If I sleep too long in the same position, I wake up in horrible, horrific hip joint pain. (It has happened to me with my arm/shoulder when I sleep too long with my arm over my head. But it is far more prevalent with my right hip.) I've had an x-ray done in the past but no issues. After researching and talking to my doctor, I believe it's just what I said: sleeping too long in 1 position + age + all the activity I have done over my lifetime that my body is now "complaining" about. LOL. So far I've found no magical fix for it, other than moving around and stretching my hip joint as much as I can stand. Good luck, ladies!