Tibiofemoral Shear Forces During Isokinetic Knee Flexion

Publication Date


Type of Culminating Activity


Degree Title

Master of Science



Major Advisor

Ross E. Vaughn


This study addresses the question of whether anterior shearing forces are present at the knee during isokinetic knee flexion. It further investigates whether these forces are significantly different when resistance is proximal on the tibia as compared to distal, and whether the forces differ between an anterior cruciate ligament deficient knee and a "normal" knee.

Ten subjects, each with one ACL-deficient knee, were tested on an isokinetic dynamometer while being video taped. They performed standard isokinetic testing on both legs at 60° per second, once with resistance placed proximally and once with distal placement. Torque readouts were utilized, along with measurements taken from the subjects, to calculate the forces acting at the knee. Video recordings were digitized utilizing a Peak2D system, yielding linear and angular displacement, velocity and acceleration data.

Results of the study showed that for all subjects there was anterior shear at the knee during the first 10-15° of knee flexion. significant differences between pad placements were found at 15° and 30°. There was no significant difference between ACL-deficient and "normal" legs. The findings are significant for clinicians who are involved in knee rehabilitation, and who use isokinetic exercise for postsurgical or postinjury ACL patients, as knee flexion is routinely used in ACL protocols post-surgically and/or postinjury. The anteriorly directed shear forces present in this study could cause undue stress and strain, or damage to a vulnerable knee.

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