It only happens when I've been sitting or laying still. Also, it wakes me up in the middle of the night. It takes all my might to start moving that joint again. I can't just move it...I have to use another arm to move it! It is very painful. Any clues. I am 37. I am somewhat malnourished (not too bad though). I've been eating well for the past week. I'm 5'1 and 100 pounds. I don't think that could be it. I tried looking on the internet but with no success. Any ideas? Of course I will be seeing a doctor...just asking until then> Thanks