This article systematically reviewed the epidemiology studies on sports injury which ankle injury was included. The time span started from 1977 to 2005. A total of 227 studies reporting injury pattern in 70 sports from 38 countries were included. The total included cases were 201600 with 32509 (16%) ankle injuries. A total of 11847 (84%) ankle sprains were recorded from 14098 cases with available ankle injury information. Results show that the ankle was the most common injured body site in 24 of the 70 included sports, especially in aeroball, wall climbing, indoor volleyball, mountaineering, netball, and field events in track and field. Ankle sprain was the major ankle injury in 33 of the 43 sports, especially in Australian football, field hockey, handball, orienteering, scooter and squash. In general sports injury among countries, the ankle was the second most common injured body site after the knee, and ankle sprain was the most common type of ankle injury. The incidence of ankle injury and ankle sprain was high in court game and team sports, such as rugby, soccer, volleyball, handball, basketball, field hockey, dancing, American football, netball and lacrosse. This systematic review provides a summary of the ankle injury epidemiology in sports. 1. Introduction People from all around the world are participating in sports nowadays for personal interest, relaxation, health and fitness training. However, sports is one of the major causes of injuries which is comparable to traffic accidents, home and leisure accidents, occupational injuries, and violence [1-4]. Sports injuries result in pain, loss of playing or working time, as well as medical expenditure. Severe injuries may result in bone fractures, functional instability, limited mobility, disability, permanent cease of sports participation, psychological problem, and perhaps death. For world-class and commercial sports teams, absence of key players due to unexpected injuries may result in defeats in major games and huge economic loss. Due to these undesired adverse effects, scientists and medical specialists are actively working on sports injury prevention [5-7]. The aim is to prevent sports injury and let people enjoy sports participation. The first procedure to tackle a problem is to identify the problem. In 1970, Roser and Clawson conducted an epidemiology study on football injuries in young athlete [8]. In 1971, MacIntosh conducted similar study on athletic injuries in University of Toronto [9]. In 1972 and 1973, Garrick conducted related studies in prevention of sports injuries [5] and prevention of ankle sprains [10]. To be more specific in identifying the problem, Garrick pioneered a series of ankle sprains epidemiology studies from 1977 [11]. Subsequent studies by Garrick investigated ankle injuries in different sport events including aerobic dance [12] , children and adolescent skiing [13] , women gymnastics [14] , ballet [15] , and in all sports [16]. From 1980 afterwards, numerous epidemiology studies were conducted on different sports, population, g...