March 24, 2026, 4:58 am | Read time: 4 minutes
If a dog suddenly runs on three legs and then returns to normal, it’s often dismissed as harmless. However, this typical “hopping” can indicate a patellar luxation in the dog—a change in the knee joint. What signs owners should be aware of, and how the condition develops, is covered below.
What Happens in the Knee Joint
The dog’s knee joint is a complex connection of several bones: the femur, tibia, and patella. The patella sits in a tendon and normally glides in a small groove on the femur. It ensures that the muscle’s force is effectively transferred to the leg.1, 2
In a patellar luxation, the patella leaves this designated path. It slips inward or outward from the groove, disrupting the joint’s movement. The leg can no longer extend properly, and the joint is unevenly stressed.3
The problem: If the patella keeps popping out, it rubs against the joint. Over time, this can damage the cartilage. The result can be osteoarthritis—a wear and tear of the joint that further limits mobility.
Why It Happens
A patellar luxation in dogs usually doesn’t result from a single cause but from multiple factors. Genetic predisposition often plays a significant role. Small dog breeds such as Chihuahuas, Yorkshire terriers, or poodles are particularly affected.4
They often have a misalignment of the hind legs, such as bow-leggedness. A shallow groove in the femur or an unfavorable alignment of bones and joints also promotes the patella slipping out.
External factors can also be considered. Injuries from falls or accidents can trigger a patellar luxation. Additionally, significant stress on the hind legs, such as from obesity, is described as a potential risk factor. In some cases, age-related wear and tear also plays a role.
How to Recognize a Patellar Luxation in Dogs
The most noticeable sign is easily recognized by many owners but often misinterpreted: the so-called “hopping” or “limping” gait. The dog suddenly lifts a hind leg and walks on three legs for a few steps. Then it sets the leg down normally again and initially shows no more abnormalities.
Over time, the symptoms can become more pronounced. Lameness occurs more frequently or lasts longer. If both hind legs are affected, the gait often appears stiff, with small, uncertain steps.
It’s important to know: In mild cases, dogs show no visible symptoms for a long time. In other cases—especially after injuries—pain can occur, leading the dog to move less or react sensitively.
How the Veterinarian Diagnoses It
If the gait changes noticeably, it should definitely be checked by a veterinarian. They can specifically examine and palpate the knee joint.
The gait is also assessed. Based on this, the patellar luxation is classified into four severity levels. These indicate how easily the patella slips out of position and whether it returns on its own.
X-rays are often used additionally. They help identify changes in the joint and rule out other causes. In more complex cases, further imaging techniques such as CT or MRI may be useful.
What Treatment Is Possible
The treatment depends heavily on the severity and symptoms. In mild forms without symptoms, direct treatment is often not necessary. If the dog only occasionally shows abnormalities, conservative measures are prioritized. This mainly includes maintaining a healthy body weight to relieve the joints.
Physical therapy can help strengthen the muscles and stabilize the knee. Additionally, it may be beneficial to limit strenuous movements. Pain-relieving medications are used if needed.
It’s different in more severe cases: If lameness persists or worsens, surgery may be required. The goal is to permanently stabilize the patella. Various procedures are available, such as deepening the groove or adjusting tendons and bones. After surgery, a period of restricted movement follows. Physical therapy then supports recovery.
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What the Prognosis Is
The prognosis depends on how severe the patellar luxation is and whether there are already secondary damages. Dogs without significant symptoms can often live well with the condition for many years. If the condition worsens, surgery can significantly improve joint stability—especially if done early.
However, a risk remains: Many affected dogs develop osteoarthritis over time, which requires ongoing management. In large dogs, the prognosis is sometimes less favorable. The reason: Additional problems in the musculoskeletal system occur more frequently.
What Owners Can Do Preventively
Complete prevention is not possible, as genetic factors play a significant role. However, owners can do several things to influence the risk. Maintaining a stable, healthy body weight significantly relieves the joints. Regular exercise strengthens the muscles and supports knee stability. At the same time, heavy loads—such as frequent jumping—should be avoided as much as possible.
Attention in everyday life is crucial: Changes in gait should be taken seriously and checked early. Regular veterinary check-ups help monitor the condition.