Biometry is a new working method for elucidating the causes of the phenomenon of reproducible movement in biology. The methodology of biometry allows for the spatial development of the knee control system a priori from the length ratio of the cruciate ligaments of the knee joint and the specific length measurement of the posterior cruciate ligament, determining leg length and the corresponding body height, and deriving the hip joint from the knee control system. The insight that the unknown biological movement systems embody self-actualizing, biometrically free laws is groundbreaking for all disciplines that deal with the living.