Medial Patella Luxation in Dogs

Medial patella luxation should be considered an inherited disease, meaning that the parents or grandparents can produce the disease. While any dog can be diagnosed with medial patella luxation, small breed and toy breeds are more susceptible as most have loose patellas by one year of age. Breeds such as Boston Terrier, Yorkshire Terrier, Pomeranian, Chihuahua, Miniature Poodle and Toy Poodle have a higher incident of medial patella luxation.

Medial patella luxation in dogs is when the patella, or kneecap, shifts out of place in a medial position. Dogs can be affected by patella luxation by the time they are 8 weeks old, however, dogs of any age can become affected.

The symptoms of medial patella luxation will vary depending on the severity of the disease. Some dogs that have had luxating patellas since puppyhood may have adapted to patella popping out of place and compensate for it. When your veterinarian does a physical examination, she should detect any extra luxation within the patellas. If you do notice any of these symptoms, make an appointment with your veterinarian for a thorough physical examination.

• Carrying a leg up all the time
• Skipping or carrying the leg a few steps and setting it down
• Shaking the leg before putting weight on it
• Extending the leg before putting weight on it
• Bow-legged appearance
• The knee over-extending when standing or walking

Types

Grade 1

The patella can be moved out of place but it will move back into its natural position when let go. Many breeders and veterinarians will term a Grade 1 as loose patellas. Grade 1 does not require surgery.

Grade 2

This is when the kneecap does not move back into its natural position when let go. Grade 2 should be considered for surgery to prevent further damage and arthritis from developing. Some veterinarians will opt for rest and possible bracing before scheduling surgery.

Grade 3

The kneecap stays out of place but your veterinarian can move it back into its natural position. The kneecap will move back out of place when let go. Surgery is strongly recommended for Grade 3 luxation.

Grade 4

The kneecap stays out of place and cannot be moved back into place by hand. The dog has a hard time extending his knees and will walk with his knees bent. Surgery is strongly recommended by an orthopedic surgeon.

In most cases, medial patella luxation is a result of a genetic deformity or some form of trauma. Responsible breeders will be aware of the likelihood of luxating patellas within their bloodlines and will do their best to eradicate this issue when breeding. Trauma could be from jumping on and off furniture, climbing steps, slick flooring and accidents.

Most veterinarians can diagnose medial patella luxation by palpating the patella or kneecap. Your veterinarian will compare the weak knee with your dog’s other knees as a point of reference. This may be done under sedation so your dog is not overly stressed. Once an initial diagnosis of a luxating patella has been given, your veterinarian will order x-rays of the knee, pelvis and tibias. This will give a visual of the shape of the bones within the rear legs and definitively rule out hip dysplasia. 

Your veterinarian may also order a CT or CAT scan. This will provide a three-dimensional image of the skeletal features of both rear legs. A CT or CAT scan will allow a surgeon to see exactly where to focus when surgically correcting the medial luxating patella. Urinalysis and blood tests will be completed prior to anesthesia as a precaution to ensure that your dog does not have any underlying health issues that could cause problems during surgery.

Grade 1 medial patella luxation will not require surgery; your dog will need to be monitored so the luxation does not worsen. Grade 2 medial patella luxation may require surgery, depending on the recommendation of your veterinarian.

Grade 3 and Grade 4 medial patella luxation will require surgery. Most veterinarians will refer you to an orthopedic specialist for the surgery. Your surgeon will walk you through the procedure and the expected outcome.

Your veterinarian will establish the best treatment plan for your dog. If surgery is required, be sure to follow all post-operation instructions and give all prescribed medications. 

Follow up visits with your veterinarian will ensure that your dog is healing properly. In the event that the patella luxation is not severe enough for surgery, your veterinarian will still want to set up follow up visits to ensure that the luxation has not become more serious.