Canadian researchers have found a link between the looseness of a woman's knee joint and her monthly hormone cycle. Investigators monitored 26 women throughout the course of their monthly menstrual cycle. Their knee looseness--or laxity--was measured at each phase of the cycle, and they were asked to perform several athletic movements. The researchers found that greater knee looseness lead to differences in the joint's movement  that could lead to injury if the woman were doing intense...