The purpose of this study was to assess the risk of knee injuries among vulnerable road users, such as pedestrians, bicyclists and motorcyclists.Two different periods (years 1985-1993 and 1995-2003) were compared. Inclusion criteria were furthermore Abbreviated Injury Scale knee 2-3 (AIS(knee)). Technical analysis assessed the type of collision, direction and speed as well as the injury pattern, and different injury scores (AIS, ISS) were examined documented by the accident research unit, which analyses technical and medical data collected shortly after the accident at the scene. This study included 2,580 pedestrians, 2,279 motorcyclists and 4,322 bicyclists from a total number of 22,794 victims in 17,382 accidents.Among vulnerable road users, 2% (196/9181 patients) had serious ligamentous or bony injuries of the knee. The risk of injury was higher for motorcyclists and bicyclists than for pedestrians. Knee injury severity was higher for pedestrians. Over the course of 18 years, the knee injury risk was significantly reduced in more recent times (35%>28%, p<0.0001). Improved aerodynamic design of car fronts reduced the risk for severe knee injuries significantly (p=0.0015).The highest risk for knee injuries among vulnerable road users is encountered by motorcyclists followed by bicyclists and pedestrians. Over time, the knee injury risk for pedestrians could be significantly reduced due to aerodynamic changes of current car fronts. Further modification of the exterior car design might decrease the risk for knee injuries among vulnerable road users.