Patella Luxation

Understanding Patella Luxation in dogs, a guide to diagnosis, treatment, and prevention

Dogs are known for their boundless energy and zest for life, but sometimes, underlying health conditions can hinder their mobility and overall well-being. One such condition that affects many canine companions is patella luxation.

Whether you’re a concerned dog owner seeking clarity about your beloved dog’s health, or a professional aiming to enhance your understanding of this condition, this article aims to provide valuable insights into managing patella luxation and improving the quality of life for dogs affected by it.

What is Patella Luxation?

Patella luxation, also known as luxating patella, is a condition where the kneecap (patella) dislocates or moves out of its normal position within the knee joint. This displacement can cause discomfort, pain, and difficulty in movement for affected dogs. It’s a common orthopedic issue, especially in certain breeds, and can range from mild to severe. Factors such as genetics, anatomy, and environmental influences can contribute to its development. Treatment options vary depending on the severity of the condition and may include medication, physical therapy, or surgical intervention to realign the patella and restore mobility.

Anatomy of the knee joint in dogs

The knee joint, also known as the stifle joint in dogs, is a complex structure that facilitates movement and weight-bearing in the hind limbs. Understanding its anatomy is crucial for comprehending conditions like patella luxation.

1. Femur (Thigh Bone): The femur is the long bone of the thigh. At its distal end (the bottom part), it forms two rounded condyles that articulate with the tibia to form the knee joint.
2. Tibia (Shin Bone): The tibia is the larger of the two bones in the lower leg. Its proximal end (the top part) forms the tibial plateau, which provides a surface for the femoral condyles to articulate with.
3. Patella (Kneecap): The patella is a small, flat, triangular bone located in front of the knee joint. It acts as a fulcrum, increasing the leverage of the quadriceps muscles during movement.
4. Quadriceps Muscles: The quadriceps muscles, including the vastus medialis, vastus intermedius, vastus lateralis, and rectus femoris, are located at the front of the thigh. These muscles contract to extend the knee joint and straighten the leg.
5. Patellar Ligament (Tendon): The patellar ligament is an extension of the quadriceps tendon that connects the quadriceps muscles to the tibia. It helps stabilize the patella and transmit the force of the quadriceps muscles to the lower leg.
6. Medial and Lateral Collateral Ligaments: These ligaments provide stability to the knee joint by connecting the femur to the tibia on the inner (medial) and outer (lateral) sides of the joint, respectively.
7. Cruciate Ligaments: The cranial (anterior) and caudal (posterior) cruciate ligaments are located within the joint capsule and help stabilize the knee by preventing excessive forward and backward movement of the tibia relative to the femur.
8. Menisci: The medial and lateral menisci are C-shaped cartilages located between the femoral condyles and tibial plateau. They act as shock absorbers, distributing forces within the joint and providing stability.

Understanding the intricate interplay of these structures is essential for diagnosing and treating conditions that affect the knee joint, such as patella luxation, cruciate ligament injuries, and osteoarthritis.

Symptoms and Diagnosis

Common Symptoms

Patella luxation can present a range of symptoms, which may vary in severity depending on the extent of the condition:

• Intermittent Limping: Dogs may suddenly begin to limp or show signs of lameness, which can come and go.
• Skipping: Affected dogs might skip or hop on three legs for a few steps before returning to a normal gait.
• Difficulty Extending the Leg: You might notice your dog having trouble fully extending its leg or experiencing stiffness, particularly after rest or exercise.
• Kicking the Leg Out: Dogs sometimes kick their leg outward to reposition the kneecap.
• Pain or Discomfort: Some dogs may show signs of pain or discomfort when the knee is touched or manipulated.

Veterinary Examination Techniques for Diagnosing

Diagnosing typically involves several key techniques:

• Palpation: During a physical examination, the veterinarian will manipulate the dog’s knee joint to feel for any abnormalities. This involves extending and flexing the leg to see if the kneecap (patella) moves out of its normal position. This can be done as young as 8 weeks old, and breeders of susceptible breeds should have this tested prior to the puppy going to its new home.
• Radiography (X-rays): X-rays are commonly used to get a detailed view of the knee joint and assess the severity of the luxation. This imaging technique helps in identifying any underlying bone deformities or joint issues.
• Grading the Luxation: Veterinarians often grade the severity of the luxation from I to IV, with Grade I being the mildest form where the patella can be manually luxated but returns to its normal position spontaneously, and Grade IV being the most severe, where the patella is permanently luxated.

Patella Luxation Grades

To accurately assess the severity of patella luxation and guide appropriate treatment strategies, veterinarians often classify it into different grades based on the degree of displacement and associated structural abnormalities.

Grade I

Grade I is the mildest form of the condition. In dogs with Grade I, the patella may occasionally slip out of its normal position, usually towards the inside (medial) of the knee joint, but it can be easily manipulated back into place by hand. Dogs may exhibit intermittent lameness or an occasional skipping gait, especially during physical activity. However, they often show minimal signs of discomfort and can continue to lead relatively normal lives.

Grade II

Grade II represents a moderate form of the condition. In this grade, the patella frequently dislocates from its groove within the femur, often with minimal manipulation. Dogs with Grade II luxation may display more pronounced lameness, reluctance to bear weight on the affected limb, and an altered gait characterized by a skipping or hopping motion. While they may still be able to walk and engage in light activity, the discomfort associated with patella instability becomes more noticeable.

Grade III

Grade III indicates a more severe form of the condition, where the patella remains luxated most of the time and can only be manually reduced into its normal position. Dogs with Grade III luxation typically experience significant lameness, pain, and difficulty in extending the affected limb. They may exhibit a crouching posture and may be reluctant to engage in physical activity due to discomfort. Without intervention, Grade III can lead to progressive joint degeneration and secondary complications such as osteoarthritis.

Grade IV

Grade IV is the most severe form of the condition, characterized by permanent displacement of the patella outside of its groove. In Grade IV the patella cannot be manually relocated into its normal position, and dogs experience persistent lameness, pain, and limited mobility. The affected limb may appear permanently flexed, and dogs may bear minimal weight on it. Grade IV often necessitates surgical intervention to realign the patella and restore joint stability, as conservative management alone may not effectively address the underlying structural abnormalities.

While mild cases may be managed conservatively with lifestyle modifications and supportive care, more severe cases often require surgical correction to alleviate pain, improve mobility, and prevent long-term joint damage. By accurately diagnosing and addressing the issues at an appropriate grade, veterinarians can enhance the overall health and well-being of affected dogs, allowing them to enjoy a more active and comfortable life.

Treatment Options

Managing and treating patella luxation in dogs involves various approaches, ranging from conservative management strategies to surgical interventions. The choice of treatment depends on the severity of the condition, the dog’s age, overall health, and specific needs.

Conservative Management Strategies

For mild cases of patella luxation or when surgery is not immediately necessary, conservative management strategies can be effective:

• Physical Therapy: Regular physical therapy can strengthen the muscles around the knee joint, improving stability and reducing the likelihood of luxation. Exercises may include controlled walking, swimming, and other activities designed to enhance muscle tone and joint function.
• Weight Management: Maintaining an optimal weight is crucial. Excess weight can put additional strain on the knee joint, exacerbating the condition. A balanced diet and regular exercise can help manage your dog’s weight effectively.
• Medications: Anti-inflammatory medications and pain relievers can be prescribed to manage pain and inflammation associated with patella luxation.
• Joint Supplements: Supplements containing glucosamine and chondroitin may support joint health and function.

Surgical Interventions

In more severe cases, or when conservative treatments fail to provide relief, surgical intervention may be necessary. Common surgical procedures include:

• Trochleoplasty: This procedure involves deepening the trochlear groove where the patella sits, allowing it to remain in place more securely.
• Tibial Tuberosity Transposition (TTT): TTT surgery repositions the tibial tuberosity, which changes the alignment of the patella tendon to keep the patella in its proper place.
• Lateral Imbrication: This technique tightens the soft tissues surrounding the patella to prevent it from luxating.
• Medial Release: In cases where the patella is being pulled too far medially (towards the inside), this procedure releases the tight tissues on the medial side of the patella.

What Factors Influence the Choice Between Conservative and Surgical Treatments?

Several factors influence the decision between conservative and surgical treatments:

• Severity of the Luxation: Mild cases (Grade I and II) often respond well to conservative management, while severe cases (Grade III and IV) typically require surgical intervention.
• Age and Activity Level: Younger, more active dogs or working dogs might benefit more from surgical correction to ensure long-term joint stability and functionality.
• Overall Health: Dogs with other health issues might be better managed conservatively if they are not good candidates for surgery.
• Response to Conservative Treatment: If a dog shows little improvement or continued pain and instability with conservative treatment, surgery might be recommended.

Are There Any Potential Complications Associated with Surgical Procedures?

While surgical procedures generally have high success rates, potential complications can include:

• Infection: As with any surgery, there is a risk of infection, which can usually be managed with antibiotics.
• Implant Issues: In cases where surgical implants are used, there can be problems such as loosening or breakage.
• Recurrence: There is a possibility that the patella may luxate again post-surgery, particularly if the underlying causes are not fully addressed.
• Anesthesia Risks: As with any surgery requiring anesthesia, there are inherent risks, especially in dogs with preexisting health conditions.

Resources

• The Kennel Club
• Cornell University