Patellar luxation is a common orthopaedic condition in small and toy breeds, causing intermittent lameness and chronic pain that affects quality of life.
Patellar luxation welfare impact varies enormously by grade. Grade I dogs that occasionally skip on one leg may experience minimal welfare compromise, while grade IV dogs with permanently luxated patellas suffer chronic pain and cannot extend their knee normally. The progressive nature of higher-grade luxations - where repeated episodes cause cartilage damage and secondary osteoarthritis - means that welfare deteriorates over time without intervention. The heritable component of the condition in many small breeds means breeding selection should prioritise patellar conformation. Breed health surveys and pre-breeding patellar grading schemes help reduce the burden of this condition in future generations.