Figure 45. Schematic demonstrating the effect of differences in the degree of hip and knee flexion on the joint forces experienced by the femur.

This is illustrated with right lateral views of a human (A) and a typical bird (B) in approximate mid-stance postures. In the more flexed posture of birds, the hip joint force is more anteriorly oriented relative to the long-axis of the femur (dotted line) compared to humans. Further, the knee joint force is more posteriorly oriented relative to the long-axis of the femur compared to humans.