He's working on a friend of mine now on a different issue. I noticed that friend never went on the balls of his toes which is what we need to do quite often in Standard. When I asked him to walk on his toes, he literally could not. His feet rolled out and only with much effort and strain could he force himself onto the balls of his feet. Mesrop diagnosed him with an overactive piriformis muscle which caused the external rotation, and along with that, corresponding weak glutes. He now has a program to strenghthen and activate his glutes. Someone else misdiagnosed him with weak ankles, but the problem originates much higher up.
The more I learn about bio-mechanics the more I become painfully aware that many things our dance teachers try to get us to do may be physically impossible at the time and may require exercises and stretches to bring our bodies back into bio-mechanical harmony. Doing so will not only get or keep us out of pain, but greatly improve our dancing.