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Purpose: Although various kinematic measurements with advanced technology have been used for quantitative evaluation of the pivot shift test, there is no clinically available quantification method of the pivot shift test. The purpose was to describe a novel image analysis technique for quantitative assessment of the pivot shift test using universally available and affordable devices., Methods: Five ACL deficient knees were tested during examination under anesthesia. Three skin markers were attached to bony landmarks on the lateral side of the knee joint, (1) Gerdy's tubercle, (2) fibular head, and (3) lateral epicondyle. A standard digital video camera captured motion of the lateral aspect of the knee during the pivot shift test. The image was processed into a 2-dimensional (2-D) coordinate system with Image J software (National Institute of Health, USA) to trace the three landmarks. The anteroposterior (AP) position of the femur was calculated on consecutive still images extracted from the video recording. AP translation over time was reported., Results: The reduction phase of the pivot shift could be tracked consistently by a sudden anterior translation of the distal femur. The sudden anterior translation of the lateral epicondyle was on average 3.7 ± 2.1 mm and occurred within 0.2 ± 0.1 s from the start of this anterior translation till the end., Conclusion: The sudden shift of the lateral compartment of the knee joint was successfully detected by this newly developed image analysis measurement method. This image analysis technique facilitates a simple and affordable method to evaluate the lateral pivot shift test., Level of Evidence: Diagnostic studies, Level IV.

Study Design: Two-factor, mixed experimental design., Objectives: To compare movement patterns of subjects who are anterior cruciate ligament (ACL) deficient and classified as noncopers to controls during early stance of anticipated and unanticipated straight and cutting tasks., Background: Altered neuromuscular control of subjects that are ACL deficient and noncoper theoretically influences movement patterns during unanticipated tasks., Methods and Measures: The study included 16 subjects who are ACL deficient, classified as noncopers, and 20 healthy controls. Data were collected using an Optotrak Motion Analysis System and force plate integrated with Motion Monitor Software to generate knee joint angles, moments, and power. Each testing session included anticipated tasks, straight walking task (ST), and 45 degrees side-step cutting tasks (SSC), followed by a set of unexpected straight walking (STU) and unexpected sidestep cutting (SSCU) tasks in a random order. For all tasks speed was maintained at 2 m/s. Peak knee angle, moment, and power variables during early stance were compared using 2-way mixed-effects ANOVA models., Results: For both the straight and sidestep tasks, the noncoper group did not show a dependence on whether the task was anticipated or unanticipated (group-by-condition interaction) for the knee angle (straight, P = .067; side-step cutting, P = .103), moment (straight, P = .079; side-step cutting, P = .996), and powers (straight, P = .181; side-step cutting, P = .183) during the loading response phase. However, during both straight and side-step cutting tasks, the subjects in the noncoper group used significantly lower knee flexion angles (straight, P = .002; side-step cutting, P = .019), knee moments (straight, P = .005; side-step cutting, P < .001), and knee powers (straight, P = .013; side-step cutting, P <.001)., Conclusions: This study suggests subjects that are ACL deficient and classified as noncopers use a common abnormal movement pattern of lower knee extensor loading even during unanticipated tasks.

Introduction: The quadriceps avoidance gait pattern may not be as common in ACL deficient (ACLd) gait as previously described., Purpose: The purpose of this study was to investigate the existence of the quadriceps avoidance pattern in ACL deficient patients and to further identify gait compensations that may exist in this subject pool., Methods: In the present study, hip, knee, and ankle gait kinematics, and kinetics and thigh EMG profiles were recorded and compared for 16 ACLd and 8 control subjects., Results: The quadriceps avoidance gait pattern was not observed for any of the subjects. Hip, knee, and ankle kinematics and kinetics were not different between groups. However, nine ACLd subjects (group A) demonstrated a normal biphasic knee moment pattern, whereas seven (group B) demonstrated an all knee extensor pattern. This indicates different adaptive mechanisms may be present in ACLd gait. Group A exhibited a hip strategy that increased hip extensor output, decreased knee extensor output, and allowed normal knee kinematics. Group B demonstrated a knee strategy that increased the stiffness of the joint and utilized a flexed knee gait., Conclusion: The prevalence of multiple adaptive strategies to compensate for ACL deficiency has several important ramifications. First, an ACLd subject pool with mixed compensating strategies may deter the identification of specific coping mechanisms and account for the confounding results in the literature. Second, the importance of the hip extensors should not be overlooked when studying this population.