The patella is the medical term for the kneecap. Luxation means that the kneecap dislocates or moves out of its normal position. A medial patella luxation (MPL) occurs when the kneecap moves out of its normal position toward the inside of the leg. Less common is the lateral patella luxation, which is when the kneecap moves toward the outside of the leg.
The patella normally sits in a deep groove located at the end of the femur (thigh bone). It glides smoothly over the cartilage within the groove during knee movement. In patients with patella luxation, this groove is usually too shallow – allowing the kneecap to “pop out.” Luxation can worsen and increase in frequency over time due to constant dislocation. The great majority of patella luxations develop as pets grow. In many breeds, it is considered a genetic or inherited trait. Most patients will have patella luxation by the time they reach maturity, but may not develop signs of problems until later in life.
How can a MPL be fixed?
There are four steps to repairing a luxated patella. Each patient is different. Your pet may require some or all of the steps for correction. The surgeon will discuss their plan for your pet and the specific steps required.
- Medial desmotomy: This step loosens the tissue on the side of the knee that is too tight and contributes to pulling the kneecap out of place.
- Lateral imbrication: This step tightens the loose tissue on the side of the knee to help keep the kneecap in the groove.
- Deepening of the shallow groove is achieved by surgically reshaping the width and depth of the groove using special instruments. This allows the patella to rest deeply within the groove and move appropriately during knee movement.
- Tibial tuberosity transposition is achieved by separating the bone to which the patella attaches from its present position. It is then moved to a new position and maintained in its new placement with bone pins. The new location keeps the tendon in proper place to prevent luxation.
Does surgery work?
At Cleveland Road, we define success as a dramatic improvement in limb function, permanent relocation of the patella, and return to normal or near normal activity. This is expected in >90% of patients.
The complication rate for these procedures is low. Infections uncommonly develop and when they do, usually resolve completely with proper treatment. Rare complications include pin breakage and migration. Anesthesia also carries a small risk of complications, however we use the same drugs and monitoring equipment that are used in humans and anesthetic complications are rare. If your pet has any medical conditions such as heart murmurs, kidney disease, breathing difficulties or liver disease, please be sure to discuss these preexisting conditions with us so that appropriate steps can be taken to ensure safety with anesthesia for your pet.
What happens after surgery?
The majority of postoperative care involves restriction of your dog’s activity. No off-leash activities are allowed. Inside the house, your pet should avoid flights of stairs and slippery floors. No running, jumping or playing is allowed for the first six weeks after surgery. When your dog is not under your direct control, he/she should be confined to a small room, cage, or crate.