Why is it so hard to grow the shin bone once growth plates have closed?

Finished growing: Bone lengthening occurs at the ends of the long bones at the site of the growth plates. If the growth plates have closed, no more lengthening can occur.

See below: Growth plates are areas of special cartilage within bones to allow the skeleton to grow longer and wider with time. Once the growth plates are closed, the bone has the capacity to heal but not to add ;length. This keeps us from growing our whole lives and getting bigger than our skeletons will support.