Overview 

Patellar luxation is a common orthopedic condition describing kneecap dislocation.  

This condition is more common in small breed dogs, such as Toy Poodles, Yorkshire Terriers, Chihuahuas and Pomeranians, but it can also occur in large breeds.  

The most commonly seen sign is a “skipping” gait, which looks like a sudden three-legged hindlimb lameness that quickly resolves after a few steps. While some dogs have mild luxation that only needs conservative management, more severe cases will benefit from surgical correction.  

Cause 

The exact cause of patellar luxation is based on many factors, but genetics play a significant role. Patellar luxation can also occur following trauma.  

The patella is a small bone in the knee joint, situated within a tendon. The patellar tendon sits in a groove at the end of the thighbone (femur) and attaches just below the knee onto the shin bone (tibia). Patellar luxation occurs when the kneecap slides or pops out of place from the femoral groove when the knee flexes, causing the dislocation.  

Dogs with patellar luxation tend to have a more shallow femoral groove or a general malalignment of the limb involving the femur, tibia or hip. Luxations can occur on one or both knees, and the dislocation can be either medial or lateral (moving towards the inner or outer aspect of the knee, respectively).  

Medial Patellar Luxation (MPL) is more common, and signs often develop early in a dog’s life — most commonly affecting small breed dogs. Lateral luxation occurs less frequently, but it is more common in medium or large-breed dogs, often in tandem with hip dysplasia.  

As patellar luxation progresses, the patella dislocates more easily and frequently — persistently rubbing on the knee joint cartilage and leading to arthritis. The strain from the patella dislocating can also predispose dogs to other orthopedic knee conditions, such as cranial cruciate ligament rupture.  

Clinical signs 

The clinical signs for patellar luxation vary depending on the extent of the disease, and mild cases often remain asymptomatic.  

The most common sign is an intermittent “skipping” lameness when one hindlimb is suddenly lifted for a few “skips,” and then the dog resumes walking normally after kicking or shaking the limb.  

Patellar luxation may progress over time, causing more frequent bouts of lameness.  

Diagnosis 

Your veterinarian will perform a physical exam to diagnose patellar luxation and assign a grade of 1-4 to help guide treatment recommendations based on the severity of luxation.  

X-rays may be recommended to further evaluate the affected limb for contributing orthopedic abnormalities. Advanced imaging, such as a CT or MRI, may be recommended in some cases.  

Treatment 

Treatment of patellar luxation depends on the severity of the condition and a dog’s individual clinical signs.  

Most mild cases without clinical signs do not require any treatment. Conservative medical management for dogs with intermittent or infrequent lameness, or for those who have developed arthritis secondary to patellar luxation, treatment may include the following:  

• Maintaining an ideal weight  

• Joint supplements 

• Pain medications (e.g., nonsteroidal anti-inflammatories or NSAIDs) 

• Exercise restriction   

• Physical rehabilitation  

Your veterinarian may recommend surgery if your dog has more advanced patellar luxation or persistent lameness. If you choose to move forward with an operation, there are a few different surgical approaches, and your veterinarian will help determine which is best for your dog. 

Outcome 

Dogs without significant clinical signs of patella luxation generally have a good prognosis, and their condition can be managed comfortably for many years.  

For dogs with more severe luxation and significant clinical signs, surgical correction often leads to good outcomes with restored kneecap stability — especially if performed before the onset of arthritis. With or without surgery, many dogs with more severe luxation or persistent clinical signs may develop arthritis that requires medical management.  

Large breed dogs with patella luxation may have a less favorable prognosis, since they often have additional orthopedic conditions, such as hip dysplasia or abnormally shaped femurs, which contribute to their patella luxation.