A new fluoroarthroscopic technique for the installation of an allograft ligament to replace an anterior cruciate ligament (ACL) function is described. Failure of any device intended to function as an ACL, biologic or prosthetic, will occur if the principles of isometry and instant centers of motion in relation to sites of ligament origin and insertion are ignored. At least equal preoperative planning and precise measurements should be made regarding ACL reconstruction as is presently required for the total-kneereplacement technique. The former is certainly less forgiving than the latter.The cruciate ligament organ obeys the principles of a four-bar, chain-link system. Abnormal compression and distraction forces will occur at the articular surface of the knee if points of contact (between the femur and the tibia) are changed due to an abnormally reconstructed ACL.Human cadaver knee dissections were performed. ACLs were opaquely tagged and their radiologic shadows studied fluoroscopically. Instant centers of motion were tested to determine acceptable surgical sites of origin and insertion of the intended ACL allograft.The site of femoral attachment was found fluoroscopically to exist 3 mm anterior to the junction of the posterior femoral cortex and the intercondylar cortical seam. A new attachment device has been developed to allow attachments of the allograft to the femur without the need for a posterolateral incision.The success of the reconstruction is a function of graft physiology, correct interpretation of knee biomechanics, and ultimately a long-term followup. The study is therefore a preliminary report emphasizing principles and surgical detail.