Luxating Patellas in Dogs

Key Takeaways

Luxating patellas (LP) is a term for dislocation (luxation) of the kneecaps (patellas). LP is a moderately common condition and is seen most commonly in small breed dogs.

• Dogs with LP classically present with an intermittent hopping or skipping gait which occurs when the kneecap dislocates during movement and the dog hops on one leg until the kneecap moves back to the normal location

• Cases that are not treated in young dogs sometimes result in arthritis later in life

• Investigation of LPs involves physical examination and diagnostic imaging including x rays or CT scan

• Low grade LPs are managed conservatively with antiinflammatories, joint supplements, and weight control

• Higher grade luxations require surgical stabilization of the kneecap

• Prognosis is good following appropriate treatment

• Some cases recur and many cases go on to develop osteoarthritis

A Closer Look: What are 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 pain, reluctance to walk, jump or climb.

Patella luxation varies in severity which is graded between 1-4:

Luxates with manual pressure but returns to the normal location. The patella does not luxate during everyday activities and symptoms are not normally seen.
Luxates during everyday activity but readily returns to the normal location. May be symptomatic or asymptomatic
The patella is luxated permanently but can be moved back into the normal location
The patella is luxated permanently and cannot be moved back into the normal location

Risk Factors

Luxating patella is a common presentation in small breed dogs, although it is sometimes seen in larger dogs. Yorkshire terrier, pomeranians, and toy poodles are particularly over represented 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 patella luxation triggers osteoarthritis which results in pain and poor mobility. Cases of possible LP require veterinary attention, but are not an emergency.

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

Possible Causes

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.

Main Symptoms

Symptoms of patella luxation include:

• Rear leg lameness (often intermittent and non-painful)

• Characteristic skipping or hopping

• Intermittent inability to straighten a rear leg

• Bunny hopping (more common in bilateral conditions)

• Pain on palpation of the knee

• Reluctance to jump or climb

Testing and Diagnosis

Diagnosis of luxating patella involves:

• Physical examination

• Diagnostic imaging, including X-rays and CT scan

Steps to Recovery

Treatment options depend on severity. Conservative management is appropriate for grade 1 and asymptomatic grade 2 patella 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 patella 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.

Prevention

Patella 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.

Are Luxating Patellas Common in Dogs?

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

Typical Treatment