At midstance, what moment is occurring at the hip?

During midstance in the gait cycle, the hip is typically in a position where it is experiencing an extension moment. As the body weight shifts over the supporting leg, the hip joint is stabilized in extension due to the action of the hip extensors, primarily the gluteus maximus and hamstrings, which contract to maintain this position.

This extension moment is crucial for forward progression and support, allowing the body to transition through that phase of gait without collapsing. The pelvis is also moving forward, and as such, forces are directed posteriorly through the hip joint, leading to this extension moment.

In contrast, the other options refer to different motions or moments that might occur at other phases of gait. For example, a flexion moment would be more applicable during initial contact or loading response when the hip is flexing to absorb the forces of impact. Adduction moments are more associated with stabilization while the body is in dynamic motion or during late stance as the opposite leg prepares for swing. Internal rotation moments can occur during the swing phase when the hip reorients, but they are not significant during midstance. Thus, understanding the timing and mechanics of the gait cycle helps clarify why the extension moment is particularly relevant at midstance.