I'm also not 100% sure what you're getting at. Like many of my fellow posters above say, there are definitely medications in place for various non-structural MSK diseases, although maybe to varying degrees of efficacy. I think there is also ongoing research, since we are getting some new drugs--Forteo and Olumiant are the first that come to mind.
I know that there's conflicting evidence when it comes to efficacy of corticosteroid shots for arthritic patients. Also, there's those hyaluronic acid injections--I want to say the verdict on those is that they really don't work, but I'm also pretty sure some doctors still administer them. There are also some more niche joint injections for people with arthritis that I can't remember off the top of my head, but I know the jury's still out on those because they're pretty new.
So, I mean, OP, if you're looking for research topics, those might be good ones? I think there's already research going on about the various injections and how effective they really are, but still, you might be able to find a new research question or something.