Lateral Patella Luxation (LPL) in Dogs

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Overview of Canine Lateral Patella Luxation 

Lateral patella luxation (LPL) is a condition in which the patella, or knee-cap, no longer glides within its natural groove in the femur, the upper bone of the stifle or knee joint that can occur in dogs. It becomes displaced to the outside of the joint and can be partial or complete, intermittent or permanent. LPL can occur as a result of trauma, develop during the first year of an animal’s life in large and giant breeds of dogs or occur when they are more mature in small breeds.

Medial patella luxation (MPL) is more common in all breeds of dog than LPL. LPL is seen in large and giant breeds more frequently than small breeds of dog, such as Great Danes, St. Bernards and Irish wolfhounds. In the large and giant breeds, LPL is more common in both knees. Animals may show symptoms during the first year of life, particularly if the abnormality is severe, or any time later in their life if the problem is lower grade and leads to a more progressive, chronic lameness. Traumatic patella luxation can occur at any age and is usually secondary to being hit by a car.

Lameness can vary from an occasional hitch of the leg, like an intermittent skipping, to a persistent weight bearing lameness. Traumatic luxations are more likely to result in a non-weight bearing lameness.

Diagnosis of Lateral Patella Luxation in Dogs

  • Initial observation is important. The animal is observed walking and trotting. In a standing position, the knee joint of the affected leg is compared to the opposite side.
  • The veterinarian will put the knee joint through a normal range of motion to feel the tracking of the patella during flexion and extension of the joint. Depending on the severity of the problem, the patella may move only slightly toward the outer aspect of the joint or may pop completely and audibly out of position.
  • X-rays of the knee can be helpful to document the luxation.
  • Treatment of Lateral Patella Luxation in Dogs

  • Low grade LPL may be an incidental finding in which no treatment is necessary other than being aware of the clinical signs that may develop and closely observing your pet for development of this problem. In some cases LPL may be managed conservatively with restricted exercise and non-steroidal anti-inflammatory medication.
  • More severe grades of LPL should be addressed surgically. There are a variety of surgical options depending on which factors within and around the knee joint contribute to the luxation.
  • Home Care and Prevention

    Following surgery your dog may be sent home with the leg in a soft padded bandage. This should be kept clean and dry at all times and the toes at the bottom of the bandage checked twice daily for swelling and/or pain. For many large and giant breeds of dog, keeping a bandage in place following surgery can be difficult and therefore may not be deemed worthwhile.

    Most animals will require exercise restriction for the first four to six weeks following surgery. The bandage and stitches are removed at 10 to 14 days. Passive flexion and extension of the knee can be helpful to reduce joint stiffness and this will be demonstrated by your veterinarian if appropriate.

    Congenital LPL is commonly a bilateral problem, that is it affects both hind legs, though not necessarily to the same degree. When selecting a dog, ask the breeder about the history of patella problems in the bloodline.

    Be on the lookout for your dog developing a knock-kneed stance that may be indicative of LPL during the growing months of life.

    Since trauma can occasionally lead to development of LPL, your dog should remain on a leash when walking and have a properly fenced in yard at home.

    In-depth Information on Lateral Patella Luxation in Dogs

    Related Symptoms or Diseases

    There are many other causes of lameness referable to the knee joint. These diseases would be considered during the history taking and the physical examination. Some examples would include the following:

  • Medial patella luxation. The same clinical signs as lateral patella luxation are present, but the displacement is to the inside rather than the outside of the knee. This disorder occurs more frequently in smaller breeds of dog.
  • Cranial cruciate ligament rupture. Like patella luxation this injury can result from an acute traumatic event or develop as a chronic lower grade lameness. It is not uncommon to have combinations of patella luxation and a torn cranial cruciate ligament.
  • Collateral ligament injury. The collateral ligaments are located on the inner (medial) aspect and outer (lateral) aspect of the knee joint. They are most commonly injured in major trauma to the whole joint called stifle luxation or a deranged stifle. The medial collateral ligament and the cranial cruciate ligament are often both torn together with damage to the cartilage shock absorber, the meniscus, that lies between the two major bones of the knee joint. The patella is not normally affected in this injury.
  • Patella fractures are uncommon and would present as an acute traumatic lameness, usually as a result of a direct blow.
  • Patella tendon rupture is even less common and results in the patella being displaced above the knee joint, not out to one side or the other.
  • In young dogs, the position of the knee-cap may be altered due to a fracture at the attachment of the patella ligament to the bone below the knee joint, the tibia. This fracture is called an avulsion of the tibial tuberosity and requires surgery to return the fragment, the tendon and the knee-cap to their appropriate positions.
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