Medicine
Growth Plates (Epiphyseal Plates)
Quick fact
A single growth plate can produce up to 1 cm of new bone per year during peak growth, and all plates close by the end of puberty, setting your final adult height.
Why this is interesting
You may have noticed that children grow taller almost overnight—but how exactly do bones get longer?
Read the full explanation
Understanding Growth Plates (Epiphyseal Plates)
Imagine a ladder that extends by adding new rungs at one end. Long bones like the femur or humerus grow in a similar way. At each end of a growing bone, there is a thin layer of cartilage called the growth plate (or epiphyseal plate). This cartilage is not static—its cells, called chondrocytes, are constantly dividing and enlarging. As these cells multiply and produce new cartilage matrix, the plate thickens. On the bone side, the older cartilage is gradually replaced by hard bone through a process called ossification. The net effect is that the bone lengthens from the ends, like a conveyor belt of cartilage converting to bone. Growth plates are the reason children can grow for years before the plates eventually close and are replaced by solid bone near the end of puberty.
A deeper explanation
The mechanism behind growth plates is a carefully regulated sequence of endochondral ossification. In the resting zone at the top of the plate, chondrocytes are stored. When growth signals (like growth hormone and IGF-1) arrive, these cells enter a proliferative zone, where they rapidly divide, stacking into columns. Next, they enter the hypertrophic zone, swelling up dramatically. This enlargement alone pushes the bone ends apart. Finally, the cells undergo apoptosis (programmed cell death), and the surrounding cartilage matrix becomes calcified. Blood vessels and bone-forming cells (osteoblasts) invade this calcified framework, depositing bone mineral and replacing the cartilage with trabecular bone. The growth plate itself remains a cartilaginous island until near the end of puberty, when estrogen and other hormones cause the plate to undergo its own calcification and seal shut—a process called epiphyseal closure. This is why injuries to growth plates in children can alter bone length or shape, requiring specialized orthopedic care.