Effects of a combined inversion and plantarflexion surface on knee and hip kinematics during landing

Although landing in a plantarflexion and inversion position is a well-known characteristic of lateral ankle sprains, the associated kinematics of the knee and hip is largely unknown. Therefore, the purpose of this study was to examine the changes in knee and hip kinematics during landings on an altered landing surface of combined plantarflexion and inversion. Participants performed five drop landings from 30cm onto a trapdoor platform in three different conditions: flat landing surface, 25 degrees inversion, or a combined 25 degrees plantarflexion and 25 degrees inversion. Kinematic data were collected using a seven camera motion capture system. A 2x3 (legxsurface) repeated measures ANOVA was used for statistical analysis. The combined surface showed decreased knee and hip flexion range of motion (ROM) and increased knee abduction ROM (p<0.05). The altered landing surface creates a stiff landing pattern where reductions in sagittal plane motion are transferred to the frontal plane, resulting in increased knee abduction. A stiff landing pattern is frequently related to increased risk of anterior cruciate ligament injury. It may be beneficial for athletes at risk to train for alternate methods of increasing their sagittal plane motion of the knee and hip with active knee or trunk flexion.