Patellar Luxation in Dogs: Understanding, Managing, and Preventing a Common Orthopaedic Condition

Patellar luxation is one of the most common orthopaedic conditions affecting dogs, particularly small and toy breeds. It occurs when the kneecap (patella) slips out of its normal position in the groove of the thigh bone (femur). The condition can range from a mild, occasional problem to a severe, painful disorder that affects mobility and quality of life. Understanding its causes, symptoms, diagnosis, and treatment options is essential for ensuring your dog’s comfort and long-term wellbeing.

What Is Patellar Luxation?

The patella is a small, flat bone that sits in front of the knee joint and slides within a groove at the end of the femur as the leg bends and straightens. It acts as a fulcrum for the quadriceps muscles, helping to extend the leg. When the patella moves out of its normal alignment, usually to the inside (medial) or, less commonly, to the outside (lateral) of the knee, this is called patellar luxation.

When the patella dislocates, the joint cannot function properly, leading to pain, lameness, and in chronic cases, arthritis and deformity of the limb.

Types of Patellar Luxation

There are two main types, based on the direction the kneecap moves when it dislocates:

• Medial patellar luxation (MPL): The patella slips inward, toward the inside of the leg. This is the most common type and is especially prevalent in small and toy breeds such as Chihuahuas, Pomeranians, Yorkshire Terriers, and Poodles.
• Lateral patellar luxation (LPL): The patella slips outward, toward the outer side of the leg. This form is more often seen in larger breeds, such as Labradors, Great Danes, and Mastiffs, though it is less common overall.

Some dogs may have both knees affected, either equally or to varying degrees.

Causes and Risk Factors

Patellar luxation can be either congenital (present from birth) or acquired later in life due to trauma or joint degeneration. The congenital form is by far the most common and is usually linked to abnormal bone or muscle development around the knee.

Common Causes

• Genetic predisposition: Inherited structural deformities such as shallow femoral grooves, malalignment of the quadriceps mechanism, or abnormal hip or tibia structure.
• Trauma: Sudden injury can displace the kneecap and damage ligaments, particularly in active or working dogs.
• Poor limb alignment: Abnormal bone growth or muscle imbalance during development.
• Degenerative joint disease: Arthritis or wear on joint tissues can destabilise the patella.

Risk Factors

• Small or toy breeds
• Rapid growth in puppies
• Overweight or obese dogs
• High-impact activity or jumping on hard surfaces
• Hereditary predisposition (especially if parents were affected)

Symptoms and Signs

The symptoms of patellar luxation depend on its severity. In mild cases, the problem may be intermittent or even unnoticed, while severe luxation can cause persistent pain and abnormal gait.

Common signs include:

• Skipping or hopping gait: The dog may occasionally lift a hind leg for a few steps, then resume walking normally.
• Intermittent lameness: The dog may show sudden bouts of limping that come and go.
• Knee “locking” or stiffness: The dog may appear to struggle to bend or straighten the leg.
• Popping sound: Occasionally, you may hear or feel the kneecap popping in and out of place.
• Pain or discomfort: The dog may whimper, lick at the knee, or resist handling.
• Arthritis and reduced mobility: In chronic cases, inflammation leads to reduced activity and stiffness, especially after rest.

Grading the Severity

Veterinarians classify patellar luxation into four grades based on how easily the patella moves out of place and whether it returns on its own:

1. Grade I: The patella can be manually dislocated but returns to its normal position immediately when released. Usually no visible lameness.
2. Grade II: The patella occasionally dislocates on its own but can be easily replaced by the dog or the vet. Intermittent lameness or skipping gait may occur.
3. Grade III: The patella is dislocated most of the time but can be manually repositioned. The dog often shows consistent lameness and discomfort.
4. Grade IV: The patella is permanently dislocated and cannot be repositioned manually. The limb is often deformed, and severe lameness or an abnormal gait is present.

Diagnosis

A veterinarian will diagnose patellar luxation through:

• Physical examination: Manipulating the knee joint to assess stability and determine the grade of luxation.
• Gait analysis: Observing how the dog walks, runs, or sits.
• X-rays: To identify bone abnormalities, arthritis, or concurrent issues such as hip dysplasia.
• Advanced imaging (CT scan): In complex or surgical cases, to assess bone alignment and plan corrective surgery.

Treatment Options

The treatment approach depends on the severity of the condition, the dog’s age, activity level, and overall health.

Non-Surgical Management

For mild cases (Grade I or mild Grade II):

• Weight control: Reducing excess body weight to relieve pressure on the joints.
• Exercise moderation: Avoiding activities that strain the knees, such as jumping from furniture.
• Physiotherapy and strengthening exercises: To build up supporting muscles around the knee.
• Joint supplements: Glucosamine, chondroitin, and omega-3 fatty acids may support joint health.
• Pain relief and anti-inflammatories: Prescribed during flare-ups.

Non-surgical management can be highly effective in mild cases but requires consistency and lifelong monitoring.

Surgical Treatment

Moderate to severe cases (Grade II to IV) usually benefit from surgical correction to restore normal patellar alignment and prevent long-term damage.

Common surgical techniques include:

• Trochlear deepening: Deepening the femoral groove to hold the patella securely in place.
• Tibial tuberosity transposition: Realigning the attachment of the patellar ligament to improve tracking.
• Soft tissue reconstruction: Tightening or releasing ligaments and tendons to stabilise the kneecap.
• Correction of bone deformities: In advanced or congenital cases, reshaping bones to restore normal limb alignment.

Post-operative care includes controlled exercise, physiotherapy, and pain management. Full recovery typically takes 6–12 weeks, depending on the procedure and individual healing rate.

Prognosis and Recovery

The prognosis for dogs with patellar luxation is generally excellent, especially when treated early and appropriately. Mild cases often lead normal lives with minimal intervention, while surgical correction boasts success rates exceeding 90% in restoring mobility and comfort.

However, dogs with chronic or severe luxation may develop arthritis over time, requiring long-term management and supportive care.

Prevention

While not all cases can be prevented, especially hereditary ones, owners can take steps to reduce the risk and maintain joint health:

• Choose puppies from breeders who screen for patellar luxation and related orthopaedic conditions.
• Maintain a healthy body weight to reduce strain on joints.
• Avoid excessive jumping or twisting movements, especially in young or small dogs.
• Provide a balanced diet with adequate calcium, phosphorus, and essential fatty acids.
• Keep up with regular veterinary check-ups to catch early signs of joint instability.

Living with a Dog with Patellar Luxation

Dogs with patellar luxation can lead long, happy lives when managed properly. Owners should monitor for signs of pain, lameness, or difficulty rising and adjust activity levels as needed. Providing joint support through gentle exercise, a comfortable sleeping area, and weight control can significantly improve quality of life.

With modern veterinary care, even dogs requiring surgery can return to full, active lifestyles, often running, playing, and enjoying life as if the condition never existed.

Conclusion

Patellar luxation is a common yet manageable orthopaedic issue in dogs. With early diagnosis, appropriate treatment, and thoughtful long-term care, most dogs recover fully and remain active, happy companions. Awareness of the condition, especially in predisposed breeds, allows owners to act quickly, ensuring that their beloved pets continue to move with comfort, confidence, and joy throughout their lives.