A process that utilizes a tendon threader for positioning and endosteally mounting a tendon within the endosteum of a closed tunnel end of a straight ligament tunnel that has been formed in a patient's knee in an arthroscopic surgical procedure for replacement of a cruciate ligament. The preferred tendon threader for use in a practice of the process includes a straight tubular body, with a handle arranged on one end, and the other tube end includes a pair of aligned wide longitudinal slots formed, with tube end remainder portions adjacent to which wide longitudinal slots each having a small longitudinal slot formed therein, the small slots for receiving a tendon, or a suture sewn onto the end of a tendon, fitted therein, forming a loop across the tube end. In a practice of the process the tendon threader is inserted into the straight ligament tunnel to where the tendon or suture loop is proximate to a ligament tunnel section end. Which procedure may be observed on a fluoroscopic monitor or utilizing an arthroscope fitted in the tendon threader tubular body. Whereat, a surgeon turns a pin into the side of the patient's knee, that travels through the ligament tunnel section and through the tendon or suture loop. The tendon threader is then removed leaving the tendon or suture folded over the pin, which tendon or suture end is then pulled over the pin to where the tendon ends are positioned over one another for mounting, under tension, as by stapling, onto the bone cortex surface adjacent to the straight ligament open tunnel end, completing the ligament mounting.