Patellar luxation is the most common orthopaedic condition in small dogs, ranging from clinically insignificant to severely painful and requiring surgical correction.
Patellar luxation welfare assessment requires careful differentiation between grade and clinical significance. Many grade I-II cases never cause clinical welfare harm and do not require surgical intervention. However, grade III-IV luxation causes genuine chronic pain from repeated cartilage trauma as the patella rides over the trochlear ridge. Dogs with significant luxation often show pain when the patella is displaced, hold the leg up periodically, and develop progressive gait abnormality. The decision to operate should be based on clinical welfare assessment - grading alone is insufficient. Surgery for clinically significant luxation provides excellent welfare outcomes with high success rates, preventing the progressive cartilage damage and osteoarthritis that untreated high-grade luxation produces.