I had shoulder problems for years and had it worked on quite a bit. After the last go around from a 6 hour mtn bike ride, they did a full spinal exam and a dye injection MRI on the shoulder and it turns out I have scoliosis. Shoulder socket was basically fine. The muscles were getting so tight in my neck and spine it was pulling my shoulder over the socket and causing all the pain. I'm still having problems on my right side so I'm starting some pilates and yoga to work on my back and neck. I can't do any road rides over an hour or so without being in a bunch of pain. Mtn biking is slightly better since you move around more. If the pain is consistent and you've used the same set up for quite a while, I'd have your neck and back looked at.