Women and men have different outcomes from a fall. For instances, women fall differently than men and absorb mechanical energy at different parts of the body (e.g. hip). Men tend to sustain more brain injury than women.

Single risk factor ( e.g. the relationship of falls and medication) and multiple risk factors, synergic effects of factors are investigated in several prospective studies, and retrospective studies. The physiologic changes of aging such as slower reflexes, increased postural sway, and declined visual ability, contribute to instability prone to fall. Weak muscle strength and balance, gait reaction time as well as decreased skeletal strength had been consistently implicated in falls in the elderly(Tinetti, 1988; Nevitt, 1989). Lower leg strength, particularly at hip and anterior tibia, is correlated with balance and risk of falling (Gehlsen, 1990).