How old is bone age when menstruation starts?

Generally, girls start menstruating when their bone age is between 12 and 16 years. Some girls who develop earlier may have their first menstrual period around 9 to 10 years of age, which corresponds to a condition where bone age exceeds chronological age. These girls usually enter puberty earlier and show early development of secondary sexual characteristics such as breast development. Clinically, bone age assessment is commonly used to help diagnose precocious puberty in girls. Precocious puberty refers to the development of secondary sexual characteristics before the age of eight or the onset of menstruation before the age of ten.

Bone age primarily refers to the skeletal maturity and can help determine the stage of puberty and assess potential for height growth. In most individuals, bone age closely matches chronological age. Since girls typically begin menstruating between the ages of 12 and 16, their bone age at menarche is approximately 12 to 16 years.

The onset of menstruation marks a girl's entry into puberty. At this stage, the ovaries begin secreting sex hormones, growth in height accelerates, and symptoms such as breast tenderness may occur. As the post-menarche phase is still part of the growth period, bone age evaluation can be used together with other assessments to monitor physical development. After menstruation begins, maintaining balanced nutrition, sufficient sleep, and moderate exercise can support continued height growth.