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Medial Patellar Luxation (MPL)

What is a Medial Patellar Luxation?

Medial patellar luxation is a condition in which the kneecap (patella) pops out of its groove. It can pop to the inside of the knee or the outside of the knee making the knee quite unstable. This condition is often diagnosed in small breed dogs, frequently effecting both rear legs and can be either traumatic or congenital. Congenital MPL is far more common and is most often the cause of MPL in small dog breeds and in cats. In large breeds, MPL can be due to a congenital problem but can also occur secondary to trauma. MPL occurs most commonly in breeds such as Yorkshire Terriers, Maltese, Papillion, Miniature Poodles, but also can be seen in Labrador Retrievers, Great Pyrenees, and other large breeds.

The condition is usually first detected in 6-12 month old puppies and the condition can worsen over time from a mild and only occasionally popping patella to a chronically luxated patella that cannot be put back into the femoral groove anymore. This is called a Grade 4 medial patellar luxation.