Gender differences in knee angle when landing from a drop-jump

Twenty (10 men and 10 women) healthy, height-matched patients (mean patient age: 28+/-5 years) participated in a study testing the (null) hypothesis that no significant gender differences would be found in the knee flexion angle upon impact from a drop-landing. Patients performed three unconstrained jumps from three vertical heights (20, 40, and 60 cm) onto a concrete floor. Reflective markers were placed on the right side of the body at six sites: the head of the fifth metatarsal, the lateral malleolus, the lateral femoral condyle, the greater trochanter, the posterosuperior iliac spine, and the anterosuperior iliac spine. Ankle, knee, and hip angles in the sagittal plane were then measured at 120 Hz using a two-dimensional motion analysis system. Significant gender differences in knee flexion angles were found at ground impact during the drop-landing (P<.05). The largest gender difference in knee angle occurred when landing from a height of 60 cm: men landed with 16 degrees of knee flexion, whereas women landed with a significantly straighter knee flexion angle of 7 degrees (P<.05). A similar gender difference was found when landing from the medium jump height (40 cm). In this sample, women landed with a straighter knee than did age- and height-matched men.