Eighty-three total knee arthroplasties done at a single university hospital were reviewed specifically to examine the presence of lysis. Components that were radiographically loose were excluded. The incidence of lysis varied significantly with the method of component fixation. The highest incidence of lysis (30%) was seen when the tibial component was fixed with cement and screws and the femoral component was implanted without cement. When the tibial component was fixed with cement and screws and the femoral component was cemented, the incidence of lysis was 13% (2 of 13). When the femoral component was press fit and the tibia was cemented without screws, the incidence of lysis was 10% (1 of 10). When the femoral and tibial components were cemented and no screws were used, the incidence of lysis was 0 (0 of 12). Using screws with cement to fix the tibial component was associated with a high incidence of lysis and cannot be recommended. A press fit femoral component also may contribute to the incidence of lysis.