On an x-ray, growth plates look like dark lines at the ends of the bones. At the end of growth, when the cartilage completely hardens into bone, the dark line will no longer be visible on an x-ray. At that point growth plates are considered closed.
You wouldn't know for sure unless you looked at an X-ray of the legs. That said, hand and wrist X-rays are a standard use as a predictor of skeletal maturity in children, so it may be that your son has finished growing. The growth plates in the knees generally close at about the same time as the ones in the wrist.
Children's bones have areas of new bone growth called growth plates at both ends. They add length and width to the bone. They can be seen on an X-ray because they're softer and contain less mineral, making them appear darker on an X-ray image than the rest of the bone.
As a child grows, the shafts get longer, and bone gradually replaces the cartilage epiphyses. Through the growing years, a layer of cartilage (the growth plate) separates each epiphyses from the bone shaft. Between 17 and 25 years, normal growth stops. The development and union of separate bone parts is complete.
As mentioned in one of the articles one good way to see if you still have growth potential is to X-ray a wrist- the test is called a Pediatric Bone Age. It will show if your growth plates are still open. A doctor can also request lab tests- checking for hormones- such as thyroid, growth hormone and sex hormones.
When Do Growth Plates Close? Growth plates usually close near the end of puberty. For girls, this usually is when they're 13–15; for boys, it's when they're 15–17.
Increasing your height after 18 is not possible, even through nutrition and exercise, because the growth plates stop growing. The growth plates (epiphyseal plates) are present at the end of long bones.
Pediatric orthopedic surgeons can estimate when growth will be completed by determining a child's “bone age.” They do this by taking an x-ray of the left hand and wrist to see which growth plates are still open. The bone age may be different from the child's actual age.
During the terminal phase of differentiation, cartilage is replaced by blood vessels and organized bone tissue, and once chondrocytes have died, the longitudinal growth of the bone ceases and the growth plate closes.
On average, females stop growing around age 13 to 15, and boys around age 15 to 17. Obviously many children continue to gain some height into their late teen years, but the vast majority of growth is over by these ages.
Growth plates are areas of cartilage at the ends of bones that are key to a child's ability to grow. Once a growth plate hardens into solid bone it closes forever – meaning the child's growth is complete. Typically, that happens around age 14 for girls and age 16 for boys, although it can vary widely.
Although some men may continue to grow in their 20s, most men's growth plates are closed by 21 years. Hence, it is unlikely for men to grow after 21 years, with some exceptions. In a healthy growth pattern, your bone increases in length due to the growth plates in the bone called epiphyses.
Changes in Boys
They tend to grow most quickly between ages 12 and 15. The growth spurt of boys is, on average, about 2 years later than that of girls. By age 16, most boys have stopped growing, but their muscles will continue to develop.
The expected average height of a healthy population should be 163 cm for women and 176.5 cm for men – as defined by the WHO growth reference standards. Interestingly, the global average height is 159.5 cm for women, and 171 cm for men – it's lower than we'd expect.
Is the height of 174 cm considered average or tall for Indian men? Without going into statistics, 174 or 5′ 8″ will fall into the upper end of the average band. Today a 5′9″ man can possibly be considered tall, but that is starting point of the band.
Does skipping increase height? No! it is a myth and cannot happen when you practice it as an adult. The ossified and epiphyseal plates would have been sealed by the age of 18, and therefore rope skipping after 18 cannot make you taller.
“Stretching does not make you taller, but it can help in improving flexibility and posture, which can make someone seem taller,” Hashish said. “For instance, if someone slouches, they may appear shorter than when they stand upright with more extension.”
The growth plates fuse in an ascending order, from the foot to the wrist, and females mature significantly earlier than males.
After the growth plates fuse, there is no more increase in height, and we all then shrink gradually as we get older. Normal growth is controlled by a number of hormones: Growth hormone, made in the pituitary gland, which is the most important factor.