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A luxating patella, in which a kneecap moves out of its normal position, is a very common occurrence in dogs. While small or toy breeds, such as Chihuahuas, Yorkshire terriers and Pomeranians, are the most prone to a luxated patella, this orthopedic condition can affect all breeds of dogs.
Sometimes a luxating patella can be treated with physical therapy and medication. However, surgery may be necessary if your dog's condition is severe and causes them significant pain.
How Does A Luxating Patella in Dogs Occur?
A luxating patella occurs when the dog patella (kneecap), which normally sits on the groove of the femur (thighbone), shifts out of alignment. It can occur in one, or both, of the hind legs. In most small breed dogs, this movement occurs medially or toward the inside of the limb. A luxating patella in dogs can happen laterally, but this is less common and usually only occurs in larger breeds.
When luxation of the patella occurs, your dog may experience intermittent hind limb "skipping," lameness, or a locking up of the limb at an odd angle. Once everything realigns, they return to normal as if nothing had happened.
A luxating patella in dogs can stem from a traumatic injury but more commonly is associated with joint or limb structure abnormalities, such as the groove of the femur where the kneecap sits being too shallow, or the area where the kneecap attaches to the shinbone (tibia) being displaced. These limb and joint changes result in an alteration of forces placed on the knee and, in turn, luxation of the patella.
How Is A Luxating Patella in Dogs Diagnosed and Graded?
A luxating patella in dogs is diagnosed by a veterinarian through a physical examination and is graded based on severity (I-IV). When assigning a grade, the vet will take into account any signs of discomfort that you've seen in your pet.
- Grade I: The kneecap dislocates out of its normal position with manual pressure but returns immediately when it's released. Grade I is usually found incidentally on examination by a vet and usually doesn't result in clinical symptoms.
- Grade II: The kneecap readily shifts out of its normal position with manual pressure and remains displaced until it's manually adjusted. Lameness is usually intermittent when the patella luxates out of its normal position and can be painful if there's damage to the cartilage caused by frequent luxation.
- Grade III: The kneecap is disjointed most of the time but can be returned to its normal position with manual pressure; however, once this pressure is removed, the patella begins to spontaneously luxate. Due to limb structure changes and/or cartilage damage from repeated luxation, dogs at this grade may experience more pain and exhibit more lameness.
- Grade IV: The kneecap is permanently dislodged from its normal position and cannot be manually replaced. Severe limb structure changes are usually present, which can lead to lameness and otherwise impaired mobility, and reduced limb function.
Some dogs with a luxating patella may also have concurrent rupture of their cranial cruciate ligament — the human equivalent of an ACL.
How Is Luxating Patella Treated?
The methods for treating a luxating patella in dogs range from conservative medical management to surgery, depending on the grade of the disease.
Most grade I and grade II instances are treated through pain and anti-inflammatory medications, weight management and exercise restriction. Physical rehabilitation therapy may also be helpful here, as it can help your dog rebuild muscle strength and ease back into normal activities. Some dogs with grade II who experience significant pain from cartilage damage and significant lameness may benefit from surgery to improve their quality of life. Surgery is usually indicated for both grade III and grade IV patellar luxation as they can cause significant lameness and pain.
Surgeries for dog patella luxation are divided into those that correct either bony or soft tissue structures. No matter the surgery, the overall goal is to realign the supporting structures of the knee joint to allow the kneecap to move normally and stay in the groove of the femur. Common surgical procedures include:
- Techniques to deepen the groove on the femur where the kneecap sits.
- Moving the joint that attaches the kneecap to the shinbone more laterally.
- Reinforcing the knee joint's soft tissue structures.
Surgery is often staged if both of the dog's hind limbs are affected, starting with operation on the most affected knee first.
To allow the site to heal appropriately, your dog may have to wear a soft bandage or brace for three to five days and have their exercise restricted for about four to eight weeks following surgery. During this recuperation time, your dog's walks should be limited to short on-leash trips to use the bathroom, and they may have to be crated or confined to a small room to restrict activity. Physical rehabilitation can be helpful to reduce the loss of muscle mass on the affected limb and may help some dogs return to normal function sooner.
Moving Forward With Patellar Luxation
Luckily, many dogs with this disease don't even need surgery to resume their normal active life. Sometimes all it takes is a little rest, relaxation or physical therapy. But even if your dog does need to go through surgery to restore their range of motion, they probably won't be down and out for too long. As soon as a few months after their procedure, they're likely to be back to their same playful selves.
Dr. Jessica Seid
Jessica Seid is an emergency veterinarian practicing in the New England area. She is a graduate of the North Carolina State College of Veterinary Medicine and has been in the field for more than a decade. When she's not helping patients, she enjoys spending time with her husband, daughter and French bulldog.