I posted a thread about exactly the same thing about a month ago. I have cut down practising for the time being and the injury is slowly getting better. In my case, the doctor thinks that tension in the neck/back/shoulders led to a muscle being too short. When it couldn't expand further, I put the tendon out. (I'm completely ignorant on all matters medical - so doubtless another 'Catter will put it better). I can play again now, but I have to do more about the root problem, which is further up. Good luck to you. Tell us how you are getting on. Alan.