Hip flexibility potential - ligaments or muscles?

Our user asked: "Hello, I am interested to know if there is a way to test one's flexibility potential for external rotation of the hips. In other words, I'm wondering whether one can determine if an individual's hip tightness is due to muscles -- which can thus be lengthened through stretching -- or if it's due to ligaments, which cannot/should not be stretched. I have seen links about how to determine range of motion, but not for flexibility potential. I would greatly appreciate any information you can give me!"

Ask a PT Response: "Testing for piriformis flexibility can be performed both in supine or prone. The link provided shows a therapist assessing the piriformis in supine  http://www.exrx.net/Testing/FlexFunction/LyingPiriformis.html  . Both sides are assessed and compared to one another. A goniometer can also be utilized to allow for objective measurements. Normal ROM for Hip IR is 0-40degres and Hip ER 0-50degrees. Joint play assessment at the hip joint by the therapist would also allow for a better understanding of any restrictions at the hip joint as well."