The important interaction between mobility disorders and falls is further highlighted by epidemiologic case–control studies conducted to identify risk factors that increase the likelihood of falling. Taken together, these studies indicate that lower extremity weakness, gait and balance disorders, previous falls, functional impairment, visual deficits, cognitive impairment, depression, and polypharmacy (defined as taking ≥ 5 prescription medications) are the most important risk factors for falls. For example, data summarized from 17 studies suggest that persons with readily identifiable leg weakness have a four- to fivefold increase in risk for falls, and persons with impaired gait or balance have approximately a threefold increase (1). Seven additional studies have identified specific risk factors for injurious falls (1, 7). In general, these risk factors are the same as those for noninjurious falls, with the addition of factors associated with osteoporosis (for example, being female, having decreased bone density, and being underweight) and the use of physical restraints. Perhaps as important as identifying individual risk factors is appreciating the interaction and probable synergism among several risk factors. Several studies have shown that the risk for falling increases dramatically as the number of risk factors increases. For example, three separate studies have reported that 65% to 100% of elderly persons with three or more risk factors fell in a 12-month observation period, compared with 8% to 12% of persons with no risk factors (1, 7–9).