The purpose of this paper is to evaluate the effectiveness of non-operative treatment of the isolated medial collateral ligament injuries of the knee using limited motion brace. Between Sep. 1987 and Oct. 1990, 21 isolated injuries of medial collateral ligament of the knee were treated by limited motion brace according to the treatment protocol of four basic phases. All of 12 patients of Grade II injuries were excellent in final assessment. All but one of 9 patients of Grade III injuries were excellent, and the one was good in final assessment. The key to suecess in this program was to rule out the injuries of anterior cruciate ligament by careful physical examination, K-T 1,000 knee arthrometer, and arthroscopy.