Everything You Need to Know About Luxating Patella in Dogs

What causes dogs to have Patellar Luxation?

Put simply, a luxating patella is the medical term for when a kneecap “pops out” or moves from its normal groove in the lower part of the femur. 

The condition can range in severity. Some dogs may tolerate it for their entire lives. Others may develop arthritis that then exacerbates the problem considerably, leading to decreased mobility and joint pain. 

Read on to find out more about patellar luxation, how it gets treated, and what you can do to help a dog that suffers from it. 

What is Luxating Patella?

The knee joint connects the thigh bone or femur and the shinbone or tibia. The kneecap or patella normally sits in the trochlear groove at the end of the femur. The term “luxating” means dislocating.

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Should the kneecap of your dog move out of position, you might notice an odd skipping motion in their step or see your dog running on 3 legs. Then, all of a sudden, the kneecap might pop back into normal position and they will be back on all 4 legs as though nothing happened.

The kneecap can move to several different places within the knee joint. This will depend on which structures have become loose or damaged. More often than not, the movement or luxation of the patella is medial, i.e. towards the body.

What Causes Patellar Luxation?

As the muscles in the thigh begin to contract, the force gets spread through the knee or patellar ligament. That pulls on the shin bone. This leads to a straightening of the knee. The patella slips up and down in its groove, helping to hold the patellar ligament in place throughout the movement.

In certain dogs, particularly those with bowlegs, the patella can luxate. This is due to the point of attachment of the patellar ligament not being in the center of the shinbone. In these instances, it is nearly always too far toward the inside of the leg or the middle of the body. 

When the thigh muscles contract, the force on the patella pulls it to the inside of the knee. After months or even years of this kind of abnormal movement, the inner side of the groove in the femur can wear out. When this happens, the patella is free to dislocate.

A Genetic Predisposition

A lot of small and toy breeds of dogs can be genetically predisposed to a luxating patella. These include Yorkshire and Boston terriers, Bichon Frise, Papillon, Pekingese, Chihuahuas, and French Poodles.

Dogs with patellar luxation tend to have a problem that they were born with or have developed over time. There isn’t therefore much you can do to prevent it. Keeping dogs active and managing their weight can help.

Patellar luxation can make it more likely the knee will experience other issues, particularly torn cruciate ligaments.

The Different Stages of Luxating Patella

There are 4 medical grades of luxating patella:

Grade 1: 

It’s possible to luxate the patella manually although it will quickly regain its usual position when released. This could be an incidental finding in some dogs.

Grade 2: 

When the patella luxates, it regains its natural position with manipulation. The patella can also become dislocated manually. This would happen by extending the joint and shifting the foot in the direction of the dislocation. The luxation may often resolve itself when the joint gets flexed.

Grade 3: 

The patella is in a state of continuous luxation. It is, however, possible to put it back in a normal position manually. The patella will resume luxation once it gets released from manual reduction.

Grade 4: 

The patella becomes permanently luxated and it is not possible to return it to its normal position.

One or both kneecaps may luxate in affected dogs, occasionally to a different degree. Around 50 percent of affected dogs have both luxation problems in both knees.

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The Diagnosis and Treatment for Luxating Patella

Diagnosis is often (but not always) relatively straightforward. Your vet will carry out a physical examination. They will be able to see how easy it is to move the patella out of position and whether doing so causes them discomfort. Your vet may also take X-rays to check for any underlying damage to the knee joint or to the structures that surround it.

In many cases, careful management is successful in treating moderate or mild cases of patellar luxation. Treatment may include exercises, weight loss, supplements, and medication such as anti-inflammatories and pain relief. 

Your vet might recommend surgery if: 

  • Your pet has recurrent or persistent lameness 
  • If other secondary knee injuries happen along with the luxating patella
  • If your pet falls into the Grade 2-4 categories 

A surgical repair is a moderately complex procedure, and usually involves some of all of the following 3 steps:

  1. The place where the patellar ligament attaches itself to the shin bone gets moved to its ideal location.
  2. Your vet will deepen the groove in the femur to make it easier for the patella to remain in place.
  3. The capsule surrounding the joint gets tightened up. As the patella luxates, the joint capsule extends. Tightening it will help stop the patella from luxating. Sometimes, vets will use an implant on the inside of the knee so that the patella can’t slip over it.

The recovery period after surgery is often not too complicated, particularly with the right pain management.

The Prognosis After Treatment

The success rate of sorting out patellar luxation through surgery is 85 to 95 percent when it gets performed on younger dogs.

The prognosis for older dogs with chronic patellar luxations is less good. Early detection and treatment tend to produce more favorable outcomes. A luxating patella can happen at the same time as an anterior cruciate ligament tear in bigger dogs.

If your vet carries out surgery before arthritis sets in or another knee injury crops up, the prognosis is far better. Once arthritis has developed in the knee joint, your dog might experience pain in the leg. 

The higher the grade of patellar luxation, the greater the likelihood of recurrence after surgery. Patellar luxation can cause pain in dogs that have grades 2-4 of a luxating patella. The prognosis is typically better for dogs with lower grades.

Get in Touch with a Vet Today

If you think your dog may be suffering from patellar luxation, talk to one of our team of experts today. Book a timeslot here.

Our highly-experienced vets are there to help and offer advice about the best way forward for you and your pet to deal with luxating patella in dogs or other knee issues.

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