This study aims to quantify the relationship between distal femoral bone resection and correction of fixed flexion in total knee arthroplasty (TKA). Two previous studies have reported conflicting results. Spacers attached to the trial femoral component simulated additional distal femoral resection and the degree of knee flexion was recorded using computer navigation. The 2-mm augment produced an average of 3.37° of flexion deformity, 4-mm augment 6.68°, and 6-mm augment 11.38°. The amount of pre-resection flexion contracture significantly impacted on the effect of each augment. From our results, an additional 3.55 mm of distal femoral bone resection is required to correct 10° fixed flexion and produced less correction of flexion deformity as traditionally believed in TKA.