A knee injury should be diagnosed and treated quickly (in order to reduce the time of disability and the emergence of late complications). Dislocation of the knee joint (possible vascular damage; does not apply to the dislocation of the patella) and all open injuries warrant immediate referral. If several ligaments are involved and valgus or varus deformity can be produced with the knee extended, the patient needs to be referred quickly, perhaps on the following day.