Adults do not have active growth plates. The cartilage plates that allow bones to lengthen during childhood and adolescence gradually harden into solid bone, a process that finishes for most people by their early twenties. Once that happens, the plates are permanently gone, and bones can no longer grow longer.
What Growth Plates Are and Why They Disappear
Growth plates (technically called epiphyseal plates) are bands of cartilage near the ends of long bones like the thighbone, shinbone, and forearm bones. During childhood, cartilage cells in these plates multiply and push outward, while older cells on the inner edge die off and get replaced by hard bone. This conveyor-belt process is what makes bones, and you, taller.
The process can’t continue forever. The cartilage cells have a finite capacity to divide. Once that capacity is used up and the proliferation rate drops to essentially zero, the remaining cartilage rapidly converts to bone. What’s left is a thin line of denser bone called the epiphyseal line, a faint scar visible on X-rays that marks where the plate used to be. That line is permanent but inactive. It plays no role in further growth.
When Growth Plates Close
Growth plates don’t all close at once. They follow a predictable sequence, and the timeline differs between males and females. In females, at least half have fused growth plates at major bone sites between ages 14 and 17, with 90% reaching full fusion between 15 and 18. All females in one large MRI study had closed plates at every measured site by age 19.
In males, the 50% mark falls between ages 15 and 18, the 90% mark between 17 and 20, and complete closure at all sites occurred by age 21. Girls finish roughly two years ahead of boys across all bones studied.
The bones themselves close in a consistent order. The heel bone tends to fuse first, followed by the lower and upper shinbone, then the lower thighbone. The wrist end of the forearm bone (the distal radius) is typically the last of the major long bones to close, finishing around age 16.5 in girls and 17.5 in boys. One bone lags even further behind: the inner end of the collarbone is the very last growth plate in the entire skeleton to fuse, sometimes showing incomplete fusion into the mid-twenties. Fusion marks at that site can remain visible on imaging until around age 30.
Why Estrogen Controls the Timing
Estrogen is the primary hormone responsible for shutting growth plates down, in both men and women. This is why puberty and growth plate closure are so closely linked. As estrogen levels rise during puberty, the cartilage cells in the growth plate age faster. They burn through their remaining divisions more quickly, reaching exhaustion sooner. Once they stop dividing, fusion happens rapidly.
This relationship explains several things. Girls, who experience a larger and earlier rise in estrogen, close their plates sooner and tend to stop growing at a younger age. In rare cases where the body can’t produce or respond to estrogen, growth plates fail to fuse entirely, and the person keeps growing well into adulthood. The opposite also holds: children who enter puberty unusually early (precocious puberty) experience a burst of fast growth followed by premature plate closure. They may be tall for their age as children but end up shorter as adults because their bones sealed off too soon. Treatments that suppress early puberty can restore more normal adult height by preserving growth plate activity longer.
What Happens to Adult Bones Without Growth Plates
Once growth plates are gone, your bones are locked at their current length. But bones are living tissue, and they continue to remodel throughout life. They can get thicker or thinner, denser or more porous, depending on factors like exercise, nutrition, and hormones. What they cannot do is get longer.
This distinction matters in conditions like acromegaly, where the body produces too much growth hormone after the plates have already closed. In a child with open growth plates, excess growth hormone leads to extreme height (gigantism). In an adult, the same hormonal excess can’t add height. Instead, it causes certain bones to widen and thicken. Hands and feet enlarge, the jaw and brow become more prominent, the nose broadens, and gaps can develop between teeth. The ribs may also expand, changing the shape of the chest. These changes happen because adult bone can still grow in width through surface deposition, even though lengthwise growth is no longer possible.
How Doctors Check Growth Plate Status
A simple X-ray of the left hand and wrist is the standard way to determine whether growth plates are still open. Active growth plates show up as darker bands near the ends of bones because the cartilage is softer and contains fewer minerals than surrounding bone. As a child matures, these bands thin out on successive X-rays. When they vanish completely, the plates are closed and growth in height is finished.
This imaging is commonly done as a “bone age study” in children to assess whether skeletal development is on track relative to their chronological age. In young adults, it can confirm whether any growth potential remains. For the collarbone specifically, CT scans provide a more detailed view and are sometimes used in forensic age estimation, since that bone’s fusion timeline extends later than any other.
Can Adults Gain Height Without Growth Plates?
Because closed growth plates cannot reopen or regenerate, no supplement, exercise, or hormone therapy can restart natural bone lengthening in adults. Growth hormone supplementation in adults with normal, fused plates does not increase height.
The one exception is surgical. A procedure called distraction osteogenesis involves deliberately cutting a bone (usually the shinbone or thighbone), then slowly pulling the two halves apart using an external frame or an internal device implanted inside the bone. The body fills the widening gap with new bone tissue, typically at a rate of about 1 millimeter per day. This allows adults to gain several centimeters of height, but it’s a lengthy process involving months of gradual stretching followed by additional months of healing. It works by exploiting the body’s fracture repair system rather than reactivating growth plate biology.