Patellar luxation is when the kneecap moves from its normal position. The patella (knee cap) is in a cartilaginous groove at the end of the femur at the stifle. In dogs, the patella is an almond shape, and its purpose is to assist in the extension of the knee. 

The patella resides in the tendon of the quadriceps muscle group, which attaches to the bone (tibia) below the femur. If this muscle group contracts, it pulls on the tendon and the kneecap, thereby extending the stifle. If the patella is moved out of its groove with knee extension, it’s called a luxating patellar.

A luxating patella in a dog can lead to a ruptured cranial cruciate ligament. The literature states that at least 15% to 20% of dogs with patellar luxation will eventually rupture their cranial cruciate ligament. Two main reasons why this scenario may follow are:

A luxating patellar will change the biomechanics of the knee and subject the cranial cruciate ligament to more stress and strain, and

If the luxating patellar is chronic with arthritic changes, the inflamed environment inside the joint will cause a breakdown of the ligaments (especially cruciate ligaments).

What are the early signs and symptoms of a luxating patella?

Symptoms of luxating patella in dogs can vary, depending on the severity of the condition, however some common symptoms are:

• Limping
• A skip in the gait
• Loss of support on the limb
• Abnormal posture with the knee placed outwards
• A ‘skipping’ or ‘hopping’ lameness where one or both legs are held up for several steps while running, then return to normal
• Pain or discomfort, especially when the patella is out of place
• Swelling or thickening around the knee joint

Sometimes, acute cases can lead to erosion of the cartilage on the femur from the constant friction and, eventually, osteoarthritis. In this case, pain is usually involved and the lameness is more constant and severe.

What should I do if I notice my dog has patellar luxation?

Your vet will be able to give you a confirmed diagnosis and let you know the grading of severity.

A luxating patellar is usually diagnosed by feel and is assigned a grade (see below) based on the severity of the condition. 

Grade 1 is the least severe and the knee cap easily slips back into place on its own, whereas Grade 4 means the knee cap is actually stuck and fixed outside its normal resting position in the groove of the femur. An x-ray of the stifles can be performed to see if there is osteoarthritis present or any sign of cranial cruciate ligament damage.

Surgery is not always necessary for this condition. Many small dogs live their entire life with luxating patellar and it never results in arthritis or discomfort, nor does it interfere with the dog’s life. 

Grade 3 or 4 luxations normally require surgery as greater pain or discomfort will be involved, along with loss of mobility of the leg or associated injury such as a cranial cruciate ligament rupture.

What happens next?

If you think your dog has got patellar luxation, book an appointment with your vet to get a confirmed diagnosis. Until your appointment, limit your dog’s activity as much as possible.

Your vet will then do a physical examination to reach a diagnosis of patellar luxation. A grade will be assigned. Sometimes x-rays may be required to check on orthopaedic abnormalities that may be contributing. CT scans or an MRI may also be recommended.

Can I do anything to prevent my dog from developing patellar luxation?

The causes of this condition can be congenital, genetic and/or traumatic. Apart from breeding, if a dog has poor conformation, such as weak hocks, this can also cause a luxating patellar.

In these cases, even with preventative measures in place, the condition may not be preventable and still occur. 

If you suspect any joint issues or notice signs of lameness, consult with your veterinarian promptly for a thorough examination and appropriate guidance. The earlier the condition is addressed, the better the chance of treating it successfully or preventing further decline.

Otherwise, these are the steps you can take to reduce the risk of patellar luxation developing:

1. Maintaining a healthy weight for your dog is crucial for joint health. Excess weight can put strain on the joints, increasing the likelihood of orthopedic issues, including patellar luxation

2. Regular exercise - regular, moderate exercise helps maintain muscle tone and joint flexibility. Activities like walking and controlled play are beneficial. Avoid excessive, high-impact exercises that may contribute to joint stress.

3. Balanced nutrition - a balanced and well-balanced diet supports your dog’s overall health. High-quality nutrition is essential for developing and maintaining strong bones and joints.

4. Genetic considerations - if you’re considering getting a dog, especially if it’s a pre-disposed breed, choose a reputable breeder who screens for hereditary conditions.

5. Regular Vet Checkups can help identify any signs of joint abnormalities or patellar luxation early on. Early detection may allow for proactive management or intervention to prevent the condition from worsening.

6. Joint supplements - Joint supplements such as chondroitin and glucosamine may support joint health and be beneficial for dogs prone to orthopedic issues.

7. Environmental modifications - modifications at home can reduce the risk of injury. EG ramps for elevated surfaces mean less jumping so less force on the joints.

8. Physical therapy - physical therapy exercises prescribed by a vet or physio can help strengthen the muscles around the knee joint, providing additional support

What breeds and ages commonly suffer from patellar luxation?

Breeds with a predisposition for luxating patellas are Yorkshire Terriers, Pomeranians, Pekingese, Miniature and Toy Poodles, Maltese, Jack Russell Terriers, Chihuahuas, Cavalier King Charles Spaniels, Papillons and Boston Terriers.

Medium-breed dogs are less commonly affected by luxating patellas. Breeds such as Labrador Retrievers, boxers and bulldogs may experience luxating patellas later in life. 

Large breed dogs are prone to this condition. They include Labrador Retrievers, Golden Retrievers, Akitas, Malamutes, Boxers, Huskies and St. Bernards.  In the giant breeds, it may occur in adulthood due to the significant size and weight of the dog.

Genetics play a crucial and significant role in the development of patellar luxation. If a dog has a family history of the condition, it may be more likely to occur at a younger age. 

While not common, trauma or injury to the knee can cause patellar luxation. In these cases, dislocation might occur suddenly. This can happen at any age.

Treatment options: how can I help my dog?

Treatment for patella luxation is usually dependant on the severity of the patella’s condition. If you suspect that your dog has a luxating patella, it's important to have them seen by a vet who can assess the severity of the condition.

There’s a grading system for patellar luxation, where it’s graded 1-4 depending on severity.

Grade 1: The knee cap can be manipulated manually out of position but doesn’t occur spontaneously and causes no clinical symptoms. It’s usually an incidental finding. Grade 1 luxating patellas should be left and monitored, as they rarely cause any problems. However measures such as weight loss, restricted exercise or physiotherapy will help. Equally applying a brace can also greatly help to support the joint.

Grade 2: The knee cap spontaneously luxates out of position, is typically associated with a skipping lameness when the knee cap moves. With Grade 2 luxating patellas, surgery can be considered but is dependent on factors such as pain and frequency of the signs. Over time, Grade 2 medial luxating patellas can deteriorate into higher grades.

Grade 3: The knee cap is out of position most of the time, can be manipulated back into place but will luxate again quickly.

Grade 4: The knee cap is permanently out of position and can’t be manipulated back into the trochlear groove at all.

For Grades 3 and 4: Patellar luxation surgery in dogsis nearly always the recommended treatment. These gradings mean cartilage erodes and causes the development of osteoarthritis over time. Similarly, dogs who have medial luxating patellas are more prone to developing cruciate ligament disease. As with most things, the earlier a problem is addressed, the better it is for the dog in both the short and the long term.

There are a variety of surgical techniques which can be used. The choice depends on the individual case and the individual vet’s expertise. Usually, it is one or more of the following:

• Deepening the trochlear groove. 
• Transposition of the tibial crest to a more lateralised position (moving it sideways to straighten up the patella mechanism) - this is held in place with one or two small pins and a piece of wire to hold the tension.
• Release of medial tissue - cutting / loosening tissues on the inside of the leg to reduce sideways tension on the patella and patella tendon.
• In some extreme cases, surgery to correct the bowing of the femur may be required.

Post-surgery, your dog will probably have to wear a soft bandage or brace for 3-5 days. This is to protect the area that’s been operated on. Exercise will be restricted for 4-8 weeks after surgery. You should keep your dog on a short lead for toilet breaks. 

Your dog might need to be crated or kept in a small space, to restrict activity and movement so that healing can progress. 

Physiotherapy and hydrotherapy can both help post-surgery. They help maintain muscle mass and your dog return to normal function as quickly as possible.

How to help around the house

As mentioned above, ramps to elevated spaces such as beds or getting into cars can help prevent excessive force on the knee cap and knee joints.

Non-slip dog socks can help minimise twisting or rotation, and subsequent luxation of the kneecap.

This neoprene knee brace offers lightweight support to the muscles and ligaments of the knee joint and can be worn for extended periods of time (but should be removed if your dog is left unattended or resting/sleeping)

Conclusion

The prognosis for dogs with a luxating patella can vary depending on the severity of the condition and the chosen treatment approach. In many cases, with appropriate management or surgical intervention, dogs can experience significant improvement in their quality of life.

It’s worth noting that luxating patella can often be a progressive condition. Dogs with a history of luxating patella can be more prone to developing arthritis in the affected joint later in life. 

Regular monitoring and proactive management, such as giving a joint supplement or applying a brace to support the joint, can help minimise long-term complications.