been shown to be lower when using autograft as compared to allograft. Hamstring tendon Hamstring autografts are made with the semitendinosus tendon, either alone or accompanied by the gracilis tendon for a stronger graft. The semitendinosus is an accessory hamstring (the primary hamstrings are left intact), and the gracilis is not a hamstring, but an accessory adductor (the primary adductors are left intact as well). The two tendons are commonly combined and referred to as a four-strand hamstring graft, made by a long piece (about 25 cm) removed from each tendon. The tendon segments are folded and braided together to form a tendon of quadruple thickness for the graft. The braided segment is threaded through the heads of the tibia and femur, and its ends are fixed with screws on the opposite sides of the two bones. Unlike the patellar ligament, the hamstring tendon's fixation to the bone can be affected by motion after surgery. Therefore, a brace is often used to immobilize the knee for one to two weeks. Evidence suggests that the hamstring tendon graft does as well, or nearly as well, as the patellar ligament graft in the long term. Common problems during recovery include strengthening of the quadriceps, IT-band, and calf muscles. The main surgical wound is over the upper proximal tibia, which prevents the typical pain experienced when kneeling after surgery. The wound is typically smaller than that of a patellar ligament graft, and so causes less post-operative pain. Another option first described in 2004, a minimally invasive technique for harvesting from the back of the knee, is faster, produces a significantly smaller wound, avoids the complications of graft harvesting from the anterior incision, and decreases the risk of nerve injury. There is some controversy as to how well a hamstring tendon regenerates after the harvesting. Most studies suggest that the tendon can be regenerated at least partially, though it will still be weaker than the original tendon. Advantages of hamstring grafts include their high "load to failure" strength, the stiffness of the graft, and the low postoperative morbidity. The natural ACL can withstand a load of up to 2,160 newtons. With a hamstring graft, this number doubles, decreasing the risk of re-injury. The stiffness of a hamstring graft—quadruple that of the natural ACL (Bartlett, Clatworthy and Ngugen, 2001)—also reduces the risk of re-injury. Patellar tendon The patellar tendon connects the patella (kneecap) to the