ACL Surgery Graft Options

ACL reconstruction is a surgical procedure to replace the torn ligament for someone who has sustained an ACL tear. Once an individual has decided to have surgery, they will have to make several decisions about their surgery with their doctor. The most common question patients face is: which type of ACL graft should they choose?

The ACL graft is the type of tissue used to create the new ACL ligament. ACL reconstruction can be done with several different graft choices. The most common options include patellar tendon, hamstring tendon, and donor tissue (allograft). Each of these choices has advantages and disadvantages.

Athletic invasive knee surgery, repairing ligaments
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Repair vs. Reconstruction

ACL surgery is commonly, but not correctly, referred to as an ACL repair. A repair implies that you can fix something that is torn or broken. If an ACL is completely torn, the ends of the torn ligament will not heal back together, even if the torn ends were sewn together.

What has been shown to be successful: removing the torn ends of the ACL and replacing the ligament with a different structure—a procedure called an ACL reconstruction. A graft is tissue that is moved from one location to another. When the source of the graft is from the individual having surgery, it is called an autograft. When the source is from a donor (cadaver), it is called an allograft.

To secure the grafted ligament into the position of the normal ACL, tunnels are made in the shin bone (tibia) and thigh bone (femur), and the graft is passed through these tunnels to reconstruct the ligament.

Patellar Tendon Autograft

The patellar tendon is the structure on the front of your knee that connects the kneecap (patella) to the shin bone (tibia). The patellar tendon averages between 25 to 30 mm in width. When a patellar tendon graft is selected, the central one-third of the patellar tendon is removed (about 9 or 10 mm) along with a block of bone at the sites of attachment on the kneecap and tibia.

  • Advantages: Many surgeons prefer the patellar tendon graft because it closely resembles the torn ACL. The length of the patellar tendon is about the same as the ACL, and the bone ends of the graft can be placed into the bone where the ACL attaches. This allows for "bone to bone" healing, something many surgeons consider to be stronger than any other healing method.
  • Disadvantages: When the patellar tendon graft is taken, a segment of bone is removed from the kneecap, and about a third of the tendon is removed. There is a risk of patellar fracture or patellar tendon tear following this surgery. In addition, the most common problem following this surgery is a pain on the front of the knee (anterior knee pain). In fact, patients sometimes say they have pain when kneeling, even years after the surgery.

Hamstring Tendon Autograft

The hamstring muscles are the group of muscles on the back of your thigh. When the hamstring tendons are used in ACL surgery, one or two of the tendons of these muscles are removed and "bundled" together to create a new ACL. Over the years, methods of fixing these grafts into place have improved.

  • Advantages: The most common problem following ACL surgery using the patellar tendon is pain over the front of the knee. Some of this pain is known to be due to the graft and bone that is removed. This is not a problem when using the hamstring tendon. The incision to obtain the graft is smaller, and the pain both in the immediate postoperative period and down the road is thought to be less.
  • Disadvantages: The primary problem with these grafts is the fixation of the graft in the bone tunnels. When the patellar tendon is used, the bone ends heal to the bone tunnels ("bone-to-bone" healing). With the hamstring grafts, a longer period of time may be necessary for the graft to become rigid.

Allograft (Donor Tissue)

Studies have suggested that allograft (donor tissue from a cadaver) has higher failure rates in patients under the age of 25. For many recreational athletes, the strength of the reconstructed ACL using an allograft is sufficient for their demands, and allografts appear to provide equal stability to autografts. Therefore, this may be an excellent option for older patients or for patients who do not want to have a tendon taken from another part of their knee.

  • Advantages: Performing ACL surgery using an allograft allows for decreased operative time, no need to remove other tissue to use for the graft, smaller incisions, and less post-operative pain. Furthermore, if the graft were to fail, revision surgery could be performed using either the patellar tendon or hamstring grafts.
  • Disadvantages: Historically, these grafts were of poor quality and carried a significant risk of disease transmission. More recently, techniques of allograft preparation have improved dramatically, and these concerns are less of an issue. However, the process of graft preparation (freeze-drying) kills the living cells and decreases the strength of the tissue. The risk of disease transmission also still remains. While sterilization and graft preparation minimizes this risk, it does not eliminate it entirely.

How to Choose an ACL Graft

Many surgeons have a preferred type of graft for different reasons. The strength of patellar tendon and hamstring grafts is essentially equal. There is no right answer regarding which is best, at least not one that has been proven in scientific studies.

The strength of allograft tissue is less than the other grafts, but the strength of both the patellar tendon and hamstring tendon grafts exceed the strength of a normal ACL. The bottom line is that 75% to 90% of all patients will have clinically stable knees following ACL reconstructive surgery.

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