Anyway, he suggests that lack of internal (medial) hip rotation is a contributory factor in low back pain experienced by golfers and tennis players. Actually he refers to an imbalance in hip rotation rather than limited rotation in one direction. He says:
In one study, 48% of subjects with low back pain (LBP) had increased lateral rotation and a deficit in medial rotation of the hip (Ellison, JB).
Another interesting point he makes was that:
Researchers found that a statistically significant correlation was observed between a history of LBP and decreased lead hip internal rotation (Vad, Journal of Sports Medicine).
The obvious thing might be to assume that the limited medial rotation come from tight lateral rotators, and that can certainly be true. But don't ignore the possibility that it might be that the medial rotators are not engaging properly. I've certainly seen that with at least one recent client where medial rotation wasn't restricted, it just didn't happen readily.