Luxating is a fancy word for dislocating. Patella is your dog's "knee", the joint on the front of her hind leg. So a luxating patella is a dislocating knee or trick knee, a knee that keeps slipping out of its socket. This can happen in yorkies with weak ligaments, tendons, and/or muscles. It can also happen in Yorkies whose kneecap groove is too narrow or shallow. The knee usually slips inwardly, toward her body, and locks so that your Yorkie can't bend her leg.
Suspect luxating patella if your Yorkie sometimes lifts one hind leg while she is running, or if she often moves both rear legs at the same time, like a hopping bunny. Sometimes the knee slips only for a few moments, then slides back into place. Sometimes the knee slips out and stays out, and your Yorkie will hold her leg off the ground and limp, perhaps tucking her thigh into her body. Luxation may occur in one knee, or in both. It is seen in many other toy breeds, and in both sexes, though it seems to be more common in females. No matter how firm the knees seem as puppies, toy dogs are liable to injure their knees.
Vitamin or food suppliments?