What is Medial Patellar Luxation (MPL)?

MPL is a condition where a dog’s kneecap (patella) deviates from its normal position within the groove of the thigh bone (femur), moving towards the inside (medial side) of the leg. This displacement can lead to pain, lameness, and difficulty in walking or running. The severity of the condition varies, with some cases requiring surgical intervention to correct the luxation and prevent further discomfort.

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Underlying Causes of MPL in Dogs

Several skeletal factors can predispose a dog to MPL. Most commonly, there is an issue with the alignment of the hindlimb and the quadriceps muscle.

• Misalignment: If the bones in your dog’s leg don't align correctly, the patella can be forced out of its position. Dogs may have varying degrees of bending or twisting of the femur, tibia, or both.
• Shallow femoral groove: A shallower groove can prevent the patella from seating properly.
• Hip dysplasia: Abnormalities in hip development can indirectly impact knee joint positioning and the patella's stability.
• Cranial cruciate ligament disease: Rupture of the cranial cruciate ligament allows twisting at the knee joint, which can displace the patella.
• Trauma: Injuries can displace the patella, especially if the joint already has a predisposition towards MPL.

While smaller breeds tend to be more susceptible, MPL can occur in dogs of all sizes and breeds.

Treatment Strategies for MPL

Surgery for MPL is recommended when the condition is causing regular limping or skipping – this is a sign that the patella is regularly displacing. The goal of surgery is to realign the patella and stabilize the joint, allowing for improved mobility and comfort. Surgical intervention can prevent long-term joint damage and reduce the risk of arthritis associated with untreated MPL. Surgery also decreases the risk of cranial cruciate ligament rupture.

Treatment is tailored based on MPL’s severity and the dog's specific bony conformation.

• Groove deepening: The femoral groove is deepened to allow it to hold the patella more securely.
• Realigning the quadriceps: To make sure the patella tracks normally over the groove, the quadriceps must be realigned. This is usually achieved by shifting the quadriceps attachment on the tibia and securing it in a new location with pins. This is called a tibial tuberosity transposition.
• In cases with more significant skeletal malalignment, cutting and realigning the femur and/or tibia may be required. This is generally planned with a CT scan.
• Soft tissue reconstruction: Tightening the tissues on the outside of the joint helps with stability of the patella.

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Post-Procedure Care

Your pet's comfort and swift recovery are our top priorities.

At VetSurg:

• Your pet will stay overnight, to ensure pain management, monitor their initial recovery, and address any post-surgical concerns with our 24/7 on-site team.

At Home:

• Week 1-2: No running, jumping, or stair-climbing is allowed. Short leash walks to go to the toilet are ok, and these will increase over the coming weeks. The surgical site should be kept clean and dry, and the provided Elizabethan collar should stay on at all times. We will see your pet at the two-week mark to check on their progress.
• Week 3-6: The duration of leash walks can be gradually increased, and we will guide you through this. We will see your pet at 6-8 weeks after surgery for some further x-rays to monitor healing.

Potential Hurdles

Every surgery has its risks, but we're proud of our high success rate. Here's what to be aware of:

• Infection: In rare cases (~5%), infections may arise. If this occurs, we have strategies to manage and heal the infection. The implants may need to be removed after the bone has healed, but they are no longer required at that stage.
• Implant irritation: Proper aftercare and restricted movement minimize the risk of any implant issues. Irritation of the skin over the pins may be seen in a small number of animals. The pins can safely be removed after healing.
• Recurrent luxation: A very small number of dogs may have ongoing MPL after surgery. In most instances, this does not require further surgery. If it is severe enough to require another procedure, we will guide you through this.