This paper describes a surgical navigation system for anterior cruciate ligament (ACL) reconstruction using an autostereoscopic image overlay technique. We superimpose a real three-dimensional (3-D) image onto the patient for image-guided therapy. The images are created by employing an animated visualization of integral videography (IV). IV records and reproduces 3-D images using a micro convex lens array and flat display; it can display geometrically accurate 3-D autostereoscopic images and reproduce motion parallax without the need for any special viewing or tracking devices. The use of semi-transparent display devices makes it appear that the 3-D image is inside the patient's body, which enables viewing the structure of ACL and detecting the position of femur, tibia and surgical tools. This is the first report of applying an autostereoscopic display with an image overlay system in ACL reconstruction surgery. Experiments demonstrated that the patient-image registration method and the fast IV rendering technique produce an average registration accuracy of 1.16 mm and frame rate of IV image display about 3 frames and 11 frames per second for organ and surgical tools respectively.