My joints are also deteriorating. However, my doctors don't want to touch it until they absolutely have to. This being when it gets really bad and I can't live with it anymore. I've learnt over the years that it's best to treat the pain, not necessarily the jaw. Hence the reason I would leave it be if there was no pain.
An MRI would be the best way to see what's going on in there, just be wary of what treatments are recommended and always try conservative, reversible and non-invasive treatments first.
Good luck and I hope you remain pain free.
Melanie.