My Corgi Has Tremors In His Hind Legs, Like He Is Shaking With Cold. Any Ideas As To What This Is?

I have a male Pembroke Corgi that is doing the same thing.  It started on one side and happened very seldom now is on both sides and happens everyday.  A Corgi owner that I met in the park said it was the beginning of hip displaysia and to get it xrayed.  She said the same thing happened to her Corgi and they prescribed Rimidal (sp?)