Patellar Luxation in Dogs: Welfare and Treatment
Condition Overview
Patellar luxation (PL) occurs when the patella (kneecap) slips out of the trochlear groove of the femur, most commonly towards the inner aspect of the leg (medial patellar luxation, MPL). It is most common in small and toy breeds (Yorkshire Terrier, Pomeranian, Chihuahua, Bichon Frise, Boston Terrier). It is graded I-IV on the Putnam scale based on severity. It can be unilateral or bilateral. Large breeds more commonly develop lateral patellar luxation.
Welfare Impact by Grade
Grade I: patella occasionally luxates but self-reduces; minimal clinical signs; may not require treatment. Grade II: patella luxates more frequently; intermittent lameness (skipping gait on the affected leg); requires monitoring and possibly surgery. Grade III: patella permanently luxated but can be manually reduced; consistent lameness; surgical treatment recommended. Grade IV: patella permanently luxated and cannot be manually reduced; constant lameness; surgery required. Higher grades cause chronic pain, progressive joint disease, and welfare compromise if untreated.
Diagnosis and Assessment
Clinical examination (palpating the patella and assessing range of motion) grades PL. Radiography assesses bony deformities (trochlear groove depth, tibial crest position, patellar location). In moderate to severe cases, CT scan provides detailed 3D assessment of bony alignment. Assessment for concurrent hip dysplasia is important in large breeds. Bilateral assessment is essential as PL is frequently bilateral even if one side presents first.
Surgical Treatment
Surgery is indicated for grade II-IV PL causing clinical signs. Procedures typically combine trochlear groove deepening (trochleoplasty), tibial crest transposition (repositioning the tibial attachment of the patellar ligament), and lateral retinacular imbrication (tightening lateral supporting tissue). Outcomes are generally very good: most dogs return to normal function after appropriate surgery and rehabilitation. Specialist orthopaedic referral is appropriate for complex cases.
Prevention and Breeding
PL has a significant heritable component. Breeding dogs should be screened for PL (BVA/KC Patellar Luxation Scoring Scheme in the UK). Selecting against PL reduces prevalence in future generations. In predisposed breeds, maintaining healthy body weight reduces stress on affected stifles. Regular veterinary checks in at-risk breeds allow early identification and grading of PL before significant joint damage develops.