PATELLAR luxation is a commonly seen orthopaedic problem in veterinary practice. Diagnosis of the condition is usually straightforward. However, a knowledge of the normal anatomy, function and interrelationship between the hip and stifle joints, femur, tibia and soft tissues is necessary if the surgeon is to choose the most appropriate method of treatment. This article describes medial and lateral patellar luxation, the clinical signs, diagnosis and treatment options available in the dog and cat.