Growth Plates: What They Are and When They Close

Growth plates are areas of soft cartilage near the ends of long bones, such as the thighbone and shinbone, where new bone is made while kids and teens grow. They usually close, meaning they harden into solid bone, near the end of puberty: around ages 13 to 15 for girls and 15 to 17 for boys. Once a growth plate has closed, that bone cannot get any longer.

What are growth plates?

A growth plate (doctors call it the physis or epiphyseal plate) is a thin layer of cartilage, a rubbery, flexible tissue, that sits between the shaft of a bone and its rounded end. It is where a bone adds length, and it also helps set the bone's final shape.

Most long bones have at least two growth plates, one near each end. Because cartilage is softer than bone, growth plates are the weakest part of a growing skeleton. They are even weaker than the ligaments and tendons around them, which is why a fall that would sprain an adult's ankle can break a child's bone at the growth plate instead.

Where are growth plates located?

You have growth plates in most bones that are longer than they are wide. The main ones are in:

• The thighbone (femur), near the hip and just above the knee
• The lower leg (tibia and fibula), just below the knee and above the ankle
• The forearm (radius and ulna), near the elbow and the wrist
• The hands and fingers, and the feet and toes

You can't see or feel them from the outside. On an X-ray they show up as dark lines near the ends of the bones, because cartilage holds less mineral than bone. Your height comes mostly from the bones of your legs and your spine, which both lengthen a lot during the growth spurt.

How growth plates make you taller

Inside the plate, cartilage cells keep multiplying and lining up in columns. On the side facing the shaft, the oldest cartilage is gradually turned into bone. The plate itself stays thin, but the bone behind it keeps getting longer.

Puberty hormones first speed this process up, which is the growth spurt, and then shut it down. The hormone that finally closes growth plates is estrogen, in boys as well as girls (boys make it from testosterone). Strong evidence came from a 28-year-old man whose body could not respond to estrogen: his growth plates were still open, he had kept growing into adulthood, and he stood about 6'8" (204 cm).

When do growth plates close?

Growth plates close gradually. On X-rays they get thinner and then disappear as the cartilage is replaced by bone. The timing follows puberty, not birthdays, so it varies by several years from one person to another.

Growth plate closing age for females

Girls usually start puberty between 8 and 13 and have their growth spurt between about 10 and 14. Height gain peaks before the first period, which comes at 12.5 on average. After periods begin, most girls grow only about 1 to 2 more inches and reach adult height around 14 or 15. More detail is in our guide on when girls stop growing.

Growth plate closing age for males

Boys start puberty later, and their growth spurt comes about two years after girls'. Boys grow fastest between about 12 and 15, and most have stopped or nearly stopped growing by about 16. Late bloomers are the exception: if puberty starts late, the growth plates stay open longer and growth continues later. On CDC charts, median height for boys still rises about 0.6 in (1.6 cm) between ages 17 and 20. See when boys stop growing and our late bloomer guide.

What happens when growth plates close?

When the last of the cartilage turns to bone, the plate is "closed" (or fused). The bone can still get thicker and stronger, but it can no longer get longer. Once the plates in your legs and spine have closed, your height is set.

This is why no stretching routine, supplement or hormone can add real height to an adult, and why claims about "reopening" growth plates don't hold up. We explain the science in can you keep growth plates open?

How do you know if your growth plates are closed?

There is no reliable home test. Signs like height that hasn't changed in a year or a fully adult-looking body are only hints. The only precise answer is an X-ray, usually a bone-age X-ray of the left hand and wrist that a doctor compares with standard reference images. Our step-by-step guide covers how to tell if your growth plates are closed.

Growth plate injuries

Because they are softer than bone, growth plates break more easily. The Children's Hospital of Philadelphia estimates that growth plate injuries make up as many as one in three childhood fractures. They happen about twice as often in boys, partly because boys' plates stay open longer. The most common spots are the fingers, the forearm near the wrist, and the lower leg.

Injuries come from a single accident (a fall, a hard tackle, a bike crash) or from repeating the same movement over and over in sports. Overuse problems that involve growth plates include Osgood-Schlatter disease (knee), Sever's disease (heel) and Little League elbow or shoulder.

Signs of a possible growth plate injury:

• Pain and tenderness that don't go away after an injury or hard training
• Swelling or warmth near the end of a bone, close to a joint
• A limb that looks bent or a joint that won't move normally
• Not being able to put weight on a leg, or a lasting limp

Most growth plate fractures heal without lasting effects. Rarely, a bony bridge forms across the injured plate, and the bone can end up shorter or slightly crooked. That is why doctors usually follow these injuries for at least a year.

When to see a doctor

See a doctor promptly after any injury near a joint that causes lasting pain, swelling, a visible deformity or trouble bearing weight. For growth itself, book a checkup if:

• Your growth has slowed down or stopped earlier than friends of the same age
• You have dropped from one percentile line to a lower one on the growth chart
• A boy shows no signs of puberty by about 14, or a girl by about 13
• You are much shorter than your parents' heights would suggest

The doctor may order a bone-age X-ray to see how open your growth plates are and how much growing time is left.

The takeaway

Growth plates are where your bones get longer, and they close at the end of puberty, usually by 15 in girls and 17 in boys, sometimes later in late bloomers. While they are open, sleep, good nutrition and staying active help you reach your full potential. To see where you stand now, try the Am I Done Growing? quiz or estimate your adult height with the height calculator.