Patella luxation is a common problem, especially in small dogs, but it can cause issues in dogs of any size. Also referred to as slip knee, patella luxation can cause issues like cartilage damage, inflammation, pain, and even ligament tears. But by knowing how to recognize the signs of patella luxation in a dog and understanding what can be done about it, pet owners may be able to help protect their dog's knees.
What Are Luxating Patellas in Dogs?
Luxating patellas are knee caps that slip out of the groove that they are designed to stay in. The femur, which is the large upper leg bone, has a groove down the middle that the knee cap and its associated ligaments sits in. With patella luxation, the knee cap slides out of this groove in the leg bone, often because the groove is shallower than it should be. This problem can be evident in puppies as young as eight weeks old. Oftentimes, the patella will slip out and then back in, but in other cases, it will pop out and not want to go back into the groove. Luxations can occur either medially (towards the inside of the knee) or laterally (towards the outside of the knee) and in one or both legs.
Depending on the type or severity, a dog's patella luxation will be assigned a grade between one and four based on the grading system of the Orthopedic Foundation for Animals (or OFA).
- Grade 1: The patella is able to be moved out of the groove but easily pops back by itself. This is especially common in small breeds like Yorkshire terriers, Chinese crested, and Pomeranians.
- Grade 2: The patella moves out of the groove in the knee frequently and may cause the dog to hold the affected leg up on occasion but it can be easily moved back to the correct location and the dog still often walks on it. Because the patella slips in and out of the groove so often, trauma in the knee can occur over time.
- Grade 3: The patella is out of the knee groove most of the time and the tibia, one of the lower leg bones, is moderately twisted. The groove where the patella should sit is very shallow. Some dogs may continue to use the leg but in an abnormal position.
- Grade 4: The patella is permanently out of the knee groove, and the tibia is severely twisted. The groove where the patella should sit is non-existent or even convex instead of concave. The dog will usually hold the leg up.
Signs of Luxating Patellas in Dogs
A dog with a patella luxation will often hold up the affected hind leg when walking. This may occur for a few strides after which they use the leg normally. They may also bear weight on the leg while it is bent at an unusual angle. Sometimes the knee cap is able to be visualized moving back and forth in a dog.
If a chronic luxating patella has caused knee trauma over time, a dog may show signs of pain in their knee. Crying, licking at the knee, limping, and an unwillingness to walk on the affected leg can all be seen.
Causes of Luxating Patellas in Dogs
Almost all dogs diagnosed with luxating patellas were born with a defect in their knee. It may not become apparent until later in life, but the OFA suspects that most dogs have inherited this problem.
The other cause of luxating patellas is trauma. A dog that was hit by a car or had some other sort of injury affecting their knee could develop a patella luxation.
Treatment of Luxating Patellas in Dogs
Depending on the severity of the patella luxation, your veterinarian may recommend that surgery be performed to hold the patella in its appropriate location. There are several different surgical procedures that can accomplish this with the best option depending on the specifics of the dog's case. Since knee surgeries are major procedures, if the patella luxation is only a grade one or even a mild grade two, surgery may not be discussed or recommended right away. If a dog with patella luxation is showing signs of pain, has developed the luxation due to knee trauma, or has difficult walking, then surgery will be needed to correct the problem.
While there is no way other than surgery to correct a patella luxation, you can support your dog's knee health through the use of joint supplements. Supplements can help the cartilage stay healthy and decrease inflammation in the joints, so even if a dog only has a grade one patella luxation; it's a good idea to do what you can to help support their knees. Pain relief and other treatments may also be necessary.
How to Prevent Luxating Patellas in Dogs
Other than doing what you can to prevent a major trauma, like getting hit by a car, from occurring to a dog, the only real way to try and prevent luxating patellas is to avoid using a dog with known patellar luxation for breeding purposes. Since most luxating patellas are thought to be inherited, it is more likely for a dog to have luxating patellas if their parents did.
The OFA maintains a database of dogs that have been certified with regards to patellar luxation. Only buy puppies from people who have appropriately tested their breeding stock for genetic diseases.