The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee.The purpose of the ACL is to resist the motions of anterior tibial translation and internal tibial rotation; this is important to have rotational stability. This function prevents anterior tibial subluxation of the lateral and medial tibiofemoral joints. The ACL has mechanoreceptors that detect changes in direction of movement, position of the knee joint, and changes in acceleration, speed, and tension. A key factor in instability after ACL injuries is having altered neuromuscular function secondary to diminished somatosensory information. For athletes who participate in sports involving cutting, jumping, and rapid deceleration, the knee must be stable in terminal extension.The ACL can be injured or torn in a number of different ways. The most common mechanism is that of a sudden pivoting or cutting maneuver during sporting activity, which is commonly seen in football, basketball and soccer. The ligament can also tear due to work injuries or automobile accidents.At the time of the injury, a “pop” or “snap” can sometimes be felt or heard. The amount of pain experienced at the time of the injury is somewhat variable but can be quite severe. Typically, the person is unable to continue play or activity, and has the impression that a significant injury has occurred.

During ACL reconstruction surgery, a graft is used to replace the torn ACL. One option for the graft is to use the hamstring tendons, specifically the semitendinosus and gracilis tendons, which are located at the back of the thigh. These tendons are often selected due to their accessibility, strength, and potential for successful incorporation into the knee joint.The surgical procedure involves harvesting the hamstring tendons, usually through a small incision near the knee. The tendons are then prepared by removing any excess tissue and folded over to create a stronger graft. The graft is then inserted into the knee joint, passing through tunnels drilled in the tibia and femur, to mimic the function of the original ACL.

Graft strength is only one of the factors influencing anterior cruciate ligament (ACL) graft choice.However, it has a direct bearing on ultimate stability,which is the goal of ACL.Load to failure (LTF) is the parameter used to compare strenghth of graft.10-mm BPTB graft would be 110% as strong as the native ACL. A two-strand semitendinosus (ST) and two-strand gracilis (Gr) (2ST/2Gr)graft would be 238% as strong as the native ACL.A four-strand ST (4ST) would be 280% as strong as the ACL.Four-strand hamstring autografts are the strongest available grafts,followed by tibialis, QT, and BPTB grafts, with insufficient data to evaluate Tendo Achilles grafts. All have greater strength than the native ACL.Graft strength is only one of many factors contributing to knee stability after ACL reconstruction.grafts retain only about half their initial strength at long-term follow-up. Thus, grafts that are significantly stronger than the native ACL at time zero may indeed be necessary to produce ultimate strengths that are as strong as the ACL initially was.Allografts are increasing rapidly in populari