How are the bone age tests interpreted?

Last updated on May 15, 2022


You said sometimes you can ejaculate in stage 3 a while back during one of the “pauses”. What do you mean by pauses? Do you mean pauses in growing before hitting your growth spurt?

When do boys start getting acne? Does it normally happen near 3.5 or when you enter stage 3 so 3.0?

I read on a website about bone age that the growth spurt happens on average at 14.2 years in terms of bone age. So a bone age of 14.2 on average is the time of a growth spurt. However, another website says that boys’ PHV is on average at 13.5 years. How are the bone age test results interpreted? Does it mean the lower your bone age the more you have left to grow? Let’s say a guy gets a bone age of 14. How many inches would they have left to grow?

A pediatrician I had years ago asked me to bend down so they could inspect me, I guess. I think I was like 11 or maybe even younger. I don’t remember what exactly she said, but I think she told my dad that I will grow a lot in the 8th grade. I think she said 8th grade I am not sure. It could be 9th or maybe 10th. I will turn 14 before I start 9th grade. How did she just assume this by just having me bend down? I think she was looking at my back. It had nothing to do with her checking my puberty stage, a bone age test, or genetically predicting stuff. I am curious how she came up with that.


Growth in height is not constant. There is only so much energy available to fuel growth and your organs have to also grow to support your new size. So your bones may grow for a while, pause while your organs grow, and then your bones grow again. It is possible that during one of these pauses in bone growth your reproductive organs grow enough to support ejaculating semen. However, most boys usually start ejaculating before growth (stage 2) or when growth slows down (stage 4).

Acne begins to show up during stage 3 but gets worse during stage 4. I really can’t get more precise than that. However, if a boy is having acne, then he is likely getting close to stage 4.

The bone age test compares the maturity of the bones in your hand against a standard that represents the average boy at a particular age. In theory, if your bone age matches your actual age, then you are developing at the same rate as the average boy. See What is the difference between bone age and a Tanner Stage? for a detailed description. The lower your bone age, the less you have developed so far. Peak Height Velocity (growth spurt) begins when a person reaches 90% of their final height [James O. Sanders, “The Uniform Pattern of Growth and Skeletal Maturation during the Human Adolescent Growth Spurt,” Scientific Reports, 2017, 7: 16705.] Peak Height Velocity for the average boy is just before they turn 14, but the range is one year, so anywhere from just before 13 to just before 15. In other words, these tests are not as precise as you might hope.

Your pediatrician had you bend forward to check the bone structure in your upper body. The doctor was looking for things like curvature in your spine, asymmetry in your bone structure, or differences in the lengths of your limbs. See Adam’s Forward Bend Test. My guess is that she had made a determination as to what stage in development you were at earlier. She just didn’t start talking about them with your father until after she completed all the tests.


Wait! So in theory, if someone had a lower bone age than another kid, the kid with the lower bone age would grow more in height, right?

Also, what is the difference between pimples and acne?


14-year-old boys at different stages of development

I think you misunderstand what is meant by bone age. In the pictures to the right, the three boys are all the same physical age of 14. However, they are clearly at different stages of physical development. The boy to the left might have a bone age of 12; that is, his body is developed like that of the average 12-year-old boy. The boy in the center might have a bone age of 13.5 and the boy at the left might have a bone age of 15.

Therefore, a boy with a lower bone age is also more likely to be shorter than a boy with a higher bone age, at that moment in time, simply because he hasn’t reached his growth spurt yet. A person’s bone age will not tell you what their final height will be. It only indicates how developed they are compared to the average boy.

Pimples and acne are synonyms. There is no difference.


Wait, so two kids are both 14. One of them has a bone age of 12. The other has a bone age of 14. The 12-year-old bone age kid is not going to necessarily be taller than the 14-year-old bone age kid, but he is going to grow more because his bones aren’t as developed.

Is it possible to be in a high tanner stage, but your bones aren’t as developed and you have a lot of growing left to do with a low bone age?

When you say “how developed,” do you mean in terms of puberty like Tanner stages of (pubic area, testicles, armpit hair, etc.) or in terms of bone development and more inches left to grow?


There are multiple sequences of changes that take place that in sum mean you have changed from a child to an adult. The sequences each go roughly together. Thus, people have been using the sequences that can be seen (pubic hair, genital development, etc.) to estimate what can’t be seen. The bone age test uses x-rays of your hand and wrist bones to estimate what is going on with the rest of your bones. While these sequences are roughly connected, they are not far out of sync with each other. Thus, high bone age and high Tanner stage go together. If they didn’t, the estimates would be worthless.

Your changes (how developed you are) are not just about height. There are many factors that make an adult different from a child. I am talking about the whole.