Suggest Remedy For Pain On Legs After Taking Prednizone

I have been on prednizone since JUne for what drs thought wa PMT with no relief form pain in legs at all...went to muscle doc at Uivers of MIami and he upped dosage to 50 mg/ day for 2 weeks and that did nothing either. AM cutting to 40 on his orders in two days and then will wean from prednizone...but what else could cause a lifelong athlete of 74 to suddenly be so weak although doc says my egs are strong and tmany tests show only low eve vitamin d and inflamation in joints?