You should work with a very good massage therapist. A lot of tendinitis is actually rooted in highly muscles surrounding the tendon.
I had petellar tendinitis in the knee, got my quad lossened after a few session and I’m all good.
Same with elbow, tight forearm or bicep, triceps heads can cause them not to take the load they are suppose to. Forcing your tendons and other muscles to to compensate and take more load then they are made for. Also helps hand pain and numbness and weakness. Something can be pushing on your nerves being to tight.
Chronic tendinitis is also always cause by the muscles surrounding your tendon not functioning 100%