Does your dog ever start limping, only to find by the time you get to them the limp is suddenly gone? Is your dog a toy or miniature breed? You should know about luxating patellas.
What is a patella?
A patella is the medical term for the knee cap.
What is a luxating patella?
In a normal dog knee, the patella sits in a groove on the end of the femur. When the knee extends and flexes the patella moves up and down in that groove. A luxating patella occurs when the patella slips out of the groove. When this happens you will notice your dog is unable to bend their knee and may take a few steps without using that leg. After a few steps they will likely start to run completely normal again. Most commonly the patella slips out to the inner aspect of the knee, this is called a medial luxating patella.
Luxating patellas are graded from 1 to 4.
Grade 1: The patella sits in the groove, but can be dislocated when a veterinarian forces it. The patella pops right back into normal position. This typically does not cause any obvious symptoms.
Grade 2: The patella intermittently will pop out of the groove but the dog will be able to pop it back into place. The patella sits in the groove the majority of the time. Lameness may be intermittently noted when the patella luxates.
Grade 3: The patella sits outside the groove the majority of the time but it can be manually replaced into the correct spot. Dogs may exhibit signs of pain such as holding the leg up or limping.
Grade 4: The patella sits out of the groove all the time and it cannot be manually replaced into correct positioning. Dogs will typically show signs of pain, such as limping and not using limb. Arthritis builds very fast in these dogs.
Will luxating patellas cause any long term issues?
The higher the grade of luxating patella, the more likely there is going to be complications. Dogs with lower grade luxating patellas, typically grade 1 and 2, can live their whole lives without having major issues. With higher grade luxation, arthritis builds much faster, leading to pain and dysfunction of the joint. Luxating patellas can make injury to the ACL (known as the cranial cruciate ligament in dogs) more likely. About half of all dogs that have luxating patellas will have them in both legs.
Can a luxating patella be fixed?
Yes! Surgical correction of the luxating patella is possible. Only grade 2-4 are repaired. The type of surgery chosen will depend on the confirmation of the dog. Most commonly the groove that the patella sits in is deepened so it no longer is able to pop out of place. Other surgical options include moving the area of the bone where the patellar ligament attaches to the tibia or tightening the joint capsule around the knee.
Prognosis
The overall prognosis of a luxating patella is determined by the amount of arthritis that has built at the time of surgery. The early the surgery is performed the better outcome. A young dog that has surgery done soon after diagnosis has an excellent prognosis.
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