Why does bone growth in length stop after the growth plates are replaced by bone?

Longitudinal bone growth relies on the epiphyseal plate, a region of cartilage located at the ends of long bones. Within this plate, cartilage cells continuously replicate and undergo a complex process of degeneration, calcification, and replacement by bone from the shaft side. This mechanism allows the bone to extend in length.12

Bone growth in length stops because the epiphyseal plates are not permanent structures; they are designed to persist only until the bone reaches its full adult length. Upon reaching skeletal maturity, these plates undergo fusion and are entirely replaced by bone. This closure is triggered by sex hormones, such as testosterone in males and estrogens in females, which increase significantly during puberty. Once the cartilage is replaced by bone, the mechanism for longitudinal extension is eliminated, and the bone can no longer grow in length.213