Hello Whirlwind, You asked if MG is responsible for your joint pain. I wish we could answer your question. Finding a cause is often a process of elimination. So, for example, a visit to a Rheumatologist might shed some light on a cause. Myasthenics can be targets for other autoimmune/inflammatory disease.

There most certainly can be pain with myasthenia. Pain in the
shoulders and neck, which hold up the head, is one example, as well as
pain in the hips from perhaps, an unsteady gait.

Pain is in a sub-category. In other words, it's not a classic, or hallmark
symptom. Hallmark symptoms are a generalization, and so we have to try not to be angry at physicians who say there isn't pain with MG--they are, for the most part, talking about classic symptoms. However, they would be wise not to wave it off either.

Anything unusual to you, must be investigated.