Luxating Patella: A Knee Problem in Dogs

Patellar luxation or Luxating patella is a condition where the kneecap (patella) moves out of its normal position.  Luxating patella is one of the most common knee joint abnormalities of dogs, but it is only occasionally seen in cats.  It may affect one or both of the knees.   In some cases, it moves (luxates) towards the inside of the knee, and in other cases, it luxates towards the outside of the knee.  Luxation to the inside of the knee is the most common form seen; it is most commonly seen in the small or miniature breeds of dogs such as Lhasa apso, shih-tzu, Poodles, Maltese, Yorkies, and Chihuahuas.  Luxations towards the outside of the knee are seen less frequently.  It can be present in many breeds but is seen especially in Newfoundlands.

There are four grades of patellar luxation:

  • Grade I- the kneecap can be manually luxated but the kneecap returns to its normal position when the pressure is released -no surgery required.
  • Grade II- the kneecap can spontaneously luxate out of position with just normal movement of the knee-Minor surgery may be needed only if the dog is limping frequently.
  • Grade III- the kneecap remains luxated most of the time but can be manually reduced into the normal position. -corrective surgery is recommended with a Tibial tuberosity transplant.
  • Grade IV- the patella is permanently luxated and can not be manually repositioned -corrective surgery is recommended with a Tibial tuberosity transplant.

What are the risks?

Dogs frequently start with a Grade I or Grade II and worsen over time to a Grade III or IV. Many people are not aware their pet is affected, but a luxating patella can cause pain.  Owners may see the pet limp on a rear leg, or they may see them shake a rear leg to try to snap the kneecap back into place.

Uncorrected, the patellar ridges will wear, the groove will become even shallower, and the dog will become progressively lamer. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility. Therefore, a good evaluation needs to be done by your veterinarian early in the condition to prevent long-term arthritic crippling.

A serious consequence of patellar luxation is arthritis and it also predisposes the dog to a rupture of a ligament inside the knee called the anterior cruciate ligament (ACL).  ACL ruptures are very painful, at least initially, and usually, the dog doesn’t bear weight on the affected leg. Surgery is indicated for any case that is causing lameness or pain.  Owners may also elect corrective surgery as a way to prevent an ACL.

Treatment for Luxating Patellas

As would be expected, medical therapy has little corrective ability in this disorder and surgery is therefore required and is the treatment of choice. A surgical treatment is not necessary for every individual with this condition.

Surgery can alter both the affected structures and the movement of the patella. The groove at the base of the femur may be surgically deepened to better contain the kneecap. This procedure is known as a trochlear modification. The kneecap itself may be “tied down” laterally (on the outside) to prevent it from deviating medially (toward the inside). This is called a lateral imbrication. The bony protuberance at the site of the attachment of the quadriceps tendon on the tibia may be cut off and then re-attached in a more lateral position. This is termed a tibial crest transposition. At Allwest, we perform all of these procedures depending upon the individual case and grade/severity of the condition. The animal should respond quickly after surgery and is usually completely recovered within 20-50 days, depending upon the procedure.