"We are doing a pelvic / thoracic study with our players. The primary tester has measured subjects hip ROM prone and I know we do most of ours seated. Could you enlighten me on the differences as there is some debate. I know the capsule is tensioned differently and the tissue compression seated is different than prone but wanted to get your take."
You obviously can test rotation in either position and will more than likely arrive at the same values if the hip capsule is in a position of true rest or neutrality with respect to all three planes. When the hip is in an anatomical prone position, ER is accompanied by anterior glide of the femoral head. Rotation is limited by tension in the anterior capsule and the pubofemoral ligament. Since most ligaments are more loose in the seated position, I personally like testing in this position. ER is now accompanied by a superior glide of the femoral head and rotation is limited by the superior capsule and the iliofemoral ligament. Since I like to look at the ilium position in general , this position is more reflective of iliofemoral restriction and pathology if it exists. IR is accompanied by a posterior glide of the femoral head when in prone and tension in the posterior capsule and tension of the ischiofemoral ligament limits IR. IR is accompanied by an inferior glide of the femoral head and is limited by tension in the inferior capsule and the superior ischiofemoral ligament in the seated position, which makes me more likely to look at in this position because of the influence of the inferior capsule, not the posterior capsule seen with the prone position. The inferior capsule restriction indicates that the individual I am testing may need more level 4 or 5 squatting to get the IR needed if indeed the restriction is an inferior versus a posterior capsule limitation. If IR is more restricted when in the prone position, than I would implement a posterior capsule stretch type of program to compliment concurrent active IR.