Kneecap Dislocation in Dogs

A patellar luxation occurs when your dog’s kneecap is dislocated or slides out of its normal position. Dislocated kneecaps are usually due to a congenital defect, but can also be the result of trauma. This condition is the most common in young, small, or toy breeds, including:

• Yorkshire Terrier
• Pomeranian
• Chihuahua
• Boston Terrier
• Pekingese
• Papillons
• Jack Russell Terriers
• Maltese
• Miniature Poodles

Certain large breed dogs are also predisposed to the patellar luxation, especially if they suffer from hip dysplasia. Treatment alternates according to the severity, or grade, of the luxation, but the prognosis is typically good.

Symptoms of patellar luxation vary according to the severity of the condition and include:

• Limping or lameness
• Reluctance to place weight on the limb
• Discomfort

The clinical signs are often intermittent and sudden. Your dog may exhibit an irregular gait for a few steps, usually with one limb raised from the ground, before resuming a normal walk.

Types

There are two types of patellar luxation in dogs: medial and lateral:

• Medial luxation, which is the more common form, occurs when the dog’s joint slips towards the opposite leg. This prevents the dog from extending its knee normally though often times the kneecap will slide back into position by itself after a few steps.
• With lateral luxation, the kneecap slips to the outside of the leg, away from the body. This form of patellar luxation tends to impact the dog more severely and is more common in large breed dogs, where hip problems may lead to misaligned bones in the legs.

Patellar luxation transpires when the kneecap slips out of the groove in which it normally sits. This groove is shallower in many small or toy breed dogs, such as Chihuahuas, Maltese, and Yorkshire terriers, resulting in a genetic predisposition for the condition. A kneecap can also become dislocated as a result of trauma, and there has been a rise in occurrences in larger dogs, including Akitas, Boxers, and Golden Retrievers.

Most cases of patellar luxation in small dogs are diagnosed early on during a veterinary examintion. If the kneecap is dislocated at the time of your office visit, the veterinarian can easily diagnose the condition with a physical examination of the affected limb. The diagnosis can be confirmed via x-rays, which also help determine the extent of the condition and reveal the shape of the bones.

Patellar luxation is often graded based on severity, with levels ranging from 1 to 4. With grade 1 luxation, the kneecap sits normally but can luxate under slight pressure because of the shallowness of the groove. Grades 2 and 3 are more severe though the joint can typically still be replaced manually. A luxation is classified as grade 4 if the joint sits outside of the groove at all times and will not stay seated if replaced. Treatment depends on the severity of the luxation, so it is important that the veterinarian receives enough information to grade your dog’s condition appropriately.

Treatment varies according to the grade that the veterinarian diagnoses.

Supportive Treatment

If your dog is diagnosed with grade 1 luxation, surgery is not typically recommended. Instead, you can help prevent the kneecap from sliding out of place with regular exercise and supportive nutrients. It's critically important to reduce stress exerted on the knee by ensuring that your dog is at a proper weight for its size, and strengthen the muscles surrounding it through daily exercise. Nutritional supplements, such as glucosamine and chondroitin, provide support to the joint and its surrounding tissues.

Surgical Treatment

Surgery is usually recommended for luxated patellar graded 2 or above and is necessary for grade 4. There are different types of operations available though the goal is always to replace the kneecap to it's suggested, normal position and prevent future slipping. This can be accomplished by deepening the groove in which the patella sits or by tightening the joint capsule to prevent slippage. In more severe cases, the leg bones may need to be rotated back into the correct position as part of treatment.

Most dogs recover fully once the kneecap has been replaced though you will need to restrict your dog’s activity until the surgical site has healed. Provide a quiet place where your dog can rest, and make sure that it doesn’t bite or chew at the incisions. If the veterinarian prescribed antibiotics as a preventative measure against infection, be sure to administer the full course.

Your dog will most likely begin to use the affected leg again in one to two weeks following surgery. If your dog is still reluctant to place weight on the leg several weeks after treatment, contact the veterinarian, and ask how you can retrain your dog to use that leg. Many dogs benefit from physical therapy after surgery.   Follow-up exams may be necessary, depending on the treatment. In all cases, continue to monitor your dog for signs of a displaced joint, as the condition may recur or arise in a different knee.