Patella Luxation in Dogs

Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS

- Overview
- Diagnosis
- Treatment
- Risks
- Outlook

What is Patella Luxation?

Patella luxation describes the ability for the kneecap (patella) to dislocate out of the groove it normally sits in. This condition occurs due to abnormalities in development of the bones and joints. It usually affects both legs and is particularly common in small breed dogs. Over time the abnormal forces repeatedly pull on the patella, the soft tissues loosen, and it begins to dislocate easily.

When the patella pops out of position it is uncomfortable. The classic presentation is a dog who holds the back leg up and hops for a few steps (when the patella is luxated) before putting the leg to the floor and carrying on as normal (when the patella slips back into place). Over time, as soft tissue support weakens, this becomes less uncomfortable, but luxation happens more often. Eventually the constant wear of the femur and patella rubbing on each other causes arthritis. The joint is also much less stable than it should be, making it vulnerable to other problems such as ligament damage.

What tests are used to diagnose Patella Luxation in dogs?

Patella luxation can usually be felt on examination with the dog awake. Occasionally other problems, such as ligament damage, are also present and can only be felt under anaesthesia. Radiographs (x-rays) of the knees and hips are recommended to assess the shape of the bones and look for concurrent abnormalities such as hip dysplasia.

Surgery is the only way to resolve persistent patella luxation. It may be performed in-house, or referral to a specialist surgeon or vet with a strong interest in orthopaedics may be advised. This is more likely in very small or very large dogs, or those with other problems.

How is Patella Luxation treated?

Your dog will be anaesthetised for the duration of the procedure. The entire leg will be shaved and made sterile. The surgical incision is situated on the inner or outer aspect of the knee joint and varies in size depending on the size of the dog.

Surgery involves two techniques. First, the groove in the femur that the patella sits in is deepened, called a tracheoplasty. Secondly, the bony protuberance on the front of the tibia (called the tibial crest) is moved, as this is where the patella tendon attaches. Commonly the tibial crest has developed too far towards the inside aspect of the leg, pulling the patella off to one side. The tibial crest is detached and moved sideways until alignment is corrected, before being fixed in place using metal pins. The joint is flushed and closed, and a post-op x-ray is taken to confirm the implants are placed correctly.

What are the risks of Patella Luxation surgery?

As with any major surgery complications can occur, though these are rarely serious. The following complications can occur after patella surgery:

Infection

Superficial infections around the wound are easily treated and can usually be prevented by keeping the buster collar on your pet. Deep infections involving the joint are very uncommon but can be serious and may require removal of any implants.

Implant Loosening

The implants used to hold the tibial crest in place are not needed once healing is complete; in some cases, the body will start to push them out causing mild discomfort. Implants can be easily removed during a minor surgical procedure if needed.

Under- or Over-Correction

An uncommon complication of patella surgery is to under correct, so the patella still dislocates, or over-correct, so it dislocates in the other direction. This is most likely in very small patients, or if the deformities are very great.

Osteoarthritis

Joint instability leads to inflammation in the joint, which after time will cause arthritis. This is more common in older dogs, and those who have been lame for a long time prior to surgery. Arthritis never goes away but can be managed successfully with medication.

What is the outlook for dogs with Patella Luxation?

In general, the long-term prognosis after surgery for patella luxation is very good. Many dogs will require the same surgery in both hind limbs. This is because the deformities which cause the patella to dislocate can be bilateral (affecting both back legs). For dogs who need both legs correcting at the time of diagnosis it is advised to wait at least 6 weeks between surgeries to allow adequate recovery.

The typical time for a complete recovery from patella surgery is 8-12 weeks, though this may vary for individuals. Usually, the first 2-4 weeks will be spent with minimal or no exercise, followed by a gradual increase in controlled lead walks. Some dogs will recover very quickly while others take time and suffer more muscle loss or are unwilling to trust the leg. This varies greatly with the age and size of the dog, how acute the injury was, and how quickly surgery was performed. Some animals will benefit from physiotherapy or hydrotherapy in the recovery period; your vet will discuss this with you.

Disclaimer

Please note that the content made available on this webpage is for general information purposes only. Whilst we try to ensure that at the time of writing all material is up to date and reflects industry standards, we make no representation, warranties or guarantees that the information made available is up to date, accurate or complete. Any reliance placed by yourselves is done so at your own risk.

Page last reviewed: 16th January 2024
Next review due: 16th January 2026