Lateral extraarticular reconstructions are used as iso lated procedures in knees with moderate rotatory insta bility and as “backups” in knees requiring primary repair or intraarticular reconstruction for major rotatory insta bility. We used an experimental knee testing system to analyze the immediate postoperative mechanical effect of an iliotibial band tenodesis on an intraarticular recon struction of the ACL in fresh cadaver knees using a composite graft consisting of a bone-patellar tendon- bone segment augmented with the Kennedy Ligament Augmentation Device (LAD, 3M Co., St. Paul, MN). The intraarticular graft was standardized by using a force- setting technique. Ligament and graft forces were measured using buckle transducers, and joint motion was measured using an instrumented spatial linkage as 90 N anteriorly directed tibial loads were applied to seven fresh knee specimens at 0°, 30°, 60°, and 90° of flexion. The following knee states were tested in each specimen: intact ACL, excised ACL, intraarticular reconstruction, intraarticular reconstruction with the tenodesis added, and tenodesis with the intraarticular reconstruction added. Adding the iliotibial band tenodesis to an existing standardized intraarticular reconstruction significantly decreased the force in the ACL composite graft by an average of 43%. When the standardized intraarticular reconstruction was added to an existing tenodesis, the graft forces were an average of 15% below the level of when the reconstruction was performed alone. The force in the tenodesis was significantly less than the composite graft force at extension; however, the differ ences between the tenodesis and total graft force were not significant from 30° to 90° of flexion. Load sharing appeared to occur between the tenodesis and intraar ticular graft. The tenodesis caused the tibia to be in an externally rotated configuration relative to normal, po tentially interfering with the “screw home mechanism.”.