MPL surgery is a procedure to correct medial patellar luxation in dogs, a condition where the kneecap slides out of its normal groove toward the inside of the leg. It’s one of the most common orthopedic surgeries in dogs, especially small breeds, and clinical outcomes improve in over 90% of dogs who undergo it. The surgery repositions the kneecap and reshapes the knee joint so the patella tracks properly when your dog moves.
What Medial Patellar Luxation Actually Is
Your dog’s kneecap (patella) normally sits in a groove at the bottom of the thighbone and glides up and down smoothly as the leg bends and straightens. In medial patellar luxation, the kneecap pops out of that groove and shifts toward the inner side of the leg. When this happens, your dog may suddenly skip a step, hold the affected leg up for a few strides, or walk with a persistent limp. Some dogs learn to kick the leg out to pop the kneecap back into place on their own.
Vets grade patellar luxation on a scale from 1 to 4 based on how easily the kneecap dislocates and whether it stays out of position:
- Grade 1: The kneecap can be manually pushed out of the groove but pops back on its own. Dogs often show little or no lameness.
- Grade 2: The kneecap slips out during normal movement and sometimes stays out until the dog straightens the leg or a vet repositions it. Limping comes and goes.
- Grade 3: The kneecap sits outside the groove most of the time. It can be pushed back in manually, but it doesn’t stay.
- Grade 4: The kneecap is permanently dislocated and cannot be repositioned by hand. The groove itself is often shallow or flat.
When Surgery Is Recommended
Not every dog with a luxating patella needs surgery. Grade 1 and grade 2 cases can sometimes be managed conservatively with weight management, controlled exercise, and joint supplements, as long as your dog isn’t limping regularly and arthritis is minimal. But if your dog shows intermittent or persistent lameness at any grade, surgery should be considered.
Grade 3 and grade 4 luxations need surgical correction. At these stages, the kneecap is out of place most or all of the time, which distorts the pull of the thigh muscles and accelerates joint damage. In young, growing dogs, early surgery is also recommended to prevent the abnormal kneecap position from warping developing bone.
What the Surgery Involves
MPL surgery isn’t a single technique. Surgeons typically combine two or three procedures in one operation, tailored to the severity of your dog’s condition.
The most common combination includes deepening the groove where the kneecap sits (called a trochleoplasty), repositioning the point where the kneecap tendon attaches to the shinbone (tibial tuberosity transposition), and tightening the soft tissues on the outer side of the knee (lateral imbrication). Groove deepening gives the kneecap a deeper channel to ride in. Moving the tendon attachment corrects the alignment of the entire mechanism so the kneecap is pulled straight rather than at an angle. Tightening the outer tissue acts like a reinforced wall that keeps the kneecap from slipping inward again.
In some cases, the surgeon may also release tight tissue on the inner side of the knee that’s pulling the kneecap out of alignment. The specific combination depends on the grade of luxation, your dog’s size, and how much the bone structure has been affected.
Success Rates and Risks
MPL surgery has a strong track record. More than 90% of dogs show clinical improvement after the procedure. In one study of 119 surgically treated knees, about 52% returned to full function and another 43% had acceptable function, meaning the dog used the leg well with only minor limitations. Less than 5% had unacceptable outcomes.
Re-luxation, where the kneecap slips out again after surgery, occurred in about 6% of cases in that same study, and none of those dogs required a second surgery to fix it. Minor complications, including low-grade re-luxation, affected about 14% of knees. Major complications requiring additional surgery occurred in roughly 9% of cases.
Dogs that have both knees operated on in a single session actually showed the highest rate of full function at 77%, compared to about 52% for dogs that had just one knee done. This may reflect case selection (dogs healthy enough for bilateral surgery tend to do well overall), but it also means that having both knees corrected at once is a reasonable option when your vet recommends it.
What Recovery Looks Like
Recovery from MPL surgery takes about 8 weeks of structured activity restriction, followed by a gradual return to normal life. The first two weeks are the most restrictive. Your dog should be confined to a small area, with outdoor time limited to 5 to 10 minutes on a leash for bathroom breaks only. Applying a cool compress over the knee incision 3 to 4 times a day for the first week helps manage swelling.
During weeks 3 through 6, you can start reintroducing short leashed walks of about 10 minutes, three times daily, gradually increasing to 15 to 20 minutes. This is also when gentle rehabilitation exercises become important. Passive range of motion work (slowly bending and straightening the ankle, knee, and hip about 10 times per session, two to three times a day) helps prevent stiffness. Light massage of the thigh muscles before and after exercise keeps blood flowing to the area.
By weeks 7 and 8, most dogs are approaching full activity. Walk lengths increase to 20 to 30 minutes, and you can begin allowing stair climbing under supervision. Many dogs are back on a leash for about two months total before off-leash activity is gradually permitted.
Home Exercises That Help
Two simple exercises can make a real difference during recovery. “Puppy squats” involve having your dog sit down and immediately stand back up, which rebuilds the thigh muscles that stabilize the kneecap. Start with 5 to 7 repetitions, three to four times daily, and work up to 10 to 20 reps by weeks 6 through 8.
Figure eights are another useful exercise. Walk your dog in a figure-eight pattern with each loop about 10 to 15 feet across. This forces controlled weight shifting onto the surgical leg during turns. Start with about 10 repetitions per session and increase over time. By weeks 6 to 8, you can also introduce slow, controlled hill walks with the surgery leg on the downhill side, which loads the leg in a way that builds strength without high impact.
Moist heat applied for 5 to 10 minutes before exercise sessions (starting around week 2) helps loosen the joint and makes the exercises more comfortable for your dog.
How Much MPL Surgery Costs
In the United States, most MPL surgeries cost between $1,500 and $3,500 per knee. If both knees need correction, the total typically falls between $3,000 and $7,000 depending on the complexity and where you live. Urban referral hospitals tend to charge $3,500 or more per knee, while general veterinary clinics in smaller towns may be closer to $1,500 to $2,000. A straightforward grade 1 repair in a small dog at a general practice can come in under $2,000.
These figures generally cover the surgery itself, anesthesia, and basic post-operative care, but diagnostics (X-rays, bloodwork), medications, follow-up visits, and any physical rehabilitation add to the final bill. If your dog needs both knees done, ask your surgeon whether a single-session bilateral procedure is appropriate, since it can reduce the total cost of anesthesia and facility fees compared to two separate surgeries.
Long-Term Outlook
Most dogs do well long-term after MPL surgery. Some degree of arthritis in the affected knee is expected over time, even after a successful repair. Research on similar knee surgeries in dogs shows that while arthritis progresses gradually in the months and years after surgery, it doesn’t necessarily translate to worsening lameness. Weight-bearing function improved within the first six months after surgery and held steady for at least three years in one study, despite visible arthritis progression on X-rays.
Keeping your dog at a healthy weight is one of the most effective things you can do to protect the repaired knee long-term. Extra body weight increases the load on the joint with every step and accelerates cartilage breakdown. Maintaining the strengthening exercises you learned during recovery, even informally through regular walks and varied terrain, helps keep the muscles around the knee strong enough to compensate for any early joint changes.