I have supraspinatus tendonosis and am told biceps tendon and bursa implicated as well. For years I have slept on my stomach hugging one pillow in each arm and angling my head down. Now, with this injury I try to sleep on my back but can’t. I assume that it is bad to sleep on my stomach with my arms up, but honestly, its more comfortable than on my “good” side which hurts my ‘bad’ shoulder – guess I need a pillow under that arm. And oddly, snuggling up on my ‘bad’ side, with shoulder against the underneath-pillow, isn’t bad at all.