The vertical position of the patella. A new radiographic method for routine use.

Patella height was defined by the distance between the midpoint of the articular surface of the patella and the condylar plane, which was constructed perpendicular to the mechanical axis of the tibia. In two series of normal individuals the measured distances were related to body height and the length of the lower leg and thus expressed as its ratio, which was the same in both sexes. The measurements were performed on lateral radiographs of the knee and lower leg obtained in weight-bearing and 30 degrees to 40 degrees of knee flexion using a simple device to obtain a standardized position of the lower leg during the examination. The standing position is proposed for these measurements since the patellar ligament is shorter in the recumbent position. The method can be used for biomechanical analysis of the femoropatellar joint.