I am more interested in the nerve and its relationship to the piriformis muscle. The size of the muscle can vary a lot and it is not possible to accurately and reproducibly measure the muscle size or volume with ultrasound. I am concentrating on the nerve looking for it passing through or over the muscle (remembering there are 2 components to th sciatic nerve and one may pass beneath and the other through or over etc) and also looking for neural oedema compared to the other side. I also test for a tinnels sign with transducer pressure.
Steve.