Luxating patella is movement of the patella, aka knee cap, outside of the groove it should sit in at the front of the knee.
Normally the patella should sit in the groove of the femur (ie thigh bone), but when it moves outside of the groove it can cause pain and abnormal movements for our dogs. Patellar luxation is one of the most common orthopedic conditions in dogs. This condition affects mostly small dogs such as Boston and Yorkshire terriers, Chihuahuas, Pomeranians, and miniature poodles. Larger breeds are less likely to have patellar luxation but it doesn’t make them immune.
What Causes Patellar Luxation?
- Trauma (e.g. fall from height, jump, hit by car)
- Abnormal alignment of the hip joint (such as in hip dysplasia)
- Malformed, poorly angled or rotated bones in the back legs
- Quad muscle tightness
- Patella tendon that is too long
- Poor positioned attachment of the patellar tendon on the shin bone
- When their is a congenital (ie. genetic cause), luxation usually occurs on both sides
What are the Signs and Symptoms of Patellar Luxation?
- Skipping for a few steps and/or shaking or kicking a leg backwards
- The dog is trying to put the patella back into place
- Hind leg lameness
- Bowed legs in small dogs and puppies
- Knock kneed in large animals
I think my dog has luxating patella…now what?
Your dog should be assessed by your veterinarian. They will have a look at the way your dog moves and do some hands-on testing of the patella as well as x-rays to look for bony issues. They will then give your dog a grading if the patella is moving out of the groove:
- Grade I – the patella can be manually moved out of place but will replace itself without assistance
- Grade II – the patella moves out of place occasionally and will replace itself with manipulation (ie. kicking the leg)
- Grade III – the patella moves out of place most of the time and can be replaced with manipulation
- Grade IV – the patella is always out of place and it cannot be moved back into place
Click here to see this visually.
What are the treatment options for patellar luxation?
Grade I and grade II patellar luxations can be managed conservatively without surgery. Lifestyle changes should be made to monitor activity levels and to maintain a healthy weight as well as adding joint supplements and rehabilitation. Canine rehab will focus on strengthening of specific muscles to help the patella track better in the groove and lengthen any tight muscles that could be contributing to the patella moving out of the groove. Modalities such as laser and acupuncture can help with pain relief.
Grade III and IV subluxations likely require surgery. Surgery may involve moving the attachment of the patellar tendon, deepening the groove for the patella, tightening the joint capsule (ie. the sack around the joint) to keep the patella from luxation or releasing tight muscles. A surgeon would determine which type of surgery is most suited to your dog.
It is important to remember that although the surgeon has repaired the defect in the knee causing subluxation, it cannot strengthen the muscles around the dog’s hip and knee. We wrote a previous blog about why your dog needs rehab after surgery if you want to learn more. As well, rehab is important after surgery for luxating patella as reluxation can occur.
Even if your dog doesn’t seemed bothered by their luxating patella it is important to seek treatment. Many dogs can function well for a long time with a luxating patella but overtime it places abnormal stress on the knee and leg. This can lead to arthritis as well as a 15-20% increased risk of CCL tear over time.