I've fought tennis elbow in my bow arm elbow, and am now fighting tendonitis in my string arm shoulder. Have been under the care of both doctors and physical therapists in both cases. In neither case have any muscles or tendons had major tears, but micro-tearing in both muscles and tendons that hasn't repaired itself has been a part of the problem. Micro-tearing is a normal part of any sports activity, and is a part of muscle development, but the body isn't as good at repairing itself as we age. When a muscle or tendon tries to repair itself and can't, calcium deposits may accumulate instead. Over time, these calcium deposits can solidify and lead to arthritis or chronic tendonitis.
Contrary to what one might think, doctors and physical therapists do not recommend inactivity, except for a few days at the onset to see if it might be a transitory pain that goes away on its own. But if the condition is chronic, inactivity can lead to further calcification and atrophy, making the condition worse. Of course, just continuing the activity that caused the problem in the first place can make the condition worse too. What is needed are exercises that promote blood flow to the affected area and healing.
I had ultrasound treatments from physical therapists when I had tennis elbow, and also more recently when I had shoulder problems. The ultrasound helps break up the calcium deposits so that they can be removed by the blood. The correct kinds of exercise also promote blood flow to the injury that can promote healing and prevent atrophy. This generally means many reps at slow speed of low stress exercises specifically aimed at the area involved. For tennis elbow, I recommend the Theraband flexbar, which you can find on Amazon.
My recent shoulder problem was aggravated by an accumulation of calcium in a tendon that had to slide under some other part of my shoulder when I drew the bow. It was very painful, and at one point I couldn't raise my right arm any higher than my hip. The accumulation of calcium may have been caused by the repetitive motion of drawing the bow many thousands of times causing many microtears that didn't fully repair themselves. This is a very common problem, and if you look on the internet you will find many examples of it caused by things other than pulling the bow. Fortunately, if you do the right exercises without doing things that further aggravate it, the calcium deposits will start to dissolve and the inflammation will go away.
The main reason for seeing an orthopedic surgeon was to see if I had a major tear that would require surgery, which fortunately I didn't. The orthopedic surgeon said that if I just drew the bow at waist level, I could probably go on shooting for the rest of my life without any further problems (remember, I’m 74, so that statement doesn't have the same meaning as it would if you said it to someone who was 40). We both sort of chuckled at that, because we both knew I couldn't hit anything if I shot that way. But it got me to thinking about how I was drawing the bow, which was pretty much a straight back pull, with my elbow out at 90*. So I experimented around and rewatched Arne's video on the rotational draw, and tried drawing more out to the side with my elbow pulling somewhat down, and then raising my elbow at full draw and coming in to my face from below and the side. I end up in the same place, but it doesn't hurt. I showed it to the orthopedic surgeon, and he thought it was a great idea that he would remember if anyone else came to him with that problem.
I have cut back to shooting every other day rather than every day, so my body has a better chance of healing itself. Of course, there go my chances of winning the Trad Worlds (ha ha), but at least it looks like I can continue to shoot. I'm supposed to do the exercises for the rest of my life, which is harder to do now that my shoulder doesn't hurt anymore, because they are boring, but better than shoulder pain.