If you are exercising her too much for her to handle, that could be the problem. try equine massage, if it is her muscles, then that will help her loosen up. If it is her bones, it might be the early stages of arthritis. The best thing to do would be to talk to your vet and try the IceVibe hock and front boots to see if that made any difference. i once had a horse in my barn with arthritis in his joints and they helped when being use regularly.