Patellar luxation occurs when the dog’s kneecap (patella) is dislocated from its normalanatomic position in the groove of the thigh bone (femur). When the kneecap is dislocated from the groove of the thigh bone, it can only be returned to its normal position once the quadriceps muscles in the hind legs of the animal relax and lengthen. It is for this reason that most dogs with the condition will hold up their hind legs for a few minutes.
A dislocated kneecap is one of the most prevalent knee joint abnormalities in dogs. The condition is most common in toy and miniature dog breeds such as the Yorkie, Pomeranian, Pekingese, Chihuahua, and Boston Terrier.