This patient has two problems: 1) loose in flexion (flexion laxity); 2) tight in extension (flexion contracture). Both of these should be addressed in surgery. In order to address the flexion instability, the surgeon can either upsize the femoral component or posteriorly translate the femoral component. Increasing the poly thickness will help the flexion instability, but worsen the tightness in extension. In order to address the extension tightness, the surgeon can downsize the poly insert, resect additional tibia, or resect additional distal femur. Downsizing the poly and resecting additional tibia, however, will both result in increased flexion instability. Resecting additional distal femur only affects the extension gap. Thus, the correct answer is upsizing the femoral component and resecting additional femur.
Vail TP, Lang JE: Surgical techniques and instrumentation in total knee arthroplasty, in Scott WN (ed): Surgery of the Knee, ed 4. Philadelphia, PA, Churchill Livingstone, 2006, pp 1553-1621
Callaghan JJ, Rosenberg AG, Rubash HE, et al: The Adult Knee. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 1217-1223