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What is Patellar Luxation

What is Patellar Luxation?


Our two-year old mixed poodle has had a problem with his right hind leg since he was a young dog. The problem is that occasionally his right rear leg seems to “freeze up”. When this occurs, he will either stop walking or walk on three legs with the right hind leg held up in the air. Sometimes the leg will go back down and other times it pops back after we massage it. I thought it would get better as he grew older but it has not. Any idea of what the problem might be and what we should do about it? It doesn't seem to slow him down or even cause any pain or discomfort.


Based on your description, it is possible that your dog may have a condition called "patellar luxation". A "luxated patella" occurs when a kneecap dislocates i.e. slips out of place. It is a common problem among small breeds of dog, such as Pomeranians, poodles, and Yorkshire terriers. In fact, one study showed that dogs that weigh less than 9 kg are twelve times more likely to be affected than larger dogs. In many dogs, both hind legs may be affected.

A luxated patella is an inherited condition that is present at birth, even though there may not be any evidence of a problem at that time.  However, since all of the anatomical abnormalities that cause patellar luxations are usually in place in the knee joint, it is only a matter of time before clinical signs such as the ones you described begin to appear.

In a normal stifle, the patella (knee cap) rests in a groove on the femur. The purpose of the patella is to permit the large tendon of the thigh muscle (called "quadriceps") to ride over the front of the femur during movement. Luxation or dislocation of the patella occurs when the femur and tibia bones are out of alignment and the patella slips out of its groove. When this happens, the dog usually does not bear weight on the leg but holds it up instead.  Eventually, the patella slips back into its groove and the leg goes back to its normal position.

The symptoms of patellar luxation can appear as early as weaning or may go undetected until later on in life. Signs include intermittent hind leg lameness (sometimes shifting from one leg to the other) or holding the leg up for short periods of time, as is the case with your dog. The condition is usually not painful. However, because of the unusual stresses and strains placed on the knee joint by the dislocations, arthritic degenerative changes and future ligament ruptures may occur.     

In mild cases, medical or surgical treatment is usually not required. However, more severe cases may require surgical correction of the deformities. There are several techniques currently available and the prognosis for recovery is good if the joints are not too badly damaged. I would suggest you have your dog's knees evaluated by your veterinarian to determine whether medical and/or surgical intervention is required.