Patellar Luxation in Dogs

If your dog’s patellar luxation is congenital (present at birth), the affliction may not be noticed until about six weeks of age because it can be mistaken for clumsiness or slow learning. Developmental luxation is usually thought to be from hereditary ligament or skeletal conformation and will be evident as your puppy ages. Any kind of injury to the leg such as a fracture or sprain, can cause immediate patellar luxation that is obvious right away.

The most commonly affected breeds of dog include the Shih Tzu, Toy Poodle, Chihuahua, Maltese, Pomeranian, Yorkshire Terrier, Japanese Chin, Beagle, Pekingese, Basset Hound, Chow Chow, Cocker Spaniel, Australian Shepherd, Chinese Shar Pei, Lhasa Apso, Shiba Inu, and Dachshund. Some large breeds that are affected include St. Bernards, Huskies, Boxers, Malamutes, Akitas, Golden Retrievers, and Labrador Retrievers.

A patellar luxation is a common disorder in which the kneecap is displaced or dislocated from the knee joint where it belongs. This may be a condition the dog has when born (congenital) or may develop later in life (developmental). Although trauma to the knee can cause patellar luxation, it is usually hereditary in nature and affects toy breeds most often.

However, other breeds have been reported as having patellar luxation as well. This condition causes mild to severe pain, depending on which grade of luxation your dog has. Unless it is caused by an injury, the grade starts at 1 (mild) and progresses to 4 (severe) without treatment. If it is caused by an injury, it can start at any grade, depending on the severity of the injury. Patellar luxation is almost always in the rear legs and will cause lameness eventually without treatment, causing a skipping type gait.

The symptoms of patellar luxation depend on the cause and the grade of the condition. Most commonly, the signs include:

• Limping
• Abnormally carrying leg or legs
• Inability to bend the knee
• Pain when moving the leg
• Will not run or jump
• Refusing to exercise
• Swelling
• Weak legs
• Crying out in pain when used or manipulated

Types

A patellar luxation comes in four different grades depending on severity. These grades include:

• Grade 1 – Minimal lateral deviation, no cracking sounds, slight rotation of the tibia, and returns to the original position after extension
• Grade 2 – Up to 30 degrees of torsion in the tibial crest, frequently moves from its intended position, almost permanently luxated, very difficult but possible to move patella back in place
• Grade 3 – Flattened knee joint, permanently luxated with a tibial crest of 30 to 50 degrees, still usable but held in a partially flexed position
• Grade 4 – Permanently luxated with up to 90 degrees deviation, knee joint is flat or convex, unable to use the leg normally

The cause of patellar luxation includes:

• Congenital – Present at birth
• Developmental – Develops over time but is considered to be a hereditary deformity or weakness in the ligaments or bones in the knee
• Traumatic – Results from an injury or accident that damages the knee ligaments or bones

If this is a congenital condition, your puppy will probably be diagnosed at his first appointment with your veterinary professional. However, in the case of hereditary or traumatic patellar luxation, the condition will make itself known when it is at a high enough grade. A physical examination will be performed right away, which will likely include auscultation, palpation, vital signs, lameness assessment, and behavioral analysis. 

Be sure to tell the veterinarian if your pet has been sick or injured recently and if you have given him any medication, even if it is an herbal supplement. Some medications can affect the symptoms and may not interact well with the drug your veterinarian proposes to use for treatment. The veterinarian will run some blood tests such as a blood count and chemical analysis as well as radiography like x-rays, CT scans, ultrasound, and an MRI.

To treat your dog for patellar luxation, the grade and your dog’s health will be taken into consideration. Surgery is the most obvious and commonly chosen treatment, but the veterinarian may try a leg brace or bandage, cage rest, and medication instead.

Surgery

The operational technique depends on the grade of the condition and the results vary depending on the cause of the patellar luxation. The veterinarian may choose to use fascial release incisions on the side of the knee or knees affected, soft tissue realignment, inserting pins into the tibia to create a fixed position, or bone shaping to deepen the groove of the femur.

Medication

Steroids, NSAIDs, and narcotics can be given for pain and inflammation. In addition, there are supplements such as glucosamine, Vitamin C, Vitamin E, and collagen injections that may be helpful for pain.

Your dog’s prognosis is good but depends on the grade of the patellar luxation. In very severe cases, the limb may need to be amputated to stop the pain. Mild to moderate cases are treated with surgery or medication and should return your dog to normal health in no time at all.