSN progression (OR = 1.27, 95%CI = 1.11 to 1.46). Changes in total knee BML volume had a positive association with changes in knee pain severity (P = 0.004) and this association may be driven by knees that were progressing from no or small baseline BMLs to larger BMLs. In contrast, we found no linear positive relationship between BML volume change and JSN progression. Instead, regression of medial tibiofemoral BML volume was associated with JSN progression compared to knees with no or minimal changes in BML volume (OR = 3.36, 95%CI = 1.55 to 7.28). However, follow-up analyses indicated that the association between JSN progression and BML volume change may primarily be influenced by baseline BML volume.

Conclusion

Large baseline BMLs are associated with greater baseline knee pain, the presence of JSN at baseline, and disease progression. Additionally, BML regression is associated with decreased knee pain but not a reduced risk of concurrent JSN progression.     

Morphometric alteration of femoral condyles due to knee osteoarthritis

Aim of this study was to estimate how knee osteoarthritis (OA) affects the shape of femoral condyles by comparing the radiuses of condylar curves between healthy and OA knees. Seventeen female and five male patients with established diagnosis of knee OA were included in the study. Radiuses of medial and lateral condylar curves were calculated from the side view knee X-ray by original mathematical equation and compared to referent values of healthy knees, after adjusting to body height. The average radiuses of condylar curves were between 52.6 +/- 6.2 and 17.6 +/- 3.5 mm medially, and between 43.3 +/- 8.4 and 15.4 +/- 3.7 mm laterally for 0 degrees and 90 degrees femoral flexion contact points, respectively The OA knees had longer curve radiuses medially and laterally at 0 degrees, 10 degrees, and 20 degrees femoral flexion contact points in comparison to the healthy sample (P < 0.001; t-test). Our results suggest that the shape of the femoral condyles in OA knees is changed. It should be aware not only in researching of OA etiology, but also in designing of knee endoprostheses, in a manner to achieve better individual sizing.     

Using three-dimensional kinematics to identify feedback for the Snatch: a case study

This case study evaluated the importance of peak bar velocity and starting posture adopted by a novice weightlifter to the outcome of a Snatch lift. Multiple observations of both successful and unsuccessful attempts were captured using 3D motion analysis (VICON MX: 500 Hz). The following data analysis was then used to derive feedback. In total, 133 attempts of loads ranging from 75 to 100% of 1 repetition maximum (1RM) were performed by the subject (age = 25 years, stature = 171 cm, mass = 74.8 kg, Snatch 1RM = 80 kg). Variables included peak bar velocity, pelvis, hip, knee and ankle joint angles at the starting position for the right side and the difference between (left minus right) sides. No main effects for load, success, or their interactions were found for peak bar velocity. Starting position kinematics were mostly nonsignificant between the outcome of Snatch attempts. Right ankle joint angle was the only exception, where unsuccessful attempts displayed greater (p = 0.0228) dorsiflexion. A more comprehensive finding was achieved through the partition modeling; this analysis provided valuable insight and coaching feedback for the subject in relation to his lower body kinematics at the starting position. Furthermore, the accuracy of this feedback was verified using a holdback data set. Specifically, anterior pelvic tilt (>17.6°) and hip joint (<89.6°) angle were identified as the key features to increasing the likelihood of success. In conclusion, this case study outlines a method of data collection and analysis to assist coaching feedback for an individual.     

Prediction of total knee motion using a three-dimensional computer-graphics model

Twenty-three knees were sectioned, digitized, and standardized to determine the 'average' three-dimensional bony geometry and ligamentous attachments. Data on normal knee motion were obtained from a cadaveric study. An algorithm was written to simulate three-dimensional patella motion. Verification of the knee model was achieved by determining femoro-tibial and patello-femoral contact locations, as well as ligament length patterns, and comparing the results with published data. The criterion for maximum predicted knee motion with a prosthesis in place was the length of the posterior cruciate ligament. Three total knee replacement surfaces were mathematically generated: flat, laxity and conforming. A greater flexion angle was obtained with a flat tibial surface than for the laxity or conforming. Posterior tibial component displacement increased the range of motion, but only slightly. For all tibial surfaces, increased range of motion was achieved with a 10 degrees posterior tilt of the tibial tray. Anterior femoral component displacement increased motion due to reduction in posterior cruciate tension during flexion. The results are applicable to the design and surgical technique of total knee replacement.     

Gait posture estimation using wearable acceleration and gyro sensors

A method for gait analysis using wearable acceleration sensors and gyro sensors is proposed in this work. The volunteers wore sensor units that included a tri-axis acceleration sensor and three single axis gyro sensors. The angular velocity data measured by the gyro sensors were used to estimate the translational acceleration in the gait analysis. The translational acceleration was then subtracted from the acceleration sensor measurements to obtain the gravitational acceleration, giving the orientation of the lower limb segments. Segment orientation along with body measurements were used to obtain the positions of hip, knee, and ankle joints to create stick figure models of the volunteers. This method can measure the three-dimensional positions of joint centers of the hip, knee, and ankle during movement. Experiments were carried out on the normal gait of three healthy volunteers. As a result, the flexion–extension (F–E) and the adduction–abduction (A–A) joint angles of the hips and the flexion–extension (F–E) joint angles of the knees were calculated and compared with a camera motion capture system. The correlation coefficients were above 0.88 for the hip F–E, higher than 0.72 for the hip A–A, better than 0.92 for the knee F–E. A moving stick figure model of each volunteer was created to visually confirm the walking posture. Further, the knee and ankle joint trajectories in the horizontal plane showed that the left and right legs were bilaterally symmetric.     

Coupled motions under compressive load in intact and ACL-deficient knees: a cadaveric study

Knowledge of the coupled motions, which develop under compressive loading of the knee, is useful to determine which degrees of freedom should be included in the study of tibiofemoral contact and also to understand the role of the anterior cruciate ligament (ACL) in coupled motions. The objectives of this study were to measure the coupled motions of the intact knee and ACL-deficient knee under compression and to compare the coupled motions of the ACL-deficient knee with those of the intact knee. Ten intact cadaveric knees were tested by applying a 1600 N compressive load and measuring coupled internal-external and varus-valgus rotations and anterior-posterior and medial-lateral translations at 0 deg, 15 deg, and 30 deg of flexion. Compressive loads were applied along the functional axis of axial rotation, which coincides approximately with the mechanical axis of the tibia. The ACL was excised and the knees were tested again. In the intact knee, the peak coupled motions were 3.8 deg internal rotation at 0 deg flexion changing to -4.9 deg external rotation at 30 deg of flexion, 1.4 deg of varus rotation at 0 deg flexion changing to -1.9 deg valgus rotation at 30 deg of flexion, 1.4 mm of medial translation at 0 deg flexion increasing to 2.3 mm at 30 deg of flexion, and 5.3 mm of anterior translation at 0 deg flexion increasing to 10.2 mm at 30 deg of flexion. All changes in the peak coupled motions from 0 deg to 30 deg flexion were statistically significant (p<0.05). In ACL-deficient knees, there was a strong trend (marginally not significant, p=0.07) toward greater anterior translation (12.7 mm) than that in intact knees (8.0 mm), whereas coupled motions in the other degrees of freedom were comparable. Because the coupled motions in all four degrees of freedom in the intact knee and ACL-deficient knee are sufficiently large to substantially affect the tibiofemoral contact area, all degrees of freedom should be included when either developing mathematical models or designing mechanical testing equipment for study of tibiofemoral contact. The increase in coupled anterior translation in ACL-deficient knees indicates the important role played by the ACL in constraining anterior translation during compressive loading.