I've had trouble with a little muscle above the back of my left hip. It's been going on and on for months and I keep trying to stretch it out and strengthen it.
My massage therapist observed that my body sometimes is twisted. Not up one side but more twisted on its' axis. The right side seems to want to be further forward than the left. She suggested I see my chiropractor. He confirmed. He said that the left hip is hurting because the right side is weaker and it puts more work on the left. "Strengthen that right side more," was his advice.
If I lay off asana for a bit, the hip hurts less. The more asana I do, the more it hurts and ends up not just hurting for a while and fading, but it will then start just hurting all the time. And so I keep doing poses and stretches designed to bring more right/left balance to my body.
Then suddenly last night, as we lay in svasana, I had an SBI (scathingly brilliant idea)! I realized that, in asana, I tend to allow the left-ward stretching to go further because that side is stronger! I need to push more on the right but also to back off a little more on the left.
I can be so slow sometimes.