Having enough stable internal hip rotation is just as important as having enough external rotation. Lack of sufficient internal rotation is a real problem during gait and in athletes. This deficit can wreak havoc on the entire kinetic chain. What doesn't occur or what doesn't get buffered in the hips plays out in the knee or in the pelvis.
Don't forget that there are many important internal hip rotators that need your clinical eye on assessment: the vastus lateralis, anterior bundle of the g.medius and g.minimus, TFL to name a few. If you have difficulties visualizing how these muscles drive internal rotation you are not looking at the model from the foot fixated on the ground, you are still seeing things from an open kinetic chain perspective. Just remember, it is even more complicated than that, we are constantly moving through cycles of stability and mobility, with all muscles crossing a joint providing cylindrical give and take (concentric-iso-eccentrical) mobility while at the same time providing adequate stability control through safe joint centration. It is a symphony of events.
Here today, these thoughts were triggered when we came across an old (1998) article on components driving internal rotation in cerebral palsy. In this case, driving too much rotation.
Treatment of internal rotation gait due to gluteus medius and minimus overactivity in cerebral palsy: anatomical rationale of a new surgical procedure and preliminary results in twelve hips.
Joseph B. Clin Anat. 1998. Treatment of internal rotation gait due to gluteus medius and minimus over-activity in cerebral palsy: anatomical rationale of a new surgical procedure and preliminary results in twelve hips.