Knee injuries are common in both big and small dogs. While large dogs may tend towards injuries to the ligaments in the knee, the most common knee injury I see in small and toy breed dogs besides ruptured cruciate ligaments is called patellar luxation.

What is a luxating patella?

In this condition, the patella (knee cap) slides in and out of place, causing lameness.

According to the American College of Veterinary Services, patellar luxation is one of the most common orthopedic conditions in dogs, diagnosed in 7% of puppies.

Signs and symptoms in dogs

Much like ourselves, our dogs' knees are made up of the meeting of the large bone of the upper leg (the femur) with the bone of the lower leg (the tibia). The patella, or knee cap, sits nicely in a groove in the middle of the lower end of the femur, where it can slide easily up and down as the knee bends.

The most common sign of a luxating patella is intermittent lameness. Affected dogs will seem to have a temporary hitch in their gait that resolves quickly with no treatment.

Often, I will find luxating patellas on a routine annual physical exam and mention it to the owners who had no idea! The intermittent lameness results from the knee cap temporarily slipping out of the groove in the femur. The knee cap will shift to one side (usually to the inside of the knee in small dogs) and cause discomfort before slipping right back into its normal position in the middle of the knee.

Luxating patellas are graded based on their severity as follows:

Grade 1: The patella slides out of joint when manually manipulated, but will slide right back into place on its own.

Grade 2: The patella slides out of joint when manually manipulated and stays there.

Grade 3: The patella remains out of joint, but can be put back into place manually.

Grade 4: The patella remains out of joint and cannot be manually replaced.

Patella luxation grades in dogs

In all grades of luxating patella, the knee joint becomes more prone to degenerative joint disease over time. Treatment of this condition depends on the grade of disease.

Dogs with Grade 1 disease generally do not require surgery, though from time to time, they may need anti-inflammatories to ease discomfort.

Dogs with Grade 2 disease may benefit from surgery - generally this decision is made on a case by case basis.

Dogs with Grade 3 or 4 patellar luxations need surgery to repair their conformation and prevent further joint damage and pain.

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Treating luxating patellas in pets

If you have noticed a hitch in your dog’s get-a-long, make sure your veterinarian checks her knees. If patellar luxation is found in one or both knees, talk to your veterinarian about your treatment options.

According to Petplan 2018 claims data, patella luxation cost pets $1,730 on average, but a pet insurance policy can help cover these costs. 

Often, symptomatic treatment of discomfort is all that is needed, but if surgery is required, you may be referred to an orthopedic specialist. Don’t despair if your precious pet needs surgery; within six to eight weeks, your pup’s knees will be as good as new.

Aug 8, 2011
Pet Health

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