Figure 1.

The external hip- and knee-adduction moments are influenced by the lever-arm distance from which the ground reaction force passes medial to the joint center. A, Neutral pelvic alignment during gait is illustrated. The free-body diagram is provided for simplicity using a quasistatic approach. B, However, increasing pelvic drop potentially could increase the length of the ground reaction force lever arm at the hip and knee, subsequently increasing the external-adduction moments at both joints.