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Patellar Luxation in Dogs

Pumpkin’s Story and Patellar Luxation in Dogs

“Pumpkin” was a beautiful two-year-old Pomeranian dog. She had been brought into the surgery recently, as over the past year it had been noted that she was occasionally lame on one or both of her hindlegs. Pumpkin was not particularly bothered by her lameness, and she was always bright and happy, prancing along gaily on her favourite walks. Her owner was noticing the lameness more often now though, and she was occasionally seen hopping now on either back leg. 

On her previous examinations when she was younger it had been noted that she had mild luxating patellae in both hindlimbs. On this examination it was noted that this was progressing into a more regular lameness, and her grade of noted luxation had increased. So, it was advised that she now have surgeries to correct this. 

Patellar luxation is a displacement of the patella, the “kneecap,” to the side of the knee joint. It can be a cause of a hindlimb lameness, and occasionally pain.  

The patella is the kneecap which is essentially a small piece of bone that covers and protects the front of the stifle joint, the knee joint, on the back legs. In the thigh bone (the femur) there is a groove (the trochlea) in which the patella slides, and there are ligaments which hold the patella in place. Patellar luxation happens when there is a displacement of the patella to the side of the knee joint.  

This condition often occurs if the groove (the trochlea) is too shallow, and when the dog bends the knee, the patella pops out of place. The patella can dislocate out of this groove, and this luxation therefore prevents the knee from bending and extending properly. Other conformational issues, such as a displaced patellar tendon and bowed hindlimbs, can also add to the predilection of certain breeds to have this problem. 

Luxating patella is most often a congenital disease that is due to an abnormal alignment of the bones and joints of the hind leg. It is rarely acquired through any trauma. It can affect any dog breed but more commonly affects the toy and miniature breeds, such as Poodles, Pugs, Chihuahuas, Yorkshire Terriers and Pomeranians. The condition will sometimes only affect one leg but can be seen in both knees in around 50% of dogs. 

Some puppies may show signs of the problem early on. Other dogs show symptoms later in life. Initially while the condition is mild, the patella may be in place most of the time and may pop out of place occasionally. 

The dog may have a gait which is normal most of the time but, when the patella slips out, the gait can become abnormal. There may be a lameness and the foot may turn inward when the patella is out of place. Patellar luxation is usually characterised by an intermittent, ‘skipping’ or ‘hopping’ lameness, where the dog will hold their affected leg up for several steps whilst exercising, and then return to normal as the patella pops back in on its own, and then the dog usually walks normally again. When both legs are affected, you may see ‘bunny hopping’, as well as a stiff and awkward gait. In the early stages of luxating patella, the condition may not cause too much discomfort to the dog but can occasionally lead to a more painful osteoarthritis over time as cartilages within the joint are eroded by this abnormal movement. 

Diagnosis of luxating patella is made by a physical examination of the stifle joint. During the examination, your vet will be able to manipulate the patella out of place to confirm the diagnosis. In some cases, X-rays may be required to fully assess the knee joint and surrounding conformation. 

Depending on the ease of dislocating the patella and whether the patella returns to the groove spontaneously, the degree of luxation is graded from one to four. 

Treatment of Luxating Patella is usually dependant on the severity of the patella’s condition. Grade 1 luxating patella can often be left and monitored, as they rarely cause any problems. With grade 2, surgery can be considered, and this is dependent on the frequency of the signs as over time grade 2 cases can deteriorate into higher grades. Surgery is the recommended treatment for grades 3 and 4, as this level can eventually cause the development of osteoarthritis over time. 

Surgical repair involves correction of some, or all, the following: To make the trochlea groove deeper; To release ligaments in the direction of the luxation; To tighten ligaments opposite the direction of luxation; or to reposition the attachment of the patellar ligament below the knee.  

The total recovery time after surgery is normally about eight to ten weeks, with strict rest advised, and post operative physiotherapy and hydrotherapy can also greatly assist recovery.  

The outlook after correction of patellar luxation is generally good to excellent, except for some very severe high-grade cases with concurrent osteoarthritic changes.  

Thankfully wee, bouncy “Pumpkin” recovered extremely well from her corrective surgeries on both her knees, which were done a few months apart, along with advised post operative physiotherapy, to allow a full recovery in both limbs.  

"Pumpkin" was soon prancing along on her usual walks again, making friends with everybody. 

If your pet is showing any symptoms of patella luxation, do get in touch with your Vet for an initial examination and advice. 

Alison Laurie-Chalmers

Senior Consultant
Crown Vets

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