The patella (kneecap) normally rides in a groove called the trochlea at the end of the femur bone. When the patella luxates or moves out of the groove, the knee joint cannot flex properly.
Patellar luxation is usually caused by a conformational abnormality at the level of the hip joint and results in abnormal forces that act on the kneecap causing it to ride outside the groove. In young animals, the groove becomes very shallow and the attachment of the patellar ligament is often malpositioned on the tibia (shin bone). The kneecap most often luxates to the inner aspect of the knee joint and is called medial patellar luxation.
Clinical signs can include; lameness, pain, intermittent skipping when running or walking, and/or stiffness in the affected leg. Surgery is indicated to reduce the incidence of arthritic changes due to instability within the knee joint.
In most cases, a series of two surgical steps are taken to properly align the patella. If the groove is shallow or misshapen, it is surgically deepened to allow the patella to sit deeper within the femur. Replacement cartilage (fibrocartilage) will gradually fill in the re-contoured portion of bone. Secondly, the joint capsule and surrounding muscle along the side of the patella are often stretched during a luxation. These tissues are sutured or tightened on the opposite the side of the luxation to provide additional support and prevent abnormal movement of the patella.
Approximately 90% of our patients will return to normal function of the limb. Surgery is designed to address the luxating patella, but cannot reverse arthritic changes that are already present in the knee joint. Patients with arthritic knees may have some stiffness after rest or may become lame after heavy exercise. Some patients with a severe luxation are at risk for reluxating after surgery. Fortunately, this is not common for most pets. To schedule an appointment for a surgical consultation please call our office at 715-268-8131.