The breakage of component is rare in TKA and usually restricted to hinges and linked design. Occasionally fracture of metal tibial component has been noted, but fracture of the femoral component has been rarely reported and occurred to be a significaot problem in TKA. This study reports 2 cases of femoral component fracture using Whiteside Ortholoc total knee system and analyzes the cause of this phenomenon. One pahent, a 67 years old female who weighed 74kg, was performed 1ke left TKA using Whiteside Ortholoc g system with cement. The size of feraoral component was small plus, and small tibial component, 14mm tibial insert and 28mm pateBa were used, The medial site of femoeal component fractured at 38 months postoperatively. A second female patient, who weighed 68kg and was 64 years old at the time of surgery, had also the left TKA using a medium sized femoral component of Whiteside Ortholoc modular system with cement. The small-Ex large tibial component, 8rrun tibial insert were used, but did not replace the pateBa. Also at 37 mainths postaperatively the medial site of femoral compcnent fractured, Ail cases were revised with using a cemented P,F.C. Modular Total Knee System (Johnson k Johnson). All two cases were kactured at the junction between the posterior bevel md distal surface of the medial femoral condyle. The thickness and length of Whiteside Ortholoc femoral component are thinner and shorter at posterior bevel surface compared with other TKA systems. So it is encouraging that a minor design modification of Whiteside Ortholoe femoral component and also should be edueated for the prohibihon of excessive flexion of the knee joint after TKA.