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.

Is luxation serious?
There are four degrees (grades) of luxation:

I. The knee only slips out when the vet manipulates it.
II. The knee luxates occasionally when your Yorkie is walking or running. She may not seem to mind much, or she may shriek, but it usually slides back by itself as she continues moving. Or you can slip it back manually (ask the vet to show you how).
III. The knee luxates frequently and causes chronic lameness. Even when you put it back manually, it doesn't seem to last long.
IV. The knee luxates, stays that way, and you can't put it back into its socket. This grade is very rare.

•The first treatment should be to crated for a week or two and supervise the activity - no jumping.
•Non-steroidal anti-inflammatories (like Rimadyl). These will hide the symptoms, but do absolutely nothing to strengthen or correct the knee.
•Steroidal anti-inflammatories. These are extremely damaging to the immune system, have awful side effects (short and long term), and should never be used.
•Surgery. Surgery is seldom the answer and should only be done by an orthopedic surgeon. Call the American College of Veterinary Surgeons at (301) 718-6504 and ask for a referral to an orthopedic specialist or college of veterinary medicine in your state. If surgery is your choice, that dog will have problems down the road with arthritis from the surgery. In the opinion of most vets, surgery is over-kill for Grade I or II luxating patella. I would only go with surgery on a Grade IV luxation, or on a Grade I II that did not respond to natural treatment. Surgery costs about five hundred dollars per leg, it is uncomfortable for your Yorkie, and there is a 50% chance that some degree of luxation will return.

Natural ways to treat your Yorkie:

•Feed fresh foods.
•Keep your Yorkie lean. Fat dogs have to carry more weight on their weak leg joint.
•Moderate exercise, walking up slight inclines (gentle hills), will strengthen the muscle groups around the patella.
•Vitamin C is one of the building blocks of strong ligaments and connective tissue.
Glyco-flex and Glucosamine are nutritional products packed with minerals, amino acids, enzymes, and lubricating agents. They build cartilege and cushioning fluid in injured joints, and help heal damaged connective tissue.

What causes luxating patella?

Occasionally it's caused by an injury, but in the absence of such proof, the weak tendons and/or shallow kneecap groove of luxating patella is considered hereditary. Never breed a Yorkie with any degree of luxation (even a "wiggly" knee), whether it has been repaired or not. Fixing the knee doesn't fix the genes that caused the problem.

OFA Certification
The Orthopedic Foundation of America will issue registration numbers to dogs whose patellas have been x-rayed by a vet, forwarded to the OFA, and found to be normal. This condition is so common in Yorkies that we believe it is essential that all breeders start doing these x-rays before breeding. Then you will be able to INSIST on seeing the OFA certificate for each parent before buying a Yorkie puppy. It will be one more way to pick out the responsible breeders from the rest of the pack.

Sources
•Chihuahua Kingdom Retrieved February 1998 from the WWW http://3lbdogs.com/wellness/
•Shumsky, Terri (1993) How to buy your Toy Dog, and Raise it Inexpensively California Creations by Terri.