骨龄是一种用以描述青少年骨骼发育程度的数据。在人类的生长期内，从婴幼儿到成年人，骨骼的形态、大小都会有所变化。而这种变化可以通过X射线检查到。骨龄的相关数据是根据同年龄段、同种族儿童的平均数据综合而成。结合儿童目前的身高及骨龄可以预测出他未来的身高数据。对于大多数人来说，骨龄和生物年龄是一样的。而对于一些人来说，他们的骨龄和生物年龄会有几年的差距，或年轻或年长。那些骨龄长于生物年龄的通常发育偏早，但是停止生长的时间也偏早。骨龄年轻于生物年龄的正好相反。那些身高低于平均水平的孩童并不一定是骨龄年轻于生物年龄。事实上，如果不加治疗，他们的骨龄可能年长于实际生物年龄，从而阻碍他们的生长。

Bone age is the degree of maturation of a child's bones. As a person grows from fetal life through childhood, puberty, and finishes growth as a young adult, the bones of the skeleton change in size and shape. These changes can be seen by x-ray. The "bone age" of a child is the average age at which children reach this stage of bone maturation. A child's current height and bone age can be used to predict adult height. For most people, their bone age is the same as their biological age but for some individuals, their bone age is a couple years older or younger. Those with advanced bone ages typically hit a growth spurt early on but stop growing early sooner while those with delayed bone ages hit their growth spurt later than normal. Kids who are below average height do not necessarily have a delayed bone age; in fact their bone age could actually be advanced which if left untreated, will stunt their growth.