Understanding Growth Plates: When and Why Bone Growth Stops in Teenagers

Growth plates are the key to height, dictating when and why our bones stop lengthening as we transition from childhood to adulthood.

By Garret Merkley · Explainer · Jun 9, 2026

Branched from Growth Hormone Therapy and Height: What Modern Medicine Can and Cannot Do

Quick take

Growth plates are cartilage at the ends of long bones where new bone is made, allowing bones to lengthen.
Puberty's hormones, especially estrogen, trigger the eventual fusion (closure) of these plates.
Once growth plates close, bones can no longer lengthen, and height gain stops.
Girls typically experience growth plate closure earlier than boys, usually between 14-16 for girls and 16-18 for boys.

Growth plates, also known as epiphyseal plates, are specialized areas of cartilage located near the ends of long bones in children and adolescents. These plates are essentially factories where new bone tissue is produced, allowing bones to grow longer and, in turn, increasing a person's height.

How Growth Plates Work: The Cartilage-to-Bone Process

Within each growth plate, cartilage cells (chondrocytes) multiply and expand, pushing the ends of the bone further apart. As these cartilage cells mature, they are gradually replaced by bone-forming cells (osteoblasts) that deposit new bone matrix. This continuous process of cartilage formation and subsequent bone replacement is what makes bones lengthen during childhood and adolescence. It's a highly organized and regulated system, ensuring steady and symmetrical growth across the body.

The Hormonal Signal: When Growth Plates Close

The eventual closure of growth plates is a crucial biological event, primarily driven by the surge of sex hormones during puberty. Both estrogen and testosterone play vital roles. While testosterone directly promotes growth, it's estrogen (present in both sexes, though in higher concentrations in females) that is the primary signal for growth plate fusion. Initially, these hormones stimulate growth, leading to growth spurts. However, as hormone levels rise and remain high throughout puberty, they signal the cartilage cells in the growth plates to stop multiplying and to fully convert into solid bone. This process is called epiphyseal fusion or growth plate closure. Once the cartilage is entirely replaced by bone, the growth plate disappears, leaving behind a faint line called an epiphyseal line, and no further lengthening of that bone can occur.

Generally, girls experience this closure earlier than boys, typically between ages 14 and 16, due to their earlier onset of puberty and the earlier, higher surge of estrogen. Boys' growth plates usually close later, between ages 16 and 18.

Understanding growth plates is fundamental because they are the sole determinant of a person's final adult height. Once these plates have fused, any further increase in height from bone lengthening is impossible. This knowledge is critical in medicine for several reasons: predicting adult height, diagnosing growth disorders, and managing fractures in children. A fracture that damages a growth plate in a child can potentially interfere with future bone growth, leading to limbs of unequal length or bone deformities, making careful treatment essential.

Can growth plates reopen once they've closed?

No, once growth plates have fully fused and turned into solid bone, they cannot reopen. The bone has reached its maximum length from that point, and no further height can be gained from bone lengthening.

How do doctors check if growth plates are still open?

Doctors typically use X-rays to check the status of growth plates. On an X-ray, open growth plates appear as distinct dark lines or gaps near the ends of bones, because cartilage does not show up as dense as bone. Fused growth plates appear as solid bone or a faint line, indicating closure.

Do all bones have growth plates?

Growth plates are primarily found in the long bones of the body, such as those in the arms, legs, fingers, and toes. Other bones, like those in the skull or vertebrae, grow differently and do not have classic growth plates.

Can diet or exercise affect growth plate closure?

While a healthy diet and regular exercise are crucial for overall bone health and development, they do not directly alter the timing of growth plate closure, which is primarily genetically and hormonally determined. However, severe malnutrition can impair growth, and excessive, repetitive stress or injury to a growth plate can potentially damage it and affect future growth.