Yes, I have been having tendonitis and various muscle/ tendon pain and injuries from Long Covid too, among many other symptoms. Post exertional malaise, autonomic nervous system dysfunction with tachycardia with minimal movement kept me from doing any kind of exercise. Initially I could barely walk around at all. I eventually could do slow paced short walks but nothing else and noticed muscle wasting with fat gain. Eventually I began to be able to do more butI kept getting over use tendon pain with small activity snd muscle aches. Once when pulling on a car seat adjustment bar I heard a pop and suffered rib separation. Prolonged standing resulted in gluteal tendonitis. Diffuse muscle pain and tendon pain has been common,
The thing that has helped me most was going on the antiviral drug , valacyclovir that I ran across when taking it for a cold sore noticed that the two doses helped me feel better. I had been taking 1gm twice a day until a trial off for a little over a week when the gluteal tendonitis ( made sleeping impossible) occurred and a flare of fibromyalgia like diffuse muscle and tendon pain and maybe joint pain too came during the time off. Within a few hours of starting back with a 2 gm dose of Valacyclovir the gluteal pain vanished and muscles improved. Continuing with the anti viral. Also take fish oil, co Q10, and Nattokinase, Magnesium glycinate and vitamin D and C.