I'm not sure about their therapeutic use. One thing concerns me--I sometimes see them labeled as a "protein supplement." Technically true, but collagen is the one incomplete protein from an animal source that's readily available, it lacks tryptophan. A protein shake diet popular in the 70s resulted in a number of deaths, likely due to reliance on collagen as a sole protein source. It's fine (at least, it's safe) as a supplement--but shouldn't really be counted towards your protein requirement.