Luxating Patellas in Dogs

Luxating patellas present in two different forms. The initial presentation is more common in young dogs which present with a non-painful and intermittent skipping gait on the affected leg. Older dogs present once osteoarthritis has developed resulting in joint pain and reluctance to walk, jump, or climb.

Patellar luxation varies in severity, which is graded from 1 to 4:

Grade 1: Luxates with manual pressure but returns to the normal location. The patella does not luxate during everyday activities and symptoms are not normally seen.

Grade 2: Luxates during everyday activity but readily returns to the normal location. May be symptomatic or asymptomatic.

Grade 3: The patella is luxated permanently but can be moved back into the normal location.

Grade 4: The patella is luxated permanently and cannot be moved back into the normal location.

Luxating patella is a common presentation in small-breed dogs, although it is sometimes seen in larger dogs. Yorkshire Terriers, Pomeranians, and Toy Poodles are particularly overrepresented in reported cases.

LP is not usually a painful condition initially, and symptoms develop as a result of mechanical instability when the patella luxates. Over time, the patellar luxation triggers osteoarthritis, which results in pain and limited mobility. Cases of possible LP require veterinary attention, but are not an emergency.

Long-standing LP predisposes to cranial cruciate ligament rupture, which can be very painful and requires additional management, including surgery.

Luxating patella is normally a developmental condition resulting from bone deformities of the shin bone and femur (thigh bone). These deformities are more common in small dogs. The deformity leads to poor alignment of the thigh muscles running down the front of the leg. The normal patella runs in a groove on the femur which forms as the puppy grows. Dogs with LPs sometimes do not form the groove correctly, which exacerbates the condition.

Rarely, LPs occur as a result of injury to the knee.

Rear leg lameness is often intermittent and non-painful. In addition, dogs with luxating patellas may exhibit characteristic skipping or hopping, intermittent inability to straighten a rear leg, bunny hopping, and pain on palpation of the knee.

Diagnosis of luxating patella involves:

• Physical examination
• Diagnostic imaging, including X-rays and CT scan

Treatment options depend on severity. Conservative management is appropriate for Grade 1 and asymptomatic Grade 2 patellar luxation. Conservative treatment involves:

• Weight management
• Exercise management
• Pain relief
• Anti-inflammatories
• Nutraceuticals

Symptomatic Grade 2 luxation, as well as Grades 3 and 4, often require surgical correction.

Prognosis varies depending on the grade of patellar luxation. Low-grade, asymptomatic cases may never require treatment or develop secondary arthritic changes. High-grade luxations that present with significant lameness usually require extensive surgical management and are likely to need treatment for osteoarthritis in the future. Prognosis following surgery is normally good but some cases may recur.

Patellar luxation may have an inherited component. Dogs with LPs should not be bred.

While prevention of LPs in an individual is not possible, the impact of the condition can be reduced with appropriate weight control, exercise management, and nutraceuticals.

LP is a common presentation, particularly in small-breed dogs under 10 kg.

• Weight management
• Exercise management
• Pain relief
• Anti Inflammatories
• Joint supplements
• Surgery