Luxating Patella in Dogs

Source: PDSA

A luxating patella is a knee cap which dislocates, or 'luxates' - it pops sideways, out of place from the groove in the bottom of the femur bone that it normally sits in. It can occur medially (moves toward the midline of the body or towards the other leg - which is the most common) or laterally (moves towards the outside/away from the other leg).

Grades of Luxating Patella

Luxating patellas are graded depending on severity:

Grade 1: The patella can be luxated, but spontaneous luxation of the patella during normal joint motion rarely occurs. Generally dogs with a grade 1 luxation show no lameness, and the diagnosis is made as an incidental finding on physical exam.
Grade 2: The patella luxates occasionally with flexion and extension of the joint, but reduces spontaneously. Dogs with grade 2 luxations may sometimes 'skip' when walking or running, caused by the leg being unable to extend when the patella is luxated.
Grade 3: The patella luxates consistently, however the person examining can reduce it back into the groove. It is classed more as a mechanical lameness as the joint is often abnormally positioned and the hind legs may have a bow-legged and/or pigeon-toed appearance if there is a medial luxation. If it's a lateral patellar luxation - then the legs may have a knock knee'd appearance. Dogs with a grade 3 luxating patella may crouch in their back legs while walking.
Grade 4: The patella is consistently luxated and is unable to be reduced back into place. This causes the dog to walk with a crouched appearance as his knees are bent consistently. This limb is readily seen as abnormal, as seen in Grade 3.

While the luxation itself is not painful, the sliding of the patella in and out of the groove damages the lubricating cartilage and flattens the groove which can lead to osteoarthritis, or arthritis, reduced mobility and limb changes.

What Causes Luxating Patellas in dogs?

Luxating patellas are usually a developmental disease with the onset occurring during growth.

Which Breeds are Prone to Luxating Patellas?

Luxating patellas can occur in both sexes in any breed of dog (and cat), but mostly occurs in toy and miniature breeds. Large breeds, such as Newfoundlands, have a higher percentage of lateral patella luxations compared to small breed dogs.

Patellar luxation has been shown to be heritable in toy spaniels and toy and miniature poodles.

Signs of Luxating Patellas

The signs and symptoms of luxating patellas will vary depending on the grade of luxation.

In grade 1 luxations, there are generally no noticeable symptoms, and the diagnosis is made as an incidental finding on physical examination.

Symptoms associated with a grade 2 luxation are usually occasional skipping in the affected back leg. The dog will flex the limb and hold it up for a few steps and then walk normally again. Occasionally, the tissues around the knee joint will become stretched and lead to lameness where the dog will not bear weight on the affected leg.

Over time, a grade 2 luxation can progess to a grade 3 luxation through the flattening of the groove, and can also lead to arthritis in the joint.

With grade 3 and 4 luxations, the symptoms tend to be more constant. These include:

More severe luxations will lead to arthritis in the knee joint. The common symptoms of arthritis are:

Diagnosis of Luxating Patellas

The diagnosis of patellar luxation is usually made on the basis of the symptoms and physical examination. Xrays are usually performed if surgery is planned as they can pick up other associated disorders such as cranial cruciate ligament tears and concurrent osteoarthritis.

Treatment of Luxating Patellas

The treatment for patellar luxation will once again depend on the grade of the luxation.

Grade 1 luxations are managed conservatively with medical management. Grade 2 luxations may be treated medically, or surgery may be warranted based on the frequency of luxation and/or the level of lameness, or to prevent the condition progressing to higher grades. Grade 3 and 4 lucations should be treated surgically.

Medical Management

Medical management for patellar luxation is aimed at delaying the onset, or severity, of arthritis in the joint.

Joint Supplements

There are a number of natural extracts and herbal products with proven anti-inflammatory properties. Some are antioxidants, which slow the actual progression of arthritis, while others intercept the inflammatory cascade to limit pain and inflammation.

Green Lipped Mussel (Perna canaliculus)

Green Lipped Mussel for dogs contains key omega-3 polyunsaturated fatty acids, glycosaminoglycans (a source of chondroitin), vitamins and minerals which have been shown to have beneficial anti-inflammatory effects in dogs with arthritis. Similar to other joint supplements, it may take several weeks to notice visible effects, however it has been shown to play a role in reducing inflammation and pain in the joints.

Glucosamine and Chondroitin

Glucosamine for dogs and Chondroitin are the building blocks of normal healthy cartilage. Despite a lack of strong evidence in the veterinary literature, some veterinarians and owners have found supplementation to be helpful. With minimal side effects compared to some of the common pain relief medications, they are a good option for mild cases and to use alongside other therapies.

Omega Fatty Acids

Omega 3 fatty acids DHA and EPA have been demonstrated to have anti inflammatory properties, and as far as supplements for arthritis go, they are backed by the most convincing evidence. Omega 3's can be obtained from lots of difference sources including fish oil, green lipped mussel powder, flaxseeds and nuts. Marine sources of omega fatty acids (such as fish, fish oil and green lipped mussel) are the most effective for dogs.