I agree that this sounds like a referred pain issue. Could be the pelvis or could be the lumbar spine. Also could be the attachment of quadratus lumborum from the waist down onto the pelvis. Pain in this region is common on palpation with these types of issues but less so on simple leg rotation (I am thinking this was inwards?).

Lying down symmetrically on your back and get someone to check the apparent length of your legs and let is know if they are the same (check from the bumps or malleoli on the inside of the ankles for reference). Then also check on the anterior superior iliac spines on the front of the pelvis (again the bumps on the front of your pelvis) to see if they are also level or not. Also then stand on one leg vs. the other and tell us if either provokes symptoms.

Look fwd to your answers