Ankle, feet and hand weakness

I have a problem that I haven't quite figured out.  I have weakness in my hands/fingers and feet/ankles.  The feet and ankles are the biggest problems.  My knees and hips will give at times as well but even if things don't hurt they feel weak like they could give out and the longer I walk continuosly the harder it gets to continue to walk, as though my joints are stiffining up and getting weaker at the same time.  I've gone from walking as fast as some people run to being out paced by someone using a cane at times, all in a 6 month period (it's been a steady downhill run).  I really noticed the weakness when I took a dose pack of prednisone starting at 30mgs.  The 30 and 25mg days pretty much wiped out pain and stiffness, but my feet and ankles felt extra weak.  Sorry for the sort of rambling message, any ideas as to what is going on would be appreciated.