Patella luxation is the dislocation of the kneecap (patella) from its natural groove in the femur (thigh bone). This abnormality can be found in any size or breed of dog, but it is most commonly found in toy or miniature breeds. Although usually a congenital (being present at birth) defect, patella luxation can also be the result of trauma.

Patellas in correct position

Normally, when the leg is flexed and extended, the patella should glide up and down in the trochlear groove at the end of the femur. This groove should ideally be deep enough for the patella to fit comfortably into it. When the tendons, muscles and bones are properly aligned, the result is a stable knee joint. However, when these structures are improperly aligned, the major muscles of the thigh pull towards the inside or medial aspect of the leg, applying abnormal stress to the knee joint. The resulting forces pull the patella out of place, usually toward the inside of the leg. As the patella is allowed to pop in and out of place, the normal gliding motion of the cartilage within the joint is interrupted. The cartilage becomes degraded, leading to rubbing of bone against bone and eventually arthritis.

The degree of severity of medial patella luxations is classified into four grades:

Grade I: The patella can be manually luxated when the leg is extended, and the patella is pushed over but will go back into place when released.

Grade II: The patella sits loosely in its normal position but will luxate medially when the leg is flexed. Reduction is possible with manipulation. A “hopping” gait is generally noted here.

Patella luxating medially Grade III: The patella is displaced medially most of the time but can be reduced manually when the leg is extended.

Grade IV: The patella is displaced medially all of the time and cannot be manually reduced. A hunched over stance is often noted, and some dogs may even appear bowlegged.

Patellas pulled medially

Surgical correction involves stabilizing and repositioning the patella in the trochlear groove of the femur, which often has to be surgically deepened. Addressing this condition early reduces the chances of developing arthritis. No surgery can reverse arthritis that is already present, but our aim is to provide a good return to function.

Recovery time for this procedure takes 6 to 8 weeks. The first 2 weeks there is no running, jumping, rough play or excessive stairs: only short leash walks to urinate and defecate. At the end of 2 weeks, short 5 to 10 minute leash walks one to two times a day can be started. We re-evaluate your pet’s progress at 4 weeks. If everything is going well, there is a gradual increase in activity over the next 3 to 4 weeks. The last 2 to 3 weeks are a gradual return to normal activity.