Tight shoulder muscles for almost a year?

Stretch?: With the information given, the first suggestion is stretching. You can use a broom handle and your good arm to push the stiff shoulder to a comfortable limit and hold it. You can also use the hand on the bad side to crawl up a nearby wall to that same comfortable limit. If you are really stiff, a physical therapist may help. Failing this see your primary provider or a sports specialist.