15yr old son, in puberty-grown 7 inches in last 10 months; when puberty began, he experienced upper arm pain-below the shoulder, where the bicep and tricep connect…rest, ice, motrin. Fine after a few weeks. Now it’s back, sometimes radiates down the arm a bit. He hasn’t thrown in 2 weeks but he’s been playing basketball (similar motion?) Thinking it’s tendonitis…thougths?
Go and see a sports doc, that’s the only way you’ll ever know what’s going on in your son’s shoulder.
You don’t want to get advice from a message board over what the possibilities could be. Get it looked at by a qualified medical physician.