Lateral Patella Luxation in Dogs

Being one of the most commonly diagnosed orthopedic conditions in dogs, patella luxation accounts for 75% to 80% of orthopedic conditions seen in small animal clinics, and affects 7% of puppies, as early as 8 weeks of age. Though it primarily affects small breeds, it can affect large and giant breeds. Lateral luxation is more common in giant breeds. More often both knees are affected, but it can be unilateral. Mild cases may never have a symptom in the affected limb, while more severe cases can result in pain and loss of function. 

The patella is the kneecap, and it normally rests inside a groove within the thigh bone, or femur, inside the knee. Patella luxation is a condition where the kneecap is dislocated and moves away from the femoral groove when the knee is flexed. This dislocation can be medial or lateral, depending on which side the kneecap falls to. Lateral patella luxation refers to a dislocation away from body, while medial is a displacement closer to the body. As the kneecap dislocates more often out of the femoral groove, it erodes cartilage and exposes the bone, leading to instability, pain and arthritis.

• Genu valgum stance, also called knock-knee, a seal-like stance
• Inability to stand
• Shaking of affected leg
• Extensions of affected leg
• Pulling up of affected limb for several steps
• Bow legged appearance in puppies
• Skipping gait, intermittent or continuous
• Lameness, occasional to continuous
• Pain
• Arthritis

Types

Luxation can be medial, or when the kneecap is dislocated closer to the body, traumatic when caused by a trauma or injury, or lateral, when the kneecap is dislocated away from the body. The two recognized types of lateral patella luxation are:

Lateral patella luxation of toy and miniature breeds - This is found in toy and miniature breeds, such as Boston Terrier, Yorkshire Terrier, Chihuahuas, miniature and toy Poodles, Pomeranians, Pekinese, and Cavalier King Charles Spaniels. Symptoms are often seen around 5 to 8 years of age. 

Lateral patella luxation of large and giant breeds - This type is seen in large breeds, and has affected Akitas, Great Pyrenees, Chinese Shar peis, flat-coated Retrievers, Great Danes, St. Bernards, Irish Wolfhounds, Labradors, Malamutes, Boxers, and Huskies. Symptoms often occur in puppies near 5 to 6 months old.

This condition is a direct result of abnormalities in the structure and components of the hind limb. Causes of those abnormalities can include:

• Genetic predisposition
• Trauma or injury
• Shallow or absent femoral groove
• Abnormality in the overall alignment of the knee and leg, such as hip dysplasia
• Skeletal abnormalities
• Hormonal influences during growth

Lateral patella luxation is often found during a routine exam, and may present no symptoms. If symptoms are present, your veterinarian will start with a physical examination that includes palpation of the affected kneecap, sometimes under sedation. This can allow the veterinarian to grade the severity of the luxation, and can help to determine treatment. Additional tests can determine the severity of the luxation and any other associated conditions that may be present, and can include X-rays to evaluate the bones and look for signs of hip dysplasia, and a CT scan. Patella luxation can have symptoms that are similar to osteoarthritis and neurological conditions, and other tests may be administered to rule these out. Blood tests and a urinalysis may be taken before anesthesia is given.

Depending on the severity of the luxation and any concurrent conditions, treatment will vary. If the luxation is mild and devoid of symptoms, it only needs to be monitored and generally does not need surgical correction. If the luxation is more severe, surgery may be considered. Surgery is often more difficult in larger breed dogs, especially when other concurrent conditions are present.

Surgery attempts to modify the bony structures or soft tissues, or both, and may involve a reconstruction of soft tissues that surround the kneecap, create a deeper femoral groove to allow the kneecap to stay in its normal position, or correction of other bones, such as the tibial crest or femurs. These procedures are performed in accordance to each individual dog’s needs. Surgery is recommended for dogs with severe symptoms, or in puppies with growing bones.

Over 90% of owners have reported satisfactory results after surgery. Recovery is less favorable in larger breeds, especially when combined with other conditions. Reoccurrence of the luxation is uncommon. In the rare case, the migration or breakage of implants used to keep corrected bones in position can occur. There is also a slight risk of infection. Monitor your dog’s habits to be sure his recovery is progressing, and report any leg issues or infections to your veterinarian. Prevent this hereditary condition by not breeding affected dogs.