Injuries occurring to the posterior cruciate ligament (PCL) of the knee often occur with associated damage to the structures of the posterolateral corner, specifically the popliteus tendon (POP) and the popliteofibular ligament (PFL). During PCL reconstruction, it is often necessary to concurrently repair damage to the POP or PFL, with the intent of reducing external rotation of the tibia. This biomechanical study compared the efficacy of POP and PFL reconstructions in reducing external rotation and also compared differences in graft tensioning protocols when reconstructing these structures. Using a fresh frozen human cadaveric knee, external rotation in response to an external tibial torque and PCL graft tension forces were measured during a full range of motion. Both POP and PFL reconstructions were performed on the knee and compared individually with respect to external rotation in the same knee with the POP and PFL sectioned. Additionally, both the POP and PFL were reconstructed using two protocols: tensioning at 30 degrees of flexion allowing the knee to rotate freely and tensioning at 30 degrees with the knee locked in neutral rotation. We found the following: First, the POP and PFL reconstructions each were found to reduce the external rotation of the knee when compared to the knee without these structures intact. Second, both POP and PFL reconstructions produced similar reductions in external rotation. Finally, the two different tensioning protocols led to no significant differences in tension forces experienced by the PCL, but tensioning the graft in locked neutral rotation led to a greater amount of external rotation over the full range of motion.