Roentgenographic and experimental studies of the patella alta

: Patella alta has so far been given attention with reference to the patellofemoral disorder. However, neither its morphological concept has been quite coherent yet nor its clinical significance has been fully understood. In order to clarify these points, the author made a roentgenographic investigation of patella alta and also conducted an experimental study. Defining as patella alta the condition in which the articular surface of the patella is higher than the patellar surface on the femur, the author evaluated the patella position by seizing, from the dynamic viewpoint, the positions of the articular surface of the patella to the patellar surface on the femur by serial roentgenography and their graphic representations. The results obtained revealed that in the patellofemoral osteoarthritis, compared with the normal, there was observed retarded descending of the patella into the femoral intercondylar notch at knee flexion. Moreover, on the rabbit knee whose patellar ligament was lengthened, descending condition of the patella similar to that observed for human patellofemoral osteoarthritis was created, thus leading to an experimental patellofemoral osteoarthritis. The above results suggested an of important role of patella alta in the pathogenesis of patellofemoral osteoarthritis.