Knee dislocations are relatively uncommon but potentially catastrophic injuries. In athletes, these injuries generally result from high-energy traumatic mechanisms such as collisions in football and rugby, high-velocity falls in skiing, and falls from heights in gymnastics and extreme sports. Knee dislocations are frequently associated with coincident neurological or vascular injuries. Recognition of vascular injury is particularly challenging because vascular compromise may not be immediately associated with clinical signs of ischemia and may result from injuries without complete or evident dislocation. This article reviews the rationale behind selective angiography, adjunctive vascular testing, and the need for observation after multiligament knee trauma. An algorithm for the diagnosis of vascular injuries is presented.