Luxating Patellas in Dogs and Cats
Written by Small Door's medical experts
Luxating patellas in dogs and cats are a common orthopedic condition that can cause lameness. Luxation occurs when the patella, or kneecap, slips in and out of the groove in the femur where it should normally reside. When this happens, you may notice changes to your pet’s gait, including lameness and signs of pain, however some cases can be asymptomatic. Depending on the grade of patella luxation and clinical symptoms, it is generally treatable with orthopedic surgery. Occasionally, a luxating patella can lead to other conditions, like torn cruciate ligaments, which is why it is important owners take the condition seriously and consult with their veterinarian.
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A luxating patella is when a dog or cat’s kneecap moves out of place or momentarily dislocates. Luxation occurs when the patella, or kneecap, slips in and out of the groove in the femur where it should normally reside. When this happens, you may notice changes to your pet’s gait, including lameness and signs of pain, however some cases can be asymptomatic.
In a normal, healthy animal structure, the patella (or kneecap) sits under a ligament called the patellar ligament, which attaches to the large thigh muscles to a point on the tibia (or shin bone). However, in the case of a luxating patella, the point of attachment for the patellar ligament is not on the center of the shin bone, so when the thigh muscles move and contract, the patella is pulled to the inside of the knee. After an extended period of time, the femur wears down allowing the patella to easily dislocate.
Most commonly, owners will notice their dog running about and suddenly skip or run on three legs then quickly return back on all fours as if nothing happened. When this happens, the patella has typically luxated.
Luxating patellas can be caused by an injury. However, they are often hereditary, with some breeds being predisposed to it over others.
Luxating patellas can be either medial (called a MPL where the kneecap slips towards the midline of the pet) or lateral (called a LPL where the kneecap slips away from the pet).
Small breeds or “toy” dogs are often susceptible to patellar luxation. These types of dogs often include:
Cavalier King Charles Spaniel
Jack Russell Terrier
When large breed dogs can experience patellar luxation, this is typically due to an injury, over-exertion, or other structural problems like hip dysplasia. Large breed dogs that are commonly known to have patellar luxation include:
There are also four grades of luxation, with 1 being the mildest, and 4 the most severe.
Grade 1: The patella can be manipulated out of its groove, but returns to place on its own.
Grade 2: The patella moves in and out of the joint more readily, occasionally popping out on its own, but also returns to normal position easily.
Grade 3: The patella is more often out of its groove than in the groove, but it can be manipulated back to normal position.
Grade 4: The patella permanently sits out of its groove and cannot be manipulated back to its normal position.
Symptoms of luxating patellas in dogs and cats can vary depending on the grade of the luxation.
Common signs of luxating patellas include:
Carrying the limb up for a few steps (skipping)
Shaking or extending the limb
Bow-legged appearance (where the legs curve outwards at the knees)
“Knocked-in” knee appearance (where the legs curve inwards at the knees)
In mild cases, you may not notice any changes in your pet’s gait. This condition is often an incidental finding discovered during physical exams, especially in young puppies. In other cases, particularly more serious ones, symptoms are more obvious. You might notice your dog or cat carrying their leg up for several steps, giving them the appearance of skipping. Before they resume walking normally, they might also shake or extend the limb as they try to pop the patella back into place, which allows them to fully extend their leg again.
Young puppies with severe medial patellar luxations may have a bow-legged appearance. This will only worsen with age and growth. Large breed dogs, on the other hand, may have a “knocked-in” appearance with lateral patellar luxations. Over time, arthritis and other complications can lead to general lameness, further complicating the luxation.
Cats and dogs develop luxating patellas for several reasons, including genetic predispositions and injuries.
Common causes include:
Muscle atrophy or tightness
Improper patellar ligament length
Luxating patellas are among the most common orthopedic problems in dogs. In some cases, a traumatic injury to the knee causes patellar luxation. In most cases, however, the exact cause is unclear, and is likely the result of multiple factors including abnormal hindlimb skeletal conformation or malformation, and subsequent abnormalities of the ligaments, tendons, and muscles that can all lead to patellar luxation.
As the condition can be hereditary, dogs and cats with luxating patellas should not be bred.
Your veterinarian can diagnose a luxating patella during a full physical examination. During the exam, they will palpate the knee to determine if any instability is present. Depending on the severity and clinical symptoms, follow-up diagnostics may be recommended.
These diagnostics may include palpating the knee while your dog or cat is sedated to see if there is damage to the ligaments; radiographs of your pet’s pelvis, knee, and tibias to examine bone structure; and even advanced imaging like CT scans. CT scans are useful in severe cases if surgery will be necessary, as they help veterinary surgeons best plan how to correct the shape of the femur or tibia.
How a luxating patella affects your pet’s overall health often depends on the grade of luxation and if both knees or just one are affected.
Some pets can go for years or a lifetime without being too bothered by this condition. However, luxating patellas often lead to other injuries like torn cruciate ligaments or arthritis from how the leg is altered and abnormal weight distribution on the leg.
Low grades of luxating patellas can be treated non-surgically. Others will require surgical correction to avoid pain, lameness and further damage to the knee joint. Grade 1 luxating patellas may not require surgical correction; however, your veterinarian will monitor the condition in case it worsens over time. Treatment options for grade 2 will depend upon whether your pet is symptomatic. Asymptomatic grade 2’s are usually treated non-surgically, as in grade 1. Repeatedly symptomatic grade 2 and grade 3-4 usually require surgical correction.
Is there a cure for a luxating patella in dogs and cats?
Luxating patellas can be corrected with surgical intervention. During surgery, the surgeon may use several strategies to repair the luxation, depending on the underlying conformational abnormalities. They may correct the point of attachment for the patellar ligament, deepen the groove of the femur, tighten the joint capsule, and/or place an implant on the inside of the knee to prevent the patella from slipping.
Is a luxating patella in dogs and cats contagious for humans or other pets?
Luxating patellas are not contagious. However, as the condition may be genetic, dogs and cats with patellar luxations should not be bred.
What is the cost of treating a luxating patella in dogs and cats?
The cost for treating luxating patellas will vary depending on the course of treatment. Non-surgical cases of luxating patellas will cost less to treat than surgical ones. Diagnostics can cost hundreds of dollars, and surgery itself can be several thousand dollars, as it requires a board-certified orthopedic surgeon. However, the risks of choosing not to undergo surgery can include complications like cruciate ligament tears, formation of debilitating arthritis, and other surgical conditions, resulting in even more expensive treatments and chronic pain for your pet.
The cost of treatment will also depend on whether or not both limbs are affected, and any post-surgical complications. Speak to your veterinarian about any financial concerns, and be sure to look over the estimate carefully.
Low grades of patella luxation require careful monitoring, both during annual examinations with your veterinarian, and at home, as any signs of discomfort or progression in symptoms may change your veterinarian’s clinical recommendations.
If your pet does require surgery, most pets recover relatively quickly when the surgery is performed by an experienced, board-certified veterinary surgeon. If your pet requires additional surgery for another knee, plan for a longer total recovery time. They’ll need to avoid exercise during the recovery period, and your veterinarian will provide anti-inflammatory medications and painkillers to help manage their pain.
Omega fatty acids are a useful, all-round supplement for any pet with skeletal problems. There is substantial scientific evidence that marine sources of omega-3 fatty acids provide anti-inflammatory benefits to the joints, which can help to prevent damage to our pets’ delicate joint cartilage.
Unfortunately, if your pet already has arthritis associated with the joint, the arthritis may persist or even worsen despite surgery. Early diagnosis and intervention is the key to a successful outcome. Arthritis can be managed with anti-inflammatory pain medications, joint supplements (such as glucosamine/chondroitin, which can help reduce pain, and the previously mentioned omega fatty acids), weight loss, and/or prescription diets designed with ultra-high levels of omega fatty acids.
Not all supplements are created equal and at Small Door, we recommend the following brands, both for their excellent levels of quality control, in addition to appropriate levels of omega 3 concentrations:
Vetoquinol Triglyceride Omega (Can be purchased at Small Door Veterinary)
In rare cases, recurrence of luxating patellas is possible, even after surgery. The risk increases with the grade of luxation, with grade 4 patellar luxations carrying a higher risk of recurrence.
Can you walk a dog with a luxating patella?
Pets suffering from low grade luxating patella can still go out for walks and enjoy their normal activities, however we recommend you try to prevent them from jumping up and down, as this puts a lot of stress on the knee joint. Placing ramps or steps strategically in your home can help your pet to get onto the couch or bed while avoiding a large jump.
Most cases of luxating patellas cannot be prevented, as they are either genetic or the result of a traumatic injury. Keeping your pet fit and healthy, however, will improve their chances of a swift recovery and reduce the risk of complications. Obese pets, for instance, are at an increased risk of other skeletal conditions.
Is there a vaccine for a luxating patella in dogs and cats?
No, luxating patellas are an orthopedic condition and there is no vaccine for them.
A luxating patella in cats or dogs can be a serious but treatable orthopedic condition, where the kneecap moves out of place. Whether the luxated patella is the result of an injury or a genetic predisposition, understanding the risks associated with the condition will help you make the best choices for your pet’s wellbeing and recovery.