Patellar luxation — dislocation of the kneecap — is among the most common orthopaedic conditions in small and toy breed dogs, causing pain and lameness that varies from mild to severe depending on grade.
Patellar luxation welfare implications depend critically on grade. Grade 1 animals that are not lame may need only monitoring. Grade 2-4 animals, however, experience varying degrees of chronic pain and gait abnormality that impairs their quality of life — higher-grade cases involve persistent lameness that prevents normal activity. Surgical correction in appropriate candidates reliably improves welfare, with most dogs returning to normal or near-normal function. Delaying surgery in symptomatic Grade 3-4 cases allows progressive cartilage damage that worsens long-term outcomes. Breeding of dogs with Grade 3-4 patellar luxation should be avoided — the condition has a significant heritable component.