To examine risk factors for shoulder injuries with or without history of the injuries using the stratification analysis for collegiate rugby players. 71 elite rugby players from one university rugby club joined in the preseason medical screening related to their shoulder joints, including basic demographics, history of injuries, and physical findings at that time. Subsequently, the occurrence of shoulder injuries was recorded during four playing seasons. Analysis was stratified with or without history of the injuries; player without the past history of injury, 47 players; player with the past history of injury, 24 players. As a result of all players with the past history, 13 players sustained the shoulder injuries. Internal rotational range of motion [IR ROM] (OR, 1.5; 95%CI, 1.13-1.96; p=0.004), external rotational range of motion [ER ROM] (OR, 1.9; 95%CI, 1.21-2.87; p=0.005), horizontal flexion range of motion [HF ROM] (OR, 1.3; 95%CI, 1.03-1.64; p=0.025), IR muscle strength (OR, 0.4; 95%CI, p=0.001) and rugby experience (OR, 1.2; 95%CI, 1.02-1.46; p=0.032) were associated with the shoulder injuries. On the other hand, 10 players sustained injuries of the players without the past history of injury. IR muscle strength (OR, 0.3; 95%CI, p=0.008) and rugby experience (OR, 1.4; 95%CI, 1.11-1.66; p=0.003) were associated with the shoulder injuries. This study clearly showed that IR, ER, HF ROM, IR muscle strength and rugby experience were important initial risk factors for shoulder injuries. Moreover, IR muscle strength and rugby experience were important recurrence risk factors for shoulder injuries.
