Differences in lower extremity kinematics between a bilateral drop-vertical jump and a single-leg step-down

STUDY DESIGN: Mixed-model, repeated-measures design in a laboratory setting. OBJECTIVES: To examine the differences in hip, knee, and ankle kinematics between a bilateral drop-vertical jump and single-leg step-down. A secondary purpose was to examine gender differences in kinematics of the tasks. BACKGROUND: Both a drop-vertical jump and step-down task have been used to evaluate lower extremity movement and injury risk. The differences in joint angles between these tasks have not been reported. METHODS AND MEASURES: Three-dimensional joint angles of the hip, knee, and ankle of 19 females and 18 males were evaluated with a high-speed camera system while the subjects performed a bilateral drop-vertical jump and a single-leg step-down. Maximum joint angles were compared between tasks and genders using ANOVA models. RESULTS: When averaged across both genders, the step-down produced greater rearfoot eversion (12 degrees compared to 8 degrees) (P <.0005) and hip addluction (16 degrees compared to 1 degrees) (P =.03) than the drop-vertical jump. Females had greater hip internal rotation in the step-down than in the drop-vertical jump (5 degrees compared to 2 degrees) (P =.02). When averaged across both tasks, females had greater knee abduction than males in both tasks (4 degrees compared to 0 degrees) (P <.0005). CONCLUSIONS: The unilateral step-down task produced greater motion in the frontal and transverse planes at the ankle and hip, and would be appropriate in evaluating control of the hip. The bilateral drop-vertical jump produced greater knee abduction in both genders and may be appropriate for evaluating excessive knee abduction as a risk factor for noncontact anterior cruciate ligament injury, for example. The 2 tasks appear to challenge the neuromuscular system in different manners, and both should continue to be used in the investigation of injury risk.