I too have Hashi's/hypothyroid, and when this all started getting bad and rearing it's ugly head, [about 7 years ago], I started getting some serious pain in my right thigh and it was later diagnosed to be tendonitis. It hurt almost all of the time. So a couple of years later when I was dx'd with the thyroid problem, and after I'd been on meds [for me it took a while] and got my levels in a pretty good place, that pain started going away.
Today, my levels are good, I feel great, and that pain is totally gone. It does return when my levels are "off"....hyPO *or* hyPER, but it's been a while. Lots of ugly symptoms went away.
Yes...I believe that my tendonitis was caused by my thyroid being off. Once your levels get to your good spot, and you have some time to heal, you too will feel a lot better. I never thought the day would come, but it did, [thank God], and life is good again.
My best to you and everyone else on this board..