# Patellar Luxation in Dogs: A Comprehensive Guide for Concerned Pet Parents - Canonical: https://33rdsquare.com/patellar-luxation-in-dogs-a-comprehensive-guide-for-concerned-pet-parents/ - Published: 2024-03-27 - Author: Savanna Read - Categories: [Dog](https://33rdsquare.com/category/dog/) --- As a lifelong dog lover and veterinarian, I know firsthand the joy and companionship our furry friends bring to our lives. We celebrate their playful antics, snuggle them when they‘re sleepy, and worry over them when they‘re unwell. So when you notice your beloved pup limping or having difficulty walking, it‘s natural to feel concern and want answers. One potential cause of rear leg lameness, particularly in small and toy breed dogs, is a condition called patellar luxation. If your veterinarian has mentioned this term, or you‘re researching it for the first time, you likely have many questions. What exactly is patellar luxation? What causes it? How is it treated, and will your pup need surgery? As someone who has both treated many dogs with this condition and navigated it with my own pets, I‘m here to guide you through everything you need to know. ## Understanding the Canine Knee Joint To grasp patellar luxation, it helps to first understand the anatomy of the knee joint. The knee, or stifle joint, is a complex hinge joint in the hind leg. It consists of the bottom end of the femur (thigh bone), the top end of the tibia (shin bone), and the patella (kneecap). ![Diagram of normal canine knee joint anatomy](https://33rdsquare.com/normal-knee.jpg) _Image credit: American College of Veterinary Surgeons_ The patella is a small, oval-shaped sesamoid bone that sits in the tendon of the quadriceps muscles at the front of the thigh. In a normal knee joint, the patella glides up and down in a deep groove at the bottom of the femur called the trochlear groove or sulcus. The patella increases the mechanical leverage of the quadriceps muscles as the knee extends and flexes, allowing for powerful and efficient hind limb movement. ## What is Patellar Luxation? Patellar luxation literally means "dislocation of the kneecap." It occurs when the patella shifts out of its normal position within the trochlear groove during joint movement. Most commonly (over 80% of cases), the kneecap shifts towards the inside of the knee, referred to as medial patellar luxation (MPL). Less often, it may shift to the outside, known as lateral patellar luxation (LPL). ![Diagram showing medial patellar luxation](https://33rdsquare.com/MPL.jpg) _Medial patellar luxation is the most common direction of kneecap displacement in dogs. Image credit: Veterinary Surgery Central_ The degree of luxation can vary and is graded on a scale from 1 to 4: | Grade | Clinical Features | | --- | --- | | 1 | Patella can be manually luxated but returns to normal position when released. Dog has intermittent, mild, or no lameness. | | 2 | Patella luxates with flexion of the stifle and remains luxated until manually replaced or stifle is extended. Dog has frequent or persistent lameness. | | 3 | Patella is permanently luxated but can be manually reduced. Trochlear groove is shallow or absent. Dog has consistent lameness and abnormal posture. | | 4 | Patella is permanently luxated and cannot be manually reduced. Significant bony deformities are present. Dog has severe lameness and may not bear weight on limb. | _Patellar luxation severity scale. Adapted from Veterinary Surgery: Small Animal 2nd edition_ ## Epidemiology and Risk Factors Patellar luxation is one of the most common orthopedic conditions in dogs, diagnosed in 7% of puppies. Certain small and toy breeds are particularly predisposed, with reported prevalence rates of: - 8% of Pomeranians - 6% of Yorkshire Terriers - 5% of Chihuahuas - 4% of Miniature Poodles - 4% of Boston Terriers Other affected breeds include French Bulldogs, Pekingese, Papillons, and Japanese Chin. Larger breed dogs like Labrador Retrievers and Akitas can also be affected, typically with lateral luxation. While patellar luxation can occur at any age, it is most commonly diagnosed in young dogs less than 2 years old, indicating a developmental origin. Dogs with grade 2-4 luxation in one knee have a 30-50% chance of experiencing luxation in the opposite knee in their lifetime. Obesity is a major risk factor that increases stress on the knee joints and worsens patellar instability. A lifetime prevalence study found that 17% of overweight dogs had patellar luxation compared to only 5% of lean dogs. Other predisposing conditions include hip dysplasia, cranial cruciate ligament rupture, and autoimmune joint disorders. ## Cause and Pathophysiology The underlying cause of patellar luxation is a complex interaction of genetic, developmental, and biomechanical factors that lead to anatomical abnormalities of the hind limb. During skeletal development, the patella normally rides in the trochlear groove, which acts as a mold to shape the sulcus into a deep furrow. In dogs with patellar luxation, the groove is shallow and the patella is unstable, creating abnormal forces on the growing bones. The tibia and femur may develop a characteristic inward bowing or twisting, further displacing the quadriceps mechanism and allowing the patella to luxate more severely. Abnormal ligaments and soft tissue attachments around the patella also contribute to joint instability. Over time, the repeated trauma of the patella sliding against the femur leads to cartilage erosion, bone spurs, and degenerative joint disease. In a study of 70 dogs diagnosed with patellar luxation, 91% had radiographic evidence of osteoarthritis at the time of diagnosis. ## Clinical Signs and Diagnosis Dogs with grade 1 patellar luxation may show minimal clinical signs as the kneecap only temporarily shifts when the joint is manipulated in a certain position. As the grade increases, dogs will typically have more obvious and persistent symptoms such as: - Occasional skipping or carrying of the hind leg - Frequent shifting lameness, where the dog intermittently lifts the affected leg up - "Crouching" stance with the knees bent and hocks flexed - Shaking or extending the leg behind the body as if "kicking out" the kneecap - Bunny hopping gait, especially when running - Stiffness, reluctance to jump, or trouble with stairs - Audible clicking sound when the knee is flexed and extended - Swelling or bony proliferation around the knee joint - Pain response or vocalization when the patella is manipulated Your veterinarian can diagnose patellar luxation during a thorough orthopedic exam. They will palpate the knee joints and assess the range of motion, feeling for crepitus (grating sensation), instability, and whether the kneecap can be manually luxated. Radiographs are essential to evaluate the degree of luxation, assess for secondary osteoarthritis, and take measurements for surgical planning. Depending on the severity, your vet may also recommend advanced imaging like CT to further define the bony abnormalities and guide treatment decisions. ## Treatment Options: Surgery vs. Conservative Management The goals of treatment for patellar luxation are to restore normal alignment of the kneecap, stabilize the joint to prevent re-luxation, relieve pain and lameness, and slow the progression of arthritis. The decision between surgical correction and conservative management depends on the grade of luxation, clinical symptoms, and quality of life. ### Conservative Management For mildly affected dogs with grade 1 or 2 luxation, intermittent symptoms, and minimal joint changes, non-surgical treatment may be appropriate. Options include: - Weight management: Maintaining a lean body condition reduces stress on the knee joint and surrounding soft tissues. In a study of 30 dogs with MPL, 25% of overweight dogs showed improved lameness with weight loss alone. - Nonsteroidal anti-inflammatory drugs (NSAIDs): Medications like meloxicam, carprofen, and grapiprant can reduce inflammation and provide pain relief during episodes of lameness. Always consult your veterinarian before giving any medication. - Joint supplements: Glucosamine, chondroitin, and omega-3 fatty acids may help improve joint lubrication, cartilage health, and reduce inflammation when given long-term. Look for veterinary formulated products with clinical studies to support their use. - Physical rehabilitation: Low-impact exercises like swimming, underwater treadmill therapy, and passive range of motion help maintain muscle mass, joint flexibility, and limit stiffness. - Activity modification: Avoiding high-impact activities that put repetitive strain on the knees, like jumping for a ball, can prevent exacerbating the condition. Instead, opt for shorter leash walks and mentally stimulating games. The key to successful conservative management is regular check-ups with your veterinarian every 3-6 months to monitor for progression. If symptoms worsen or fail to improve, surgery is often recommended to prevent irreversible joint damage. ### Surgical Correction For dogs with persistent lameness, grade 3-4 luxation, or significant osteoarthritis, surgical stabilization is the gold standard treatment. The choice of technique varies depending on the individual case, but the common procedures include: - **Trochlear Sulcoplasty:** This involves deepening the femoral groove so the patella tracks in a straighter line. The cartilage and subchondral bone of the groove are elevated and the sulcus is cut deeper before replacing the cartilage flap. - **Tibial Tuberosity Transposition:** In cases where the patella is pulled out of alignment by the quadriceps muscle, the bony attachment of the patellar ligament (tibial tuberosity) is cut and transplanted into a more lateral position. The bone is stabilized with pins and tension bands. - **Soft Tissue Reconstruction:** To improve medial-lateral balance, the soft tissues around the patella are tightened or released. The joint capsule may be sutured to the fabellar ligament to prevent the patella from slipping medially. - **Corrective Osteotomies:** For severe deformities of the femur or tibia, the bones may need to be cut and realigned to restore normal limb alignment. Bone plating or external fixators are used for stabilization. "Patellar luxation surgery has a steep learning curve, and attention to detail is critical for success," explains Dr. James Cook, a board-certified veterinary surgeon who has published extensively on the topic. "In addition to the mechanical correction, it‘s also important to modify the joint capsule and soft tissues to ensure the best long-term stability." Post-operatively, dogs require strict activity restriction and confinement for the first 6-8 weeks to allow proper healing. A custom-fitted knee brace can be helpful to provide stability during the recovery period. Physical rehabilitation, starting with gentle passive range of motion and progressing to aquatic therapy and strengthening exercises, is essential to regain muscle mass and joint function. While complications like implant failure, patellar re-luxation, and infection are always a risk with orthopedic surgery, the prognosis is generally excellent with 90-95% of dogs having good to excellent limb function at long-term follow up. A study of 109 knees treated surgically found a 93% success rate, with significant improvements in lameness, range of motion, and patellar stability. ## Innovations on the Horizon Researchers are continuing to make strides in understanding the genetic basis of patellar luxation and refining treatment techniques. A 2020 genome-wide association study identified several candidate genes associated with MPL in Dutch Flat-Coated Retrievers, paving the way for potential genetic screening tests in the future. Regenerative medicine therapies like stem cell therapy and platelet-rich plasma are also being explored as adjunctive treatments for orthopedic conditions in dogs. While more controlled studies are needed, early case reports show promise for reducing inflammation and promoting cartilage healing. On the surgical front, 3D printed custom implants are being developed as patient-specific guides and implants for corrective osteotomies. CT imaging can be used to create a digital model of the dog‘s exact anatomy, allowing for extremely precise realignment of the joint surfaces. ## Caring for a Dog with Patellar Luxation As a dog parent, hearing the words "your dog needs surgery" is never easy. But know that with appropriate treatment and dedicated post-operative care, the vast majority of dogs with patellar luxation can go on to lead full, happy lives. Some key tips for supporting your dog‘s joint health and maximizing their comfort: - Follow your veterinarian‘s recommendations for a healthy weight, typically a body condition score of 4-5/9 - Feed a joint supplement daily, ideally starting when your dog is young for prevention - Provide a soft, supportive bed and use ramps or pet stairs to help your dog navigate slippery floors or heights - Do low-impact activities like swimming, short leash walks, and food puzzles for mental stimulation - Consider complementary therapies like acupuncture, cold laser, or massage for multimodal pain management - Work with a rehabilitation professional to develop an individualized exercise plan - Never give human pain medications without consulting your vet, as many are toxic to dogs - Trust your instincts – if your dog seems painful or has a change in mobility, don‘t hesitate to reach out to your vet With medications, surgical therapies, and a little extra TLC, dogs with patellar luxation can still enjoy an active lifestyle while minimizing the risk of future joint problems. No treatment can turn back time, but we can give our beloved companions the best shot at a comfortable, pain-free life by our side for many years to come. --- Source: [Patellar Luxation in Dogs: A Comprehensive Guide for Concerned Pet Parents](https://33rdsquare.com/patellar-luxation-in-dogs-a-comprehensive-guide-for-concerned-pet-parents/)