How Does a Veterinarian Diagnose and Grade Patellar Luxation?

Patellar luxation in dogs varies in severity, just as many other conditions do. Veterinarians use a scale from I to IV to grade patellar luxation, with IV being the most severe. Dr. Mark Hein at Wisconsin Veterinary Orthopedics in Holmen will perform several types of examinations on your dog if it is showing signs of knee pain.

To begin this examination, our veterinarian will lay the dog on its side and extend the affected leg. He will twist the leg outward with one hand while manually applying pressure to the patella with his fingers. This allows him to check to see how much the patella moves. He will then repeat the process, twisting the leg inward this time. Our vet surgeon will the grade the dog’s condition according to the following scale:

Grades of Patellar Luxation

Grade I

A Grade I luxation means that the patella moves with manual pressure, but will return to normal position in the groove at the base of the femur when pressure is removed. Dogs with Grade 1 luxation often have no symptoms, although they sometimes limp for a few steps and then return to normal. This is called “skipping.” Grade 1 luxation does not require surgery.

Grade II

With Grade II, the knee cap moves on its own outside of its groove. Owners will notice more frequent skipping in their dog’s gait. The patella can be moved back into place with manual pressure. Orthopedic surgery for dogs is recommended only when limping or skipping is severe in patients with Grade II.

Grade III

Some Grade II patella luxation can evolve into Grade III as bone and cartilage erode. In Grade III, the patella is permanently luxated, meaning it’s always out of its groove. The patella can be manually moved back into place, however. Owners will notice much more limping or lameness in their dogs. Some owners may notice a “crouched” gait, where one leg is partly flexed or rotated in an abnormal position.

Grade IV

With Grade IV luxation, the patella is permanently luxated and cannot be manually moved back into position. Owners will see the same symptoms as described for Grade III. Orthopedic surgery for dogs is strongly recommended in cases of Grade III and Grade IV.

Call Our Vet Surgeon if Your Dog Shows Any Signs of Knee Pain

Like any other medical condition, the prognosis for patella luxation is better the earlier that treatment begins. If you see your dog skipping or limping occasionally or see any other signs of knee pain, call Wisconsin Veterinary Orthopedics in Holmen today to schedule an appointment with our experienced vet surgeon.