Fracture of the metal base of tihial components of total knee arthroplasty has heen occasionally reportecl. The most common cause of the failure of the metal hase plate was known to be a fatigue fracture around the screw hole where the strength of the metal hase plate was the weakest. We experienced a case of the fracture of the metal hase plate secondary to the t'racture of the posteromedial corner of the metal tihial condyle which was weakened due to the shoil peg hole for the base plate of MG II implant. Since the proximal portion of the posterior tihial condyle was normally thin, cutting the hone for the base plate made it thinner and wcaker than normal. Therefore stress fracture of the bone occurred and the overlying metal plate was subsequently hroken. From this experience. we concluded that the posterior peg hole may cause unwanted failure of the posteromedial corner of the tibial base plate.