Girl is playing a friendly game of arm wrestle. When it is least expected, her arm snaps in half. She freaks out omg omg my arm is broken omg.

Bone health is something we often neglect, mostly because our bones seem to be capable of taking care of themselves...
The bones contain OSTEOPHYTES, which are the cells that make up the bone, OSTEOBLASTS, which are precursors to the Osteophytes and grow to become them, and OSTEOCLASTS, which break down and remove old bone cells.
The presence of testosterone makes bone density more (making males naturally stronger that females, averagely).
But other factors contribute to bone strength, apart from testosterone.
The bones that bear the most weight (like bones in the legs) tend to be stronger than those that don't.
People who consume more calcium in their diet (like diets rich in dairy products) and those who are exposed regularly to Early morning sunlight, stand a better chance of having stronger bones.
Those who also engage more in physical activity, including weight bearing exercised tend to have stronger bones too...