What is a hamstring autograft ACL reconstruction?
The anterior cruciate ligament (ACL) is one of the main ligaments inside the knee. It helps keep the shin bone (tibia) from sliding forwards and rotating under the thigh bone (femur), especially during pivoting and changing direction. A hamstring autograft ACL reconstruction replaces a torn ACL with a new ligament made from your own hamstring tendons ("autograft" means tissue taken from your own body). The tendons usually used are the semitendinosus and often the gracilis, which run along the inner side of the back of the thigh and attach to the upper shin. They are taken out through a small incision on the front and inner side of the upper shin and folded to make a thicker graft, commonly with four strands (PMID 32387652). Hamstring tendons are one of the two most commonly used grafts for ACL reconstruction, and in the Scandinavian knee ligament registries they were used in 84.1% of 45,998 primary reconstructions (PMID 25201444; PMID 28888527).
The operation is minimally invasive and is done with a knee arthroscopy (a camera inserted through small incisions). Tunnels are drilled in the thigh bone and the shin bone at the attachment points of the original ACL, and the graft is passed through them and fixed in place, so that it sits in the same position and orientation as the ligament it replaces. Over the following months, the graft heals into the bone tunnels. It is one of the graft options for ACL reconstruction, and in some knees it is combined with a lateral extra-articular tenodesis to add control of rotation.
A thorough clinical examination by a specialist and modern imaging helps confirm the diagnosis. Examination tests such as the Lachman test and the pivot shift test are accurate for detecting an ACL tear (PMID 26854045), and MRI shows the ligament and any injury to the meniscus and cartilage. Some meniscus tears are hard to see on MRI, so the arthroscopy at the start of the operation is also used to assess the joint and treat any other injuries found (PMID 31684739).
What are the benefits of a hamstring autograft ACL reconstruction?
A hamstring graft restores a stable knee with results similar to those of the other main graft, the patellar tendon. A Cochrane review of 19 randomised trials (1,597 patients) found no differences between the two grafts in knee function scores, hop testing, return to activity or rupture of the graft (PMID 21901700). Trials followed up for an average of about 15 years also showed no differences in knee looseness or clinical outcome scores (PMID 35721585).
The hamstring graft is kind to the front of the knee. Compared with a patellar tendon graft, it was associated with 69% lower odds of pain at the front of the knee or difficulty kneeling (PMID 37000243), and with less anterior knee pain at five years or more after surgery (PMID 32387652). In one long-term trial, osteoarthritis on X-ray was less common after a hamstring graft than after a patellar tendon graft (PMID 35721585).
Most people return to sport. Across 69 studies (7,556 people) after ACL reconstruction, 81% returned to some sport, and having a hamstring graft was associated with returning to competitive sport (PMID 25157180). The harvested hamstring tendons often grow back: signs of tendon regeneration were found in about 86% of patients in a review of 19 studies (PMID 25557918).
What are the risks of a hamstring autograft ACL reconstruction?
The new graft can fail or tear again. In the Scandinavian registries, hamstring grafts had a higher risk of revision surgery than patellar tendon grafts (the risk with patellar tendon grafts was about 37% lower) (PMID 25201444). A review of ACL registries found that younger age and the use of hamstring grafts were consistently linked with a higher risk of revision (PMID 32014408). A thinner graft is more likely to need revision, and the size of a person's tendons is difficult to predict before surgery (PMID 27002103).
Numbness of the skin is the most common problem related to taking the hamstring tendons. Injury to small skin branches of the saphenous nerve below the kneecap caused an area of reduced feeling in 39.7% to 88% of patients across studies (PMID 28888527). The direction of the incision may affect how often this happens (PMID 27338956).
Some loss of hamstring strength can remain. Compared with patellar tendon grafts, hamstring grafts led to a measurable loss of knee bending (flexion) strength and a trend towards some loss of knee bending, and the knee was slightly less tight on laxity testing, although the clinical importance of these differences is unclear (PMID 21901700). A weakness in deep knee bending is usually present after surgery, even when the tendons regrow (PMID 25557918).
Surgery does not guarantee a return to the previous level of sport. In the review of 7,556 people, 65% returned to their pre-injury level of sport and 55% to competitive sport (PMID 25157180). Other risks are those of knee surgery in general, such as infection, stiffness, blood clots, ongoing pain or swelling, and injury to the cartilage or meniscus in the future.
Summary
A hamstring autograft ACL reconstruction replaces a torn ACL with a graft made from your own hamstring tendons, placed through small tunnels in the thigh bone and shin bone, to restore stability to the knee. It is usually recommended when the expected benefits for you outweigh the risks. You should discuss your symptoms, your scans and your goals, including plans for sport and work, with your knee surgeon so that you can consider the graft options and the indications for surgery together.
General information only. The information on this page is general in nature and does not replace individual medical advice. All surgery carries risks, and results vary between patients. Please discuss your own circumstances with your treating practitioner.