The patella is the small bone also known as the kneecap, and patella luxation simply means a dislocating kneecap. Patella luxation is a relatively common condition affecting dogs and occasionally cats. When a normal healthy knee joint bends the patella slides up and down the grove in the thigh bone. The patella is located in the quadriceps tendon, which attaches the quadriceps muscle of the thigh to the tibia, or shin. Any breed or size of dog can be affected by patella luxation; however, it is a condition most often seen in small and toy breed dogs.

What are the symptoms of patella luxation?

When the patella luxates, it slips out of the grove of the thigh bone and stops the knee bending. This dislocation of the kneecap can cause pain, wear and tear of the patella and surrounding bone of the grove as it slips past, over time this can lead to arthritis. Most commonly the patella luxates medially, meaning it slips towards the inside of the leg.

The most commonly seen symptom is a skipping lameness of the hindlimb, the dog is seen to ‘skip’ or hold up the affected leg for a few steps before recovering. If both legs are affected a “bunny hop” or stilted gait may be seen. Most often the signs are intermittent and in mild cases symptoms may only be very rarely seen. In more serious cases there can be ongoing lameness, or a stiff gait. Symptoms often start in puppyhood or in young adult dogs, but signs can occur at any age. Patella luxation can affect just one hindlimb or both.

Dogs with a more “bow legged” appearance are more at risk of patella luxation due to the conformation of their hindlimbs. The cause of patella luxation is down to genetic predisposition. Some dogs have been selectively bred in such a way that their conformation predisposes to this abnormality developing as they grow. 

What types of patella luxation impact dogs?

Patella luxation is graded according to its severity and how mobile the kneecap is. 

Grade 1 patella luxation: the patella can be dislocated with manual pressure on examination but otherwise remains in place. In the majority of cases it does not cause a serious problem.

Grade 2 patella luxation: the patella luxates occasionally as the dog moves around, and a skipping lameness might be seen. Signs may be mild to moderate, according to how often the dislocation happens.

Grade 3 patella luxation: The kneecap is always dislocated but can be moved back into the groove when examined by the vet. 

Grade 4 patella luxation: the kneecap is always dislocated but cannot be moved back into the groove when examined by the vet.

Diagnosis of patella luxation

Patella luxation may be picked up during a routine health check with the vet or following an episode of lameness. When the vet examines the leg, they may be able to feel the kneecap dislocating when it is manipulated. Often x-rays are recommended to investigate further and decide on the appropriate course of treatment. 

If you suspect your dog may be experiencing patella luxation or is showing signs of lameness arrange a check-up with your vet.

Treatment options for patella luxation

For those dogs experiencing only very mild symptoms and those with grade 1 patella luxation treatment may not be needed. In dogs with mild or intermittent symptoms physiotherapy and modification of their exercise regime may be enough to improve the situation.

Dogs with a grade 2 patella luxation also rarely require surgical intervention. Often physiotherapy and exercise modification are enough to improve symptoms. However, in the case of severe or ongoing pain surgery is occasionally recommended.

Dogs with grade 3 or 4 patella luxation often require surgery to correct the abnormality and avoid ongoing issues with pain and lameness.

The type of surgery which is appropriate for a dog with patella luxation will depend on the dog’s individual needs and conformation. The options and decision on the surgical treatment can be discussed with your vet, as the management of each case will vary. Surgical aims when treating patella luxation can include:

  • Deepening the trochlear groove which the patella travels in.
  • Moving the tibial crest (the ridge of bone where the quadriceps attach to the shinbone) laterally (outwards) to correct the alignment of the patella mechanism. 
  • Correction of femoral bowing (straightening the leg) in severe cases.
  • Soft tissue reconstruction to loosen or tighten the surrounding soft tissue structures as needed.

Patella luxation is a common and treatable condition. If you suspect your dog may be showing signs of patella luxation arrange a check up with your veterinary practice. 

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