I have had 8 surgeries on my left knee, and I can honesstly say that taking glucosamine, chondrointin, and msm has helped with the pain in my knee. I stopped taking them after my last surgery and my shoulder started hurting, started back taking them and the pain in my shoulder is slowly going away. So yes, i do think they work, but everyone is different in that matter. If your shoulder is hurting that bad, then you should see a doctor to make shure you haven't really fucked it up. You could also try doing some rotator cuff exercises, those will really help it its the rotator cuff that is the problem.