Posterior dislocation of the sternoclavicular joint is uncommon, accounting for less than 0.1% of all dislocations. Since 1824 a little more than 100 cases have been reported, and the majority in the past 20 years. A review of published reports suggests that this injury is seen particularly in connection with American football. A typical case is described. The importance of this injury is that there is often a delay in diagnosis with potentially serious complications.