I have used TB500 for nagging pains in the shoulder and elbow which worked great (and I will contradict myself in just a minute). But it works fantastic and the stamina/endurance boost is a nice plus. I have known people (in real life and online) that have used to for attempting to heal injuries like RC, labrum, ruptured distel tendon, etc... but not with good results.
Don't hold me to this, but I suspect that for muscles - it works the best but for injuries and pains that are due to ligaments, tendons, or joints the effects are limited and hardly noticeable.
I think the reason that I had good results with the shoulder and elbow is simply because I caught it in the early stages and combined it with rest as well.
Look at it this way.... can't hurt to try can it? It's cheap enough.