Make sure that the hamstring is relaxed or it can produce a false test result. Holding the lower part of the athlete's thigh in one hand and the upper part of the athlete's calf in the other, slowly pull the tibia forward. Increased looseness in the knee joint is indicative of an ACL injury. Any looseness in the joint could indicate ACL injury. The foot of the injured side is lifted with the leg straight and the foot turned inward.
Pressure is applied to the outside of the knee while the knee joint is slowly bent.
An ACL injury is detected if the tibia moves out of joint at 30-40 degrees or if a clunk is felt. One should note that this test can be very painful for the athlete. The athlete also needs to limit physical activity. A non-athletic person can live with the injury using rehabilitation and bracing. When the ACL is injured the guide wire of the knee is gone, creating instability.