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Luxating patellas in dogs

Team Walmart Pets

June 1, 2021

4

min read

What is a luxating patella?

In the simplest terms, a patellar luxation is a dislocated knee. Canine and feline knees are built the same as human knees: ligaments attach the large thigh bone (the femur) to the lower leg bone (the tibia) at multiple points, while a tendon holds the patella, or knee cap, safely in place. 

Normally, the patella sits perfectly in a groove on the front of the femur, and it slides up and down as the knee bends and straightens. Patellar luxation occurs when the patella shifts, or luxates, out of its groove. In small dogs, this shifting generally occurs to the inside of the leg. Over time, all of that shifting causes wear and tear to the cartilage that covers the bones of the knee, resulting in degenerative joint disease. This, in turn, causes pain and decreased mobility.

What dogs are at risk?

Luxating patellas can occur in any dog, but are most common in toy and small breed dogs like Toy Poodles and Yorkshire Terriers, where the condition is considered hereditary. About half of dogs with luxating patellas are affected in only one knee, but the other half develops the condition in both knees. 

Cats occasionally have Grade I patellar luxations because their femoral grooves tend to be shallower than their canine counterparts, but the majority of patellar luxations in cats are secondary to trauma, such as a fall.

Signs +symptoms

Veterinarians classify luxating patellas into one of four grades, each with their own degree of clinical signs:  

  • Grade I patellar luxations rarely have signs and are generally found in asymptomatic dogs and cats during routine physical exams.
  • Grade II luxations are generally seen as a hitch in a pet’s gait. Affected dogs may skip while running when the patella is out of place, but quickly return to a normal gait once the patella has returned to the femoral groove.
  • Grade III and IV patellar luxations cause discomfort and affect a pet’s gait significantly. Affected pets may limp, and begin to take on a bow-legged appearance.

Patellar luxation grades

Your veterinarian will perform a physical examination to determine which of the four grades of luxation your pet has:

  • Grade I: The patella can be manually dislocated out of position, but returns to its correct position spontaneously.
  • Grade II: The patella shifts easily out of position when the knee is bent and straightened, but it returns to its normal position spontaneously.
  • Grade III: The patella luxates easily when the knee is bent and straightened, and it remains out of place.  The patella can be manually replaced into its normal position.
  • Grade IV: The patella is permanently luxated and cannot be replaced manually.

How are luxating patellas treated?

The grade of luxation will dictate the treatment option that is best for your dog. 

  • Grade I patellar luxations rarely, if ever, need treatment. 
  • Pets with Grade II luxations should be evaluated on a case-by-case basis, as some of these pets will benefit from surgery, while others do well with a short course of anti-inflammatories. 
  • Grade III and IV patellar luxations generally need surgical correction to return the pet to normal, pain-free movement.  

Not all veterinarians perform the surgeries to correct patellar luxations, and referral to an orthopedic or surgical specialist may be preferred. 

Currently, there are two surgeries that are most commonly performed to correct luxating patellas. The first involves deepening the groove in which the patella should rest. The second repositions the part of the tibia where the patellar tendon connects, thereby straightening the leg.  

Prognosis

For both non-surgical and surgical cases, the prognosis is very good. Pets should be weight-bearing by two weeks after surgery. After six to eight weeks of confinement and leash walking, they’ll be back to normal.

Pet Health

Dogs

Photo by Andre Dehne on Unsplash