Growth plates are areas of developing cartilage tissue near the ends of long bones. When a child becomes full-grown, the growth plates harden into solid bone.
Because growth plates are the last portion of bones to harden (ossify), they are vulnerable to fracture.
Growth plates regulate and help determine the length and shape of adult bone, therefore, injuries to the growth plate can result in disturbances to bone growth and bone deformity.
Growth plate injuries occur most often in contact sports like football or basketball and in high impact sports like gymnastics. Source: http://orthoinfo.aaos.org/topic.cfm?topic=A00056