Injuries to the lateral and medial collateral ligaments are common, but the MCL injuries occur more often than the LCL injuries. 25% of the patients in the United States with an acute knee injury in the emergency rooms, have a collateral ligament injury. Adults of 20-34 and 55-65 years old have the highest incidence. LCL (and MCL) injuries occur equally for men and women as for different races. These injuries are succesfully treated with conservative methods. Even when surgery is necessary, there is normally a good prognosis.