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Luxating Patella in Dogs
What is a luxating patella?
A patella is a kneecap, and “luxating” means out of place or dislocated. So, a luxating patella is a kneecap that moves out of its normal location. The knee joint connects the femur (thighbone) and the tibia (shinbone). The patella is normally located in a groove (the trochlear groove) at the end of the femur, but with a luxating patella, it moves out of this position.
What causes patellar luxation?
The kneecap sits underneath a ligament called the patellar ligament. This ligament attaches the large thigh muscles to a point on the center front of the shinbone. When the thigh muscles contract, the force is transmitted through the patellar ligament, pulling on the shinbone and causing the knee (and leg) to extend or straighten. The patella slides up and down in its groove and helps keep the patellar ligament in place during this movement.
In some dogs, especially those that are bowlegged, the patella may luxate because the point where the patellar ligament attaches is not in the center of the shinbone. In these cases, the ligament is almost always located too far toward the middle of the body or the inside of the leg. As the thigh muscles contract, the force applied to the patella pulls it to the inside of the knee (medial luxation). After several months or years of this abnormal movement, the inner side of the groove in the femur may wear down. Once this happens, the patella is then free to dislocate or slide toward the inside of the knee.
Many toy and small-breed dogs, including Maltese, chihuahua, French poodle, and bichon frise, have a genetic predisposition for a medial luxating patella. In some dogs, a condition can occur where the kneecap slips to the “outside” of the leg, called lateral patellar luxation. Dogs with this condition are often medium- or large-sized dogs, with a genetic predisposition noted most in Great Danes, Irish wolfhounds and St. Bernards. These dogs tend to have more mobility issues than those with medial patellar luxation.
How severe is this condition?
There are four grades of patellar luxation, and a higher grade means the condition is more severe.
In affected dogs, one or both kneecaps may luxate, sometimes to a different degree. Approximately 50% of affected dogs have both knees involved.
Pet owners may notice a skip in their dog’s step or see their dog run on three legs; then, suddenly, the dog will be back on all four legs as if nothing happened.
With medial patellar luxation, the dog will usually hold up the lower part of the leg as long as the kneecap is out of place. When the kneecap returns to its normal position, the dog can resume normal walking. Many dogs with medial luxation learn how to kick the leg to the side, which causes the knee to hyperextend and “snaps” the patella back into place. Over time, the soft tissues around the joint become damaged or stretched, and it becomes easier for the kneecap to pop out of place.
Dogs with lateral patellar luxation may have more difficulty walking. Small dogs may develop this condition suddenly and start limping or, if it develops in both knees at the same time, they may lose the ability to stand properly. In large dogs, lateral patellar luxation is often a developmental condition. As the affected puppy grows, they develop a “knock-kneed” stance, with the knees turning inwards and the paws pivoting as they walk.
Your veterinarian will diagnose a luxating patella by feeling the abnormal movement or position of the kneecap during palpation of the leg. In some cases, the luxating patella will be detected during a routine physical examination. In other cases, a history of intermittent lameness may suggest this problem and your veterinarian will examine the leg to confirm patellar luxation. Radiographs (X-rays) are usually performed to determine the extent of the problem and to detect whether there are any other changes or abnormalities in the joint, particularly if the luxation is caused by trauma.
A luxating patella can cause long-term problems for your dog, but the severity depends on the grade of luxation and whether both legs are affected to the same degree. The higher the grade, the more likely your dog will develop long-term problems. Some dogs, especially with Grade I patellar luxation, can tolerate this condition for many years, even their entire lives; however, as the dog ages, arthritis develops and results in decreased mobility and joint pain. Once arthritis develops, it cannot be reversed. In addition, patellar luxation predisposes the knee to other injuries, especially torn cruciate ligaments.
A luxating patella can be surgically corrected, especially if the patella luxates frequently. With mild Grade I luxation, surgery may not be necessary. For most dogs with patellar luxation, surgery may be recommended sooner rather than later to minimize the likelihood that arthritis or a cruciate ligament tear will develop. The higher the grade of luxation, the sooner the surgery should be performed.
Surgical repair may involve several techniques depending on your dog’s knee structure, including:
After surgery, recovery is usually rapid, especially with appropriate pain management.
If your veterinarian performs surgery before arthritis or another knee injury occurs, the prognosis is excellent. Your dog should regain full use of the leg. However, if arthritis has already developed in the knee joint, your dog may experience intermittent pain in the leg and it may progress. Prescription anti-inflammatories, antibody therapy (Librela®), joint supplements, and therapeutic mobility diets may slow the progression of arthritis and help control any discomfort. Weight reduction is also recommended for overweight dogs. Post-operative physiotherapy may be recommended. Your veterinarian can help you determine the best post-operative plan for your dog.
© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Jun 27, 2025.
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