Growth plates are the primary sites for bone lengthening in children and adolescents, responsible for increasing height and skeletal development. Understanding these areas is important for appreciating how the body grows and how certain injuries can affect that process.
Understanding Growth Plates
A growth plate, also known as an epiphyseal plate or physis, is a layer of cartilage found near the ends of long bones in growing individuals. Long bones include those in the legs (femur, tibia), arms (radius, ulna), hands, and feet. Each long bone has two growth plates, positioned between the main shaft of the bone, called the diaphysis, and the bone’s rounded end, known as the epiphysis.
Composed of cartilage, growth plates are softer than the solid bone that surrounds them. This cartilaginous nature allows them to be areas of active growth. Their location at the ends of bones facilitates the lengthening process throughout childhood and adolescence.
How Growth Plates Drive Bone Growth
Bone lengthening occurs within the growth plates through a mechanism called endochondral ossification. Within the growth plate, cartilage cells, known as chondrocytes, continuously divide and multiply, forming new cells. These new cells are pushed towards the main part of the bone, where they mature and enlarge.
As these older cartilage cells degenerate, the surrounding matrix becomes calcified, and blood vessels invade the area. Specialized bone-forming cells, called osteoblasts, then replace the calcified cartilage with new bone tissue, adding length to the bone. This process is regulated by various factors, including systemic hormones like growth hormone, which stimulates chondrocyte growth, and estrogen, which influences the maturation and eventual closure of the growth plate.
Growth plate closure, or epiphyseal fusion, marks the end of longitudinal bone growth. At this stage, near the end of puberty, the cartilage in the growth plate is completely replaced by solid bone, leaving behind an epiphyseal line. For girls, this occurs between ages 13 and 15; for boys, between 15 and 17 years old. Once the growth plates have fused, further lengthening of the bones is no longer possible.
Growth Plate Injuries
Growth plates are susceptible to injury in children and adolescents because their cartilaginous structure is weaker than the surrounding mature bone, ligaments, and tendons. An impact that might cause a sprain in an adult could result in a growth plate fracture in a child. Common causes of these injuries include falls, sports-related accidents, and repetitive stress from activities like throwing.
Unlike typical bone fractures, damage to a growth plate can affect future bone development. An improperly healed growth plate injury can lead to complications such as limb length discrepancies, where one limb becomes shorter than the other, or angular deformities, causing the bone to grow crookedly. Prompt medical evaluation is important if a growth plate injury is suspected, as early and proper treatment can mitigate long-term issues and promote normal bone growth.