Patella luxation is a very common orthopedic condition that we see most commonly in small and toy breed dogs. The patella is the knee cap and luxation means that it is not staying in its proper location. There are multiple factors that lead to this, including, inside displacement of the quadriceps muscle group, outside twisting of the femur (thigh bone), bowing of the femur, rotational instability of the knee joint and tibial (shin) bone deformities. Most commonly the patella will luxate to the inside of the knee. The luxations are graded from I to IV, IV being the worst.

• Grade I: The patella can be luxated on exam, and will go back to normal position as soon as pressure is removed. Luxation will rarely if never occur during everyday activity.
• Grade II: You can start to see mild deformities of the femur and tibia. The patella can be manually luxated and will usually stay there until it is placed back into its normal position.
• Grade III: The patella is luxated most of the time, but with manipulation it can be placed back into the normal position. Start seeing more severe changes of the bones.
• Grade IV: The patella is out all the time and cannot be put back into its normal location without surgery. See the most severe deformities with these cases.

Not all patella luxations require surgical intervention. In general grade III and IV luxations are going to require surgery. Grade I and II luxations we evaluate on a case by case basis depending on clinical signs, history and comfort of the animal.

Surgery most commonly consists of up to 4 techniques, medial fascial release to release the pull on the patella towards the inside of the knee, trochlear manipulation to deepen the groove that the patella normally sits in, anti-rotational suture to prevent inside rotation of the tibia (which can cause the patella to luxate), tibial tuberosity transposition (TTT) to move the muscle attachment of the quadriceps and align the patella up with the trochlea better and lateral imbrications which will pull the patella more to the outside of the knee joint. We do not use all of these techniques every time we do the procedure, but we look at each case at the time of surgery and decide what needs to be done for the changes that are observed at that time. There are also some more aggressive techniques to use on cases that do not respond to these options.