I have this ache in my left arm. i feel it in the muscles in front and behind the arm down to my elbow. It is excruciating if i extend my arm backwards (like getting something off the back seat of a car while in the front seat). It is a dull ache otherwise. I first noticed it in March. It has gotten really uncomfortable to sleep on my stomach. I think i hear some sort of creeky sound in my actual shoulder. Just don t know. otherwise i am in pretty good shape. i am 62 - a woman - and in pretty good shape otherwise.