Patella Luxation - What is it?

Patella luxation is probably the most common defect in the Chihuahua breed. OFA (Orthopedic Foundation for Animals) lists the Chihuahua as having a 10% affected rate, however, this may very well be quite underestimated as people who have a dog with Patella luxation might not even submit the paperwork to OFA. 

Although patella luxation is fairly easy to diagnose, some owners are unaware that they do have a problem (they think that if their dogs are walking around fine, they don't have any problems), or are not checking their dogs properly. A skilled veterinarian can easily determine if a Chihuahua has any looseness in the patella joint, or if the patella itself  luxates. 

Owners can also become skilled, if properly taught, to determine if a dog has patella luxation or not. Patella luxation can either have genetic causes, or environmental causes (i.e. injury). If patella luxation shows up at an early age (under 7 months or so), it is probably due to genetic causes; however, injury might also cause patella luxation to show up in the first seven months. Sources of injury could include being overweight, too much jumping (i.e. jumping off furniture), or too much stress on the patella and surrounding ligaments (ie. a dog dancing on its rear legs). 

These causes are especially dangerous when a Chihuahua is in the developmental stages...from a young puppy to 1 or 2 years of age. Chihuahuas might also damage their kneecap by hitting it, and even an unskilled veterinarian might cause permanent looseness if he is forcibly trying to see if the patella is loose. As a Chihuahua ages, slight looseness might be seen, especially in dogs that are very overweight and have continued pressure on the ligaments/patella.

Visual signs of grade 2 (and higher) patella luxation includes skipping, holding the rear leg up for a short time as the dog walks/runs or rear-leg weakness. Grade 1 patella luxation does not usually have any visual signs (which is why some owners might be unaware they have a problem) except the patella can manually be pushed out of place quite easily by hand. Patella luxation can cause permanent lameness later on, as well as arthritis, especially in the more serious cases (grade 2 and higher).

If your dog does have this painful problem, your veterinarian might be able to give you some options to help alleviate the symptoms, depending on the seriousness of the problem. This might include keeping the dog lean (ie. not letting the dog get fat), the use of joint supplements such as glucosamine/choroditin, pain killers, or surgery.