How Can You Tell If Your Growth Plates Are Still Open?

The only definitive way to tell if your growth plates are still open is medical imaging, most commonly an X-ray of the left hand and wrist. A doctor compares the image against a standardized atlas to estimate your skeletal maturity, and the appearance of the growth plates on that image reveals whether they are active, partially fused, or fully closed. Physical clues like still gaining height or being in mid-puberty can suggest your plates remain open, but they are indirect and imprecise. The imaging approach is straightforward, widely available, and has been the clinical standard for decades.

What Growth Plates Are and Why They Eventually Disappear

Growth plates, also called physes, are thin layers of cartilage near the ends of long bones. They are the engine behind your bones getting longer during childhood and adolescence. Within each plate, cartilage cells go through a structured life cycle: they rest, they multiply, they enlarge, and then they die off and are replaced by hard bone tissue.¹ This process repeats continuously throughout the growing years, and every round of it adds a small amount of length to the bone.

Growth plates close when that cartilage cell supply runs out. As you approach the end of puberty, the reserve of progenitor cells in the “resting zone” of the plate dwindles. Fewer cells multiply, and the ones that do produce smaller columns of new cartilage. Eventually, the remaining cartilage is replaced entirely by bone, the gap between the bone shaft and the bone end fills in, and the plate is gone for good.² Once that happens, the bone can no longer grow longer. This is why adults do not keep getting taller.

The Standard Test: A Hand and Wrist X-Ray

If your doctor wants to know whether your growth plates are still open, they will almost certainly order an X-ray of your left hand and wrist. The hand has dozens of small bones that mature in a predictable sequence, making it an efficient single snapshot of skeletal development. The most widely used reference is the Greulich-Pyle (GP) atlas, which catalogs what the hand and wrist look like at each stage of maturation. In the GP system, the maximum recorded skeletal age is 18 years for females and 19 years for males; once the bones match those final reference images, the growth plates are considered closed.³

The procedure is quick and low-radiation. A single X-ray of the hand exposes you to a tiny dose, roughly comparable to a few hours of natural background radiation. The radiologist or endocrinologist then eyeballs the film and compares it, bone by bone, to the atlas images. This comparison yields a “bone age,” which may be ahead of, behind, or in line with your actual calendar age. If your bone age is well below the GP maximum for your sex, your plates are still open and you likely have growing left to do. If bone age matches the adult reference, growth is finished.

One limitation worth knowing: the GP atlas was originally developed using X-rays from mid-twentieth-century American children, and skeletal maturation can vary across populations. Studies have tested its reliability in different groups and generally find it useful, though small systematic biases can show up.⁴ For clinical purposes, those biases rarely change the big-picture answer of whether your plates are open or closed.

MRI and Ultrasound as Alternatives

X-rays work well, but they involve a small dose of ionizing radiation. For situations where repeated imaging is needed, or when radiation is a concern, MRI offers a radiation-free alternative. A large cross-sectional MRI study of nearly a thousand healthy adolescents and young adults examined the wrist, knee, and ankle and confirmed that growth plate fusion can be reliably assessed with MRI.⁵ MRI is also the preferred method in forensic age estimation, where ethical standards increasingly demand non-ionizing techniques.⁶

Ultrasound is a newer and more portable option. A study of male adolescents found that ultrasound of the knee could identify open growth plates with perfect sensitivity, catching every case where the plates had not yet fused, and with reasonably high agreement between different examiners.⁷ Ultrasound is cheaper and more accessible than MRI, though it is not yet as widely adopted in clinical practice for bone age assessment. Still, the fact that it works opens the door for quicker, bedside-type checks in the future.

Physical Clues That Suggest Your Plates Are Still Open

Not everyone needs an X-ray to get a rough sense of whether they are still growing. Several physical signs serve as indirect evidence.

The most obvious is height gain itself. If you have been reliably measured over the past year and are still getting taller, your growth plates are still active somewhere. The tricky part is that growth can slow dramatically in late puberty, dropping to under a centimeter per year, which is hard to detect without careful measurement at regular intervals. Peak height velocity, the fastest rate of growth during the adolescent spurt, happens at different times and at different pubertal stages for different people.⁸ So the fact that your growth has slowed doesn’t tell you exactly where you are in the process.

Pubertal stage is another clue. In girls, growth typically slows substantially after menstruation begins and usually finishes within two to three years of the first period. In boys, the growth spurt tends to peak a couple of years after puberty’s earliest visible signs and slows as the voice deepens and facial hair becomes established. These are rough guides, not precise ones. The substantial variability in the timing of peak height velocity across pubertal stages means that two kids at the same Tanner stage can be in very different places in their growth trajectory.

Shoe size stabilizing is another informal marker people notice. Feet tend to reach adult size before height does, because the growth plates in the foot fuse earlier than those elsewhere. That same MRI study of adolescents found that growth plate fusion proceeds in an ascending order, from the foot up to the wrist.⁵ So stable shoe size does not mean you are done growing taller; it just means your feet are done.

The General Timeline for Closure

Growth plates do not all close at the same time. The timeline depends on which bone you are looking at and whether you are male or female. Most of the growth plates in the long bones of the arms and legs fuse during mid-to-late puberty. In girls, the majority are closed by around age 14 to 16. In boys, closure tends to happen between about 16 and 18. These are averages, and variation of a year or two in either direction is normal.

The hand and wrist, being the standard site for assessment, finish maturing at the upper end of that range: roughly 18 in females and 19 in males by GP atlas standards. The knee’s growth plates, which contribute a large share of leg length, close around a similar window. But if you zoom out to the entire skeleton, the picture is more complex.

The very last growth plate in the body to close is the one at the inner end of the collarbone. The medial clavicular epiphysis does not fuse until the early to mid-twenties, much later than any other growth plate. Research shows that complete fusion of the clavicle was first observed at age 22 and was present in everyone by age 27.⁹ Another study found that the clavicle continues meaningful growth during adolescence and into early adulthood, with its growth plate not fusing until 23 to 25 years of age.¹⁰ This is worth knowing for a few reasons: it means that clavicle imaging is sometimes used to estimate age in young adults, and it means that the skeleton is technically not “done” at 18, even if your height has been stable for years.

Why Estrogen Is the Real Gatekeeper

People often assume testosterone is what drives growth plates to close, since boys tend to close later and grow taller. The reality is that estrogen is the primary hormone responsible for fusion in both sexes. This was demonstrated clearly in research showing that estrogen accelerates the senescence of growth plate cartilage cells, pushing them toward exhaustion and triggering the replacement of the remaining cartilage by bone. Fusion happens when the rate of cartilage cell multiplication drops to zero, and estrogen speeds up the countdown to that point.¹¹

Boys close later not because they lack estrogen, but because they produce less of it during early and mid-puberty relative to girls. Boys convert some of their testosterone to estrogen via an enzyme called aromatase, so eventually their estrogen levels rise enough to trigger closure, just on a delayed schedule. Girls, whose estrogen levels rise sharply earlier in puberty, reach that fusion threshold sooner. This is also why conditions that disrupt estrogen signaling can lead to unusual growth patterns. Rare cases of estrogen receptor deficiency or aromatase deficiency in men have resulted in growth plates that failed to fuse even into the late twenties, producing unusually tall stature.¹²

Growth hormone and its downstream mediator, IGF-1, play a separate role. They stimulate the cartilage cells to divide and enlarge, driving actual growth. IGF-1 promotes growth at every stage of cartilage cell development within the plate.¹³ So growth hormone makes the plates produce bone faster, while estrogen determines when they stop. The interplay between the two is why children with growth hormone deficiency are short but still eventually close their plates, and why children with precocious puberty grow fast at first but end up shorter as adults.

When Growth Plates Close Too Early or Too Late

Precocious puberty, defined as puberty beginning before age 8 in girls or age 9 in boys, causes early exposure to sex hormones and accelerates bone maturation. These children shoot up in height initially but their growth plates fuse earlier than expected, often resulting in shorter adult stature than they would have otherwise reached.¹⁴ This is one of the main clinical reasons doctors check bone age in children who show early pubertal signs. If the bone age is significantly advanced, treatment with gonadotropin-releasing hormone agonists can slow the process and preserve more growing time.

Physical injury to the growth plate is a different kind of disruption. Fractures that cross the growth plate, classified as Salter-Harris fractures, can damage the cartilage cell layer and lead to a bony bridge forming prematurely across the plate.¹⁵ When that happens, the affected part of the bone stops growing while the rest continues, which can cause the limb to grow crooked or shorter than the other side.¹⁶ This is why any fracture near a joint in a growing child gets careful follow-up.

On the other end, delayed puberty or certain medical conditions can keep growth plates open longer than expected. Constitutional delay of growth and puberty is the most common reason and is usually benign. These kids are “late bloomers” who end up reaching a normal adult height, just on a slower schedule. More rarely, deficiencies in estrogen production or signaling keep plates open well past the typical age of closure, as mentioned earlier.

What Bone Age Can and Cannot Tell You About Final Height

One of the most common reasons people ask about growth plates is that they want to predict their final adult height. Bone age assessment is the foundation of most height prediction methods. The basic logic is straightforward: if you know how skeletally mature someone is and how tall they are right now, you can estimate how much growing they have left.

The most widely used prediction algorithm, the Bayley-Pinneau method, has been around for decades and is still applied in over 40 published studies.¹⁷ Newer approaches use artificial intelligence to read the X-ray and predict both bone age and final height. A deep-learning-based system predicted final adult height with an average error of roughly 4 to 5 centimeters compared to the actual adult height. Experienced human raters did better, averaging around 3 centimeters of error. Modern automated systems in healthy populations can get errors down to about 2 to 3 centimeters.¹⁷

The catch is that accuracy drops in certain clinical situations. In children with growth hormone deficiency, initial predictions tend to underestimate final height by 4 to 8 centimeters, and that shifts to overestimation of 2 to 4 centimeters after treatment begins. In constitutional delay of puberty, predictions tend to overestimate by 1 to 5 centimeters. Integrative models that fold in parental height and pubertal staging alongside bone age imaging perform better overall. So bone age is a useful piece of the puzzle, but it is not a crystal ball, especially in kids being treated for growth-related conditions.

Can You Delay Closure to Grow Taller?

Because estrogen drives fusion, blocking estrogen’s effects can theoretically keep growth plates open longer. Aromatase inhibitors, which prevent the conversion of testosterone to estrogen, have been studied for exactly this purpose. They appear to slow the process of growth plate fusion and have been explored as a way to increase adult height in boys with short stature and delayed puberty.¹⁸

In a controlled trial, boys treated with the aromatase inhibitor letrozole showed significantly slower bone maturation than those given a placebo. Over 18 months, bone age advanced only about 0.9 years in the letrozole group versus 1.7 years in the placebo group, and predicted adult height increased by about 5 centimeters in the treatment group.¹⁹ These results are promising but come with important caveats. Aromatase inhibitors are not approved for this use in most countries, long-term safety data in growing adolescents remains limited, and blocking estrogen can affect bone density and other systems. This is firmly in the territory of specialist endocrinology, not something to try on your own.

Factors That Influence How Quickly Plates Close

Sex and pubertal development are by far the strongest predictors of when growth plates fuse. But several other factors play a role. Body mass index appears to be one. The large MRI study mentioned earlier found that BMI significantly influenced the timing of growth plate fusion, while physical activity did not.⁵ Higher body fat is associated with higher estrogen levels in both sexes, which may explain why kids with higher BMI tend to mature skeletally a bit faster. Conversely, very lean or malnourished children may experience delayed maturation.

Environmental chemicals are also drawing research attention. Endocrine-disrupting compounds, found in plastics, food packaging, and personal care products, can mimic or interfere with hormones. A study of children’s exposure to several of these compounds found mixed effects on bone maturation: some chemicals were associated with advanced bone age in prepubertal girls, while others were associated with delayed maturation, depending on the specific compound, BMI, and pubertal stage.²⁰ The picture is complex and far from settled. No one is going to tell you that a specific household product will close your growth plates early. But the broader finding that low-level chemical exposures can nudge skeletal timing in either direction is one researchers are taking seriously.

Nutrition gets a lot of speculation online but has less clear-cut evidence than people expect. A study of 12- to 13-year-old girls found that adherence to a healthy dietary pattern correlated with bone age being closer to (or slightly advanced relative to) calendar age, but the effect size was small.²¹ Severe malnutrition clearly delays skeletal maturation, but once you are reasonably well-nourished, the evidence for specific foods accelerating or delaying closure is thin.

Forensic Uses of Growth Plate Assessment

Outside of pediatric clinics, growth plate status is examined for a very different reason: estimating the age of individuals who lack reliable documentation. This comes up in immigration proceedings, criminal cases involving minors, and disaster victim identification. The stakes can be high — whether someone is classified as a minor or an adult often depends on the legal threshold of 18, and growth plate fusion is one of the main biological markers used to make that call.

MRI of the wrist, specifically the distal radius, has been evaluated for distinguishing people above and below legal age thresholds of 15 and 18. The staging method applied to wrist MRI appears applicable for this purpose in both sexes.²² Knee imaging is also used, with the fusion patterns of the distal femur and proximal tibia providing additional data points.²³ The clavicle, because its growth plate fuses so late, is particularly useful for distinguishing 18-year-olds from people in their early twenties, a distinction that other skeletal sites cannot make reliably.²⁴

The move toward MRI rather than X-ray in forensic settings reflects growing ethical concerns. Exposing someone to ionizing radiation purely for legal purposes, especially when their age is the very thing in question, raises different ethical considerations than doing so for medical diagnosis. MRI avoids that problem entirely, which is why forensic age estimation protocols in Europe increasingly rely on it.

Growth Plates in Other Species

Humans are not the only animals with growth plates, but we are unusual in the timing. A review comparing growth plate closure across laboratory animals and humans found that the ratio of age at growth plate closure to lifespan varied widely. Rats, for instance, continue growing for a larger fraction of their lifespan than most other species, with their growth plates remaining open far longer after sexual maturity than is typical.²⁵ Mice, which are the workhorse of growth plate research, actually never fully close their growth plates the way humans do; they simply slow bone elongation to a crawl.¹² This matters because a lot of what we know about how estrogen and growth hormone affect the growth plate comes from rodent studies, and the translation to humans is not always straightforward. Findings from mice about keeping growth plates open or accelerating closure need to be interpreted carefully before drawing conclusions about human treatment.