Normally the kneecap glides in a groove at the front of the knee joint as the dog bends and straightens its leg. With patellar luxation it shifts to the side, most often towards the inside of the knee. The condition is often linked to how the bones, muscles and tendons around the knee joint are shaped and have developed. It is common in smaller breeds but can also affect larger dogs.
A classic sign is that the dog suddenly holds up a hind leg for a few steps and then starts walking normally again. Other dogs get longer-lasting lameness, stiffness or reluctance to run and jump. The vet examines how stable the kneecap is and usually grades the luxation from grade I to IV. With more pronounced problems, X-rays or other imaging may be needed to assess the shape of the bones and plan the treatment.
Not every dog with patellar luxation needs surgery. A dog with mild luxation and no or few symptoms can sometimes be monitored without surgery. With recurring lameness, pain or obvious malalignment, an operation may be appropriate. The surgery is adapted to the anatomical changes present and can involve deepening the kneecap's groove, moving the tendon attachment, correcting the soft tissues around the knee joint or changing the angle of the bone. So there is no single operation that suits every dog.