Growth plates, also known as epiphyseal plates, are areas of cartilage found near the ends of long bones in children and adolescents. These structures play a direct role in bone development, acting as sites where new bone tissue forms. They are fundamental for the lengthening of bones, allowing a child to grow taller. Understanding these regions provides insight into how the skeletal system matures.
Understanding Growth Plates
Growth plates are primarily composed of cartilage, a flexible tissue that differs from the hard, dense structure of mature bone. They are located at the ends of long bones, such as those in the arms and legs. Within these plates, cartilage cells continuously divide and create new cells. These new cells then gradually transform into solid bone, a process called ossification, which contributes to the bone’s overall length.
This process of cartilage production and subsequent ossification allows bones to grow longer as a child develops. Because growth plates are made of cartilage rather than hardened bone, they are softer and more vulnerable to external forces. This inherent difference in composition means they respond differently to stress compared to the fully formed bone found in adults.
Locating Growth Plates in the Ankle
In the ankle, growth plates are found within the long bones that form the ankle joint, specifically at the distal, or lower, ends of the tibia and fibula. The tibia, or shin bone, is the larger of the two lower leg bones and bears most of the body’s weight. The fibula is the thinner bone running alongside the tibia.
The growth plate of the distal tibia is situated just above the main ankle joint. It is a significant growth plate, accounting for a notable percentage of the overall growth in the lower leg. The distal fibula also contains a growth plate, located at its lower end near the outside bony prominence of the ankle, known as the lateral malleolus. These growth plates appear as distinct, darker lines on X-rays in growing individuals, indicating areas of cartilage that have not yet fully ossified into bone.
Why Ankle Growth Plates Are Important
The growth plates in the ankle control the lengthening and proper formation of the lower leg bones. Their continued function ensures that the tibia and fibula grow proportionately, which is essential for overall leg length and balanced ankle mechanics. This development helps support stable movement and weight-bearing activities.
These cartilaginous areas are weaker than the surrounding mature bone, ligaments, or tendons, making them more susceptible to injury. A fracture involving a growth plate can disrupt the normal bone-lengthening process. Such an injury, if not managed appropriately, may lead to altered bone growth, which could result in a limb that is shorter or has an atypical shape. Ankle growth plate injuries are common in children and adolescents participating in sports, often occurring from twisting motions.
Growth Plate Closure
As a child progresses through adolescence, growth plates undergo a natural process of closure, also known as epiphyseal fusion. During this stage, cartilage within the growth plate stops producing new cells and is replaced by solid bone. Once this fusion is complete, the bone can no longer lengthen.
This process typically occurs during the mid-to-late teenage years. For girls, growth plates usually close between ages 13 and 15, while for boys, closure often happens between ages 15 and 17. The distal fibula growth plate can be one of the last to close, sometimes between 15 and 18 years in females and 17 to 20 years in males. After closure, growth plate lines are no longer visible on X-rays, indicating that the bone has reached its adult length and increased its structural strength.