Know the meaning, uses, and limitations of bone age
I find it fascinating how bone show our age, nutritional status, and fitness. When we're young, a lot of your skeleton is not made of bone yet, it's made of cartilage, which grows and then is replaced by bone. Based on x-rays, usually of the wrist and hand (convenience), the radiologist can either compare your bones with standard, healthy, films of bones of various ages, or use a complex formula to do the same thing. This is usually done when a young person isn't growing as expected, and we're looking into the cause. As we age, films show us bone density, which is a complex result of heredity, nutrition, and exercise. At any point in life, though, if you are nutritionally in trouble with your calcium and phosphorous, your bones are less dense, and this can be seen radiographically.
What are some drawbacks. Firstly, radiation. Secondly, if a radiologist is in a hurry and just glances at your films and the control films, the estimate of your bone age can be off by quite a bit, so you want a methodical person who's done this before to read your films. Lastly, the controls were white with good socioeconomic standing. Genetically, some of us may age more quickly or slowly and still be "normal", so this is a matter that still needs looking into.
Reference: Willenborg, A. Bone Age. Pediatrics in Review (1993) vol. 14 (4) pp. 133