One of the benefits of being a member of the Musicians Union (that's here in the UK) is that they have medical contacts. I had a problem with the upper joints in my index fingers (both hands) which were affecting my guitar playing, and having consulted my own doctor was able through the MU to be referred to their consultant in Harley Street. Who knew all about playing instruments and all that stuff, and who eventually referred me on to my local hospital where I had some treatment using magnetic imaging (if I remember rightly) and some massage, and the problem has not recurred.
So I'd thoroughly recommend any UK 'Catters with joint problems that affect their music to take advantage of their membership of the MU (because of course you're sensible enough to be members ...aren't you?) and get some specialist help!

Anne