I Am Having Tightness In My Upper Legs; Sometime In

I am having tightness in my upper legs; sometime in hips but not usually. It is worse if I sit too long. I have it basically all of the time, sometimes more painful than other times. It hurts when walking and it affects my balance on the treadmill. I'm just trying to figure out what it is and what I can do. I went to PT for awhile but it only had temporary improvement.