Date of Paper/Work


Type of Paper/Work

Research Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Advisor

Jaynie Bjornaraa


BACKGROUND AND PURPOSE: Injuries to the anterior cruciate ligament (ACL) are common among both male and female athletes. Both the female gender and fatigue have been demonstrated to increase injury rates. This research aims to reconcile the movement pattern and fatigue protocol with what is seen in sport, while including both men and women to see differences between knee biomechanics. The research will compare the lower extremity biomechanics of a jump-land (double and single leg) between healthy men and women after a sports specific fatigue protocol. Ultimately, this research is intended to examine movement patterns which may predispose the subject to ACL injury.

METHODS: Twenty healthy subjects were studied (26.3 ± 3.5 years old), 10 of which were female. A 3D electromagnetic system measured knee kinematics and kinetics during 3 jumping tasks. The subjects completed 4 sets of 3 different, randomized jumps (bilateral to bilateral, bilateral to single-leg right, and bilateral to single-leg left) on force plates. The subjects completed a fatigue protocol consisting of jumping, sprinting, step-ups, and an agility ladder and were immediately re-assessed by completing the 3 different jumps. A paired t-test was used to analyze pre and post fatigue and a one-way ANOVA was used for analyzing gender comparisons for each variable.

RESULTS: Significant differences were found between pre-fatigue and post-fatigue internal rotation and adduction knee angles for all 3 landings; other angles and knee moments were significantly different dependent on type of landing. When comparing gender for each variable, internal adduction moments and ground reaction forces were significantly different for all landings. Knee angles were also significantly different dependent on type of landing and dependent variable. Finally, females demonstrated greater biomechanical changes in landing mechanics post-fatigue than males.

CONCLUSION: The results support previous literature that fatigue and gender have an impact on jump and land movement patterns at the knee. The differences in knee angles and moments from the current study, as seen by internal adduction moments and ground reaction forces, demonstrate that fatigue and the female gender are risk factors for ACL injury. This may support the current pattern of greater ACL injuries in female athletes, especially when doing a jump-land movement.