Hi Alan,
Welcome! Muscle fatigue is a definite symptom. I've not had any pain in my knees, but some in my feet. I think it is unrelated to my MG though - I think I just am starting to get some arthritis (I'm only 29, but my family has a lot of arthtitis in it). My muscles get sore sometimes if I over do things and I get bad muscle cramps (I think that is related to my steriod prescription and the related minerals they absorb - potassium and calcium). The double vision is annoying eh? I was doing some archery on the weekend and I was really worried that I was going to end up really hurting the sheep who were quietly grazing in the field behind the targets. Thankfully all survived (I even managed to hit the centre of the target.... once).

Hope that helps a bit.. no real information for you, but sometimes it is nice to hear about someone elses experiences!
~Kathy