Patellar Luxation – or dislocated kneecap – is a fairly common condition in some breeds of dog, especially smaller toy breeds. We have combined some freely available information from the Veterinary Partner website* to answer many of the questions that we get asked about this common condition.
Knee with medial luxating patella. Instead of riding up and down normal groove (yellow arrow) patella is off to the side (yellow circle).
What is Patellar Luxation?
Patellar luxation is a condition where the kneecap (patella) has slipped out of the smooth groove in which it normally rides up and down. It has slipped medially, which is to say towards the opposite leg, as opposed to laterally, which would be away from the dog entirely.
With the patella dislocated (or luxated) medially, the knee cannot extend properly and stays bent. With luck, the patient will be able to slip the kneecap back where it belongs and be back to normal in only a few steps.
For some dogs, getting a kneecap back where it belongs and normal extension of the rear leg is only attainable with surgical correction.
What Breeds Are Most Prone to Patellar Luxation?
Some breeds have a higher incidence than others. Breeds known to have this condition include: Affenpinscher, Brussels griffon, Chihuahua, English toy spaniel, Greyhound, Japanese spaniel, Maltese, Manchester terrier, Miniature pinscher, Papillon, Pekingese, Pomeranian, Poodle, Pug, Shih tzu, Silky terrier, and Yorkshire terrier.
Is Patellar Luxation Painful?
I have clients whose stomachs churn when they hear that patellar luxation is a slipped or dislocated knee. I can’t blame them, because it does sound awful in human terms! But this condition can vary in severity, and in its mildest form is not terribly painful for the dog. With a grade one dislocation, 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.
It’s clearly not a good thing to have a knee cap out of place; the weight-bearing stress of the rear leg is altered which, in time, leads to changes in the hips, long bones, and ultimately arthritis. How severe the changes are depends on how severe the luxation is (i.e., the grade described below) and how long that degree of luxation has been going on.
In time, the legs will actually turn outward with its muscles turning inward, making the dog bow-legged. The luxation is not considered a painful condition but after enough time and conformational change, arthritis sets in, which is indeed painful.
What Are The Four Grades of Patellar Luxation?
Grade 1: The patella luxates with manual pressure and returns spontaneously. Dogs with Grade 1 luxations do not typically require surgical repair.
Grade 2: The patella luxates with flexion and extension of the joint, but returns to the trochlear groove spontaneously. Some lameness may be present. Whether or not surgery is required depends on several factors: how often lameness is a problem, and how long lameness lasts when it is a problem. If the ridge of bone on the inside of the knee wears down, the Grade 2 will progress to Grade 3 and surgery can be preventive.
Grade 3: The patella luxates with flexion and extension of the joint, but can be reduced manually, although it will not stay there. Considerable lameness exists. Dogs with Grade 3 or 4 luxations definitely should have surgery.
Grade 4: The patella is permanently luxated to the medial side. The limb or limbs are unable to extend and the animal walks balancing its weight on the forelimbs.
What Surgical Procedures are Available?
There are several different types of procedure to correct the condition. Here at Compassionate Animal Care, we will typically perform surgery in-house on small dogs with mild Grade 1 or 2 conditions. For more complex Grades, we refer them to a trusted Orthopedic surgeon.
Should Both Knees be Repaired at the Same Time?
X-ray of a dog with a normal knee. Photo by MarVistaVet
About 50% of affected dogs have both knees involved. For those with both knees affected some surgeons feel that doing one leg at a time, eight weeks or more apart, is beneficial as the patient will have one good rear leg upon which to walk. If the patient is very young (under age one year) it may be a good idea to do both legs at the same time so as to prevent conformational problems in the leg not operated on first.
What Post-Operative Care is Required?
If imbrication was the only procedure, expect three to four weeks of confinement. If any of the other procedures above were utilized, expect more like six to eight weeks of confinement depending on the surgeon’s preference.
During this time easy walking (no running or jumping) is helpful. The dog should be using the leg by two weeks post-operatively though some dogs must be retrained to use the leg after surgery.
Physical therapy is in order if the dog is not using the leg after one month.
I’ve Noticed Symptoms. What Should I Do?
The first thing to do with any medical concern you have with your pet is to consult your veterinarian. At the appointment you can discuss any symptoms you have noticed, and have the dog physically examined to determine the severity of the condition.
Of course, if you have any questions, please do not hesitate to contact Compassionate Animal Care at 480.774.6995.
*Source: https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952566 and https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952398
