An epiphyseal line on a bone indicates what?

Long bones possess a cartilaginous zone between the diaphysis (midsection) and the epiphysis (end) called the epiphyseal plate. During childhood this allows the bone to continue growing in length. At some point the cartilage ossifies (becomes bone tissue), leaving a line of demarcation, the epiphyseal line. This indicates the bone has reached its adult length and no further growth in length will occur. However, the bone can continue to grow in diameter.