The metaphysis is the wider portion of a long bone adjacent to the epiphyseal plate. It is this part of the bone that grows during childhood; as it grows, it ossifies near the diaphysis and the epiphyses. At roughly 18 to 25 years of age, the metaphysis stops growing and completely ossifies into solid bone. Epiphyseal plates ("growth plates") are located in the metaphysis and are responsible for growth in the length of the bone.

Because of their rich blood supply, metaphysis of long bones are prone to hematogenous spread of osteomyelitis in children. Metaphyseal tumors or lesions include osteosarcoma, chondrosarcoma, fibrosarcoma, osteoblastoma, enchondroma, fibrous dysplasia, simple bone cyst, aneurysmal bone cyst, non-ossifying fibroma, and osteoid osteoma.