Medial Luxating Patella (MLP)

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Medial Luxating Patella (MLP)

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The medial luxating patella, commonly called trick knee, is a prevalent problem in toy breed dogs. An owner typically notices a little skip in the dog’s step. The dog may even run on three legs, holding one hind leg up, and then miraculously be back on four legs as if nothing has

happened. In fact, something has happened: the kneecap (patella) has slipped out of the smooth groove in which it normally rides up and down. The patella, or ‘kneecap,’ is normally located in a groove on the end of the femur (thigh bone) just above the stifle (knee). The term luxating means ‘out of place’ or ‘dislocated.’ Therefore, a luxating patella is a kneecap that moves out of its standard location. Then, suddenly, they will be back on all four legs as if nothing happened! This typically means that the kneecap has slipped medially (towards the opposite leg, as opposed to laterally, which would be away from the dog entirely). With the patella dislocated medially, the knee cannot extend properly and stays bent. When the kneecap dislocates, it stops the knee from bending, causes a limp, and rubs past the bone as it slips, which can cause pain and arthritis over time.

Grades of MPL:

Patella luxation can affect one or both knees and varies from grade 1 to 4:

Grade 1: The kneecap is loose but stays in the correct place when your dog

moves around. It will dislocate if forced by your vet but immediately returns when released.

Grade 2: The kneecap occasionally dislocates but usually returns by itself;

symptoms range from mild to moderate depending on how regularly the kneecap dislocates.

Grade 3: The kneecap is permanently dislocated, can be pushed back into place by your vet, but slips straight out again when they let go.

Grade 4: The kneecap is permanently dislocated and is impossible to push back into place.


Your vet will carefully feel your dog’s knee and perform various tests to check the stability of the kneecap. They will also check the cruciate ligaments because cruciate disease is

common in dogs with patella luxation. Some dogs may need x- rays for a complete diagnosis.


The course of treatment will greatly depend on the grade of their patella luxation and their symptoms. If your dog only limps every now and again, it might be possible to manage their patella luxation with physiotherapy and exercise control. However, if your dog limps regularly or is in pain, surgery might be the best option.

Physiotherapy and Surgery

Most mild cases of patella luxation (grade 1&2) can be managed without surgery. Physiotherapy and controlled exercise help build-up the leg muscles and stop the kneecap from slipping. Surgery is necessary for some dogs with patella luxation, especially if it is severe (grade 3&4). There are a few different surgical options your vet may recommend.

Pain relief

Most dogs with patella luxation experience pain at some point

during their life. Your vet will be able to prescribe pain relief such as NSAID’s to give

as necessary.


Keeping your dog at the correct body weight reduces pressure on their joints, which can help with patella luxation and arthritis in the future. Check your dog’s weight and body condition regularly, and make sure you feed them the right amount to keep them at a healthy weight.

Sensible exercise

Once your dog has recovered, they will be able to exercise more or less normally. To minimize

the risk of further injury, it’s best to avoid strenuous activities such as chasing, jumping, and running up and down stairs/on uneven ground.

Supportive therapy

Your vet might recommend hydrotherapy or physiotherapy to help with your dog’s ongoing recovery.

Susceptible Breeds

Patella luxation is more common in certain breeds, especially toy and small breeds. This is often is because these breeds have bow-shaped legs or a shallow knee a groove that doesn’t hold the kneecap in place.

Breeds prone to patella luxation include:

  • Miniature and toy poodles
  • Yorkshire terriers
  • Pomeranians
  • Pekingese
  • Chihuahuas
  • Boston terriers
  • Jack Russell Terrier
  • Staffordshire Bull Terrier

Contact your vet if you suspect your dog may have patella luxation. The sooner it’s treated, the better your dog’s outlook, and the less chance of arthritis in the future.