In children, some bones are comprised of several parts, to allow for growth, which will eventually fuse on maturity. As the pattern of growth and fusion is closely related to age, the stage these bones have reached is a reliable guide. The adult human femur (thigh bone), for example, is a single bone but in children it consists of four different components: shaft, distal articular end (at the knee), a proximal articular head (at the hip) and the greater trochanter on the side of the bone where the muscles attach.
