I have a 5 year old Buckskin/Quarter mare who has had some intermitent lameness over the past year. She is traveling very oddly in the rear with her right rear leg swinging so far inside she is almost traveling diagonally. The front is traveling straight but she is paddling with both front feet. She has been thoroughly tested with no diagnosis. She has had a full body bone scan with a nuclear injection and the only concentration of isotopes were in her fetlocks, more in the front than in the rear. Everything checks out fine but she is in pain when traveling downhill and after any but the lightest use. Any ideas?