Calcification most frequently occurs in the rotator cuff insertion of the shoulder. However, calcification is known to develop in any joint, including the hip, knee, wrist and elbow. Around the knee joint, it usually occurs in the areas such as the quadriceps femoris muscle, the popliteus muscle and the medial collateral ligament with a history of trauma. But the occurrence of calcification in the lateral collateral ligament is very rare. We herein report on one case of the calcification that developed in the lateral collateral ligament, and this was treated by excision of the calcified materials and repair of the ligament. We also present the magnetic resonance imaging findings of this case.