[superchao]

Osteoporosis is when bones become brittle and weak.
The bones are joined together by tendants. Within the tendant area is a
tissue called cartilage. The cartilage reduces friction when moving bones,
so that the bones dont wear down and become shorter and weaker.
Usually, sports like football, soccer, and sometimes basketball
can give injuries where the player rips some cartilage, leaving an
open area for bones to grind on each other, and the bones also become loose.