Alternatively, surgeons can balance the extension gap before the flexion gap. Using this technique, the distal femur is resected using an intramedullary guide followed by proximal tibial resection perpendicular to the longitudinal tibial axis. All osteophytes, including those on the femoral and tibial sides, are removed at this point, before any soft tissue release is performed because of their tensioning effect on adjacent ligamentous structures [21].

After the extension gap resection and osteophyte removal, gap symmetry, soft tissue balance, and lower extremity alignment are assessed. This assessment is achieved by placing a spacer block or tensioner into the extension gap (Fig. 6.4). Once ligament imbalance is checked, tight ligamentous structures are released until the extension gap is symmetric.

Once the knee is balanced symmetrically in extension, the goal is to balance the flexion gap and the extension gap. Spacer blocks can be used to apply equal tension to the collateral ligaments with the knee at 90 degrees of flexion. The transepicondylar and AP axis are constructed and used as a secondary indicator of femoral component rotation. When the knee is well balanced in extension and the tibial resection is precise, the resected proximal tibia should be parallel to the TEA and perpendicular to the AP axis (Fig. 6.5).

The appropriately sized AP femoral cutting block is then applied and inserted until it is parallel with the resected proximal tibia (Fig. 6.6). By adjusting the AP cutting block anteriorly or posteriorly, a flexion gap width is created as to be the same as the extension gap. In order to confirm the flexion-extension gap symmetry, the same spacer block used to check the extension gap is placed under the AP cutting block and above the resected proximal tibia, and flexion gap tension is again assessed before resection of the posterior femoral condyles.