20 Jun Understanding Patellar Luxation in Dogs: Causes, Symptoms, and Treatment

Patellar luxation in dogs affects the kneecap, leading to discomfort and mobility issues. Understanding the causes, symptoms, and treatment options is crucial for owners to provide the best care for their lovely companions.

Types of Patellar Luxation in Dogs

• Medial Patellar Luxation (MPL)

Medial patellar luxation is the most common type of patellar luxation in dogs. In MPL, the patella dislocates towards the leg’s inside (medial side). This condition is more prevalent in small and toy breeds, such as Pomeranians, Chihuahuas, and Yorkshire Terriers, but it can also occur in larger breeds.

Congenital anatomical abnormalities, such as a shallow trochlear groove or malalignment of the quadriceps muscle, often cause MPL. These issues can cause the patella to slip out of its normal position. Trauma can also contribute to the development of MPL.

• Lateral Patellar Luxation (LPL)

Lateral patellar luxation is less common than MPL and involves the patella dislocating towards the leg’s outside (lateral side). LPL is frequently seen in larger dog breeds, such as Labrador Retrievers, German Shepherds, and Great Danes.

LPL can be caused by congenital abnormalities similar to MPL, including issues with the shape of the femur and the alignment of the quadriceps. Trauma or injury to the knee joint can also lead to LPL.

• Intermittent vs. Permanent Luxation

Intermittent Luxation

In intermittent luxation, the patella occasionally moves out of place and then returns to its normal position on its own. Dogs with intermittent luxation may show signs of lameness or discomfort periodically but can often walk normally most of the time.

Permanent Luxation

Permanent luxation occurs when the patella remains out of place and does not return to its normal position without intervention. This luxation often results in continuous pain, discomfort, and severe lameness. Dogs with permanent luxation usually require surgical correction to restore normal function.

Causes

• Inherited Traits: Genetic predisposition is one of the most significant causes of patellar luxation. Certain breeds are more prone to this condition due to inherited anatomical abnormalities. Small and toy breeds, such as Pomeranians, Chihuahuas, and Yorkshire Terriers, are particularly susceptible.
• Shallow Trochlear Groove: A shallow or improperly formed trochlear groove, where the patella sits typically, can cause the kneecap to slip out of place easily.
• Malalignment of Limb Structures: Malalignment of the femur, tibia, or quadriceps muscle can contribute to patellar luxation. When these structures are not correctly aligned, the forces acting on the knee joint can cause the patella to dislocate.
• Acute Injury: Trauma to the knee joint, such as a fall, collision, or sudden twist, can result in patellar luxation. Even dogs without a genetic predisposition can develop this condition due to an acute injury.
• Repetitive Stress: Repetitive stress on the knee joint, often seen in highly active or working dogs, can weaken the ligaments and other structures supporting the patella.
• Excess Weight: Carrying excess weight strains a dog’s joints, including the knees. Obesity can exacerbate existing anatomical abnormalities and increase the risk of patellar luxation.
• Weak Muscles: Dogs with poor muscle tone or weak muscles around the knee joint are more likely to experience patellar luxation. Solid and well-developed muscles help stabilize the patella and keep it in place.
• Hip Dysplasia: Hip dysplasia, another common orthopaedic condition, can contribute to patellar luxation. Dogs with hip dysplasia may alter their gait to compensate for hip pain, leading to abnormal stress on the knee joint and increased risk of luxation.
• Legg-Calvé-Perthes Disease: This condition, characterized by the degeneration of the femoral head, can indirectly lead to patellar luxation. As the femoral head deteriorates, the stability of the entire leg is compromised, making patellar luxation more likely.

Preventive Measures

1. Genetic Testing and Responsible Breeding: To prevent patellar luxation, breeders must perform genetic testing and avoid breeding dogs with a history of the condition. This practice helps reduce the prevalence of patellar luxation in future generations.
2. Maintaining a Healthy Weight: Keeping your dog at a healthy weight through proper diet and regular exercise can reduce the strain on their joints and decrease the risk of developing patellar luxation.
3. Strengthening Exercises: Engaging your dog in exercises that strengthen the muscles around the knee joint can help provide better support for the patella. Activities like swimming and controlled walking can be beneficial.
4. Avoiding High-Impact Activities: Limiting activities involving jumping or sudden direction changes can prevent trauma to the knee joint. Ensure your dog’s exercise routine is appropriate for their breed, age, and physical condition.

Symptoms of Patellar Luxation

• Skipping Gait: A characteristic skipping gait is one of the most common signs of patellar luxation. Dogs may hold up their leg for a few steps.
• Sudden Limping: Dogs with patellar luxation may suddenly start limping, especially after physical activity. This limping can come and go.
• Hopping: In more severe cases, dogs may exhibit a hopping gait, consistently favouring one leg and using a hopping motion to move.
• Stiff Leg Movement: Dogs with patellar luxation might show stiffness in their leg movements. This is due to the discomfort and instability.
• Avoiding Physical Activity: Affected dogs often become reluctant to engage in physical activities. Patellar luxation makes these activities challenging and unenjoyable.
• Difficulty Standing Up: Dogs with patellar luxation may have trouble standing up from a sitting or lying position.
• Signs of Pain: Dogs with patellar luxation might show signs of pain, such as whining, whimpering, or yelping, especially when their knee is touched or manipulated.
• Restlessness: Due to the discomfort, dogs may become restless. They also have difficulty finding a comfortable position to lie down.
• Thigh Muscle Wasting: Chronic patellar luxation in dogs can lead to muscle atrophy, particularly in the thigh muscles.
• Reduced Muscle Tone: The overall muscle tone in the affected leg can decrease due to reduced use and ongoing discomfort.
• Bowed Legs: In severe cases, the constant dislocation of the patella can cause the legs to appear bowed or deformed.
• Swelling: Visible swelling around the knee joint may indicate inflammation and irritation from repetitive patellar dislocation.
• Increased Irritability: Chronic pain and discomfort caused by patellar luxation can affect their overall mood and behaviour.
• Loss of Appetite: Pain can also lead to a loss of appetite. It could be a sign that they are experiencing significant discomfort.

Diagnosing Patellar Luxation

1. Medical History: The diagnosis begins with a thorough medical history. The veterinarian will ask about the dog’s symptoms, including when they started, their frequency, and any changes in behaviour or activity level. Details about previous injuries or conditions that may contribute to knee problems are also important.
2. Physical Examination: A hands-on physical examination is essential. The veterinarian will palpate the knee joint to assess its stability and detect any signs of pain or discomfort. They will manipulate the knee to check if the patella can be luxated manually and whether it returns to its normal position.
3. Observation of Movement: The veterinarian will observe the dog’s walking and running gait. They look for signs of lameness, skipping gait, or abnormal leg movement indicative of patellar luxation. This observation helps assess the severity of the condition.
4. Lameness Evaluation: Evaluating the degree of lameness is crucial. The veterinarian may ask the dog to perform specific movements, such as walking in a straight line, turning, or climbing stairs, to identify the extent of the problem.
5. X-rays: X-rays are a fundamental diagnostic tool for patellar luxation. They provide detailed images of the knee joint, allowing the veterinarian to assess the patella’s alignment, the trochlear groove’s depth, and any bone abnormalities or signs of arthritis.
6. Ultrasound: Ultrasound imaging can evaluate the soft tissues around the knee joint, including the ligaments and muscles. It is beneficial for identifying any underlying issues contributing to patellar luxation.
7. MRI and CT Scans: Advanced imaging techniques like MRI (Magnetic Resonance Imaging) or CT (Computed Tomography) scans may be employed in more complex cases. These provide high-resolution images of bone and soft tissue structures, offering a comprehensive view of the knee joint.

Grading Patellar Luxation

• Grade 1: When released, the patella can be manually luxated but returns to its normal position. Dogs may show no signs or only occasional lameness.
• Grade 2: The patella luxates with movement but returns to the groove spontaneously or with manual manipulation. Dogs may show intermittent lameness and a skipping gait.
• Grade 3: The patella is luxated most of the time but can be manually reduced. Dogs often exhibit persistent lameness and difficulty in movement.
• Grade 4: The patella is permanently luxated and cannot be manually reduced. Severe lameness and abnormal limb alignment are joint.

The Last Word

Patellar luxation is a common orthopaedic condition in dogs that requires early detection and appropriate management. With a comprehensive understanding of this condition, pet owners can ensure their dogs receive the necessary care to maintain a good quality of life.