Figure 1. Lateral portal view of the two-bundle anatomy of the ACL of a left knee. The anteromedial (AM) and posterolateral (PL) bundle are indicated by the arrows.

Non-Anatomic ACL Reconstruction does not Promote Long-Term Knee Health
It has been shown that traditional non-anatomic single-bundle ACL reconstruction does not prevent the occurrence of early osteoarthritis2. This traditional ACL reconstruction technique places the ACL graft outside of the native insertion site3-4 and therefore fails to restore the normal knee kinematics5. It has been hypothesized that these abnormal knee kinematics contribute to the development of osteoarthritis after ACL reconstruction. Before we discuss whether to perform single- or double-bundle reconstruction, we first need to place the ACL in the anatomic position. Anatomic placement of the graft helps to restore normal knee anatomy and function and therefore helps to promote long-term knee health.

How Much of the ACL Do We Need to Restore?
The ACL comes in a variety of shapes and sizes (Figure 2). The native ACL insertion site size ranges from 12 mm to 22 mm4. A single tunnel of 10 mm diameter would cover 80-90% of the native ACL insertion site if the native ACL insertion site is only 12 mm. However, if the native ACL is 22 mm, a single tunnel of 10 mm diameter may only cover less than half of the native ACL insertion site. Double-bundle reconstruction would result in better coverage of the native insertion site in these cases. This illustrates that ACL reconstruction should be performed in an anatomic fashion; individualized to tailor the ACL to each patient's specific needs.


Figure 2. Lateral portal view of the tibial ACL insertion site. A. Tibial insertion site of 14 mm. B. Tibial insertion site of 22 mm. These examples show the large variation in ACL insertion site size.

The Two Bundles Work Together
The native ACL consists of two functional bundles that work synergistically. Together they provide stability, while allowing normal knee range of motion. Anatomic single-bundle ACL reconstruction restores the ACL as one bundle, while double-bundle ACL reconstruction restores the ACL as two bundles allowing each bundle to be tensioned separately to better replicate the native ACL tension pattern.

Outcome Evaluation
To determine if there is a difference in outcome between single- and double-bundle ACL reconstructions, we need high quality randomized clinical studies. However, we also need to focus on improving our outcome measures. Physical examination and patient reported outcome scores may not be enough to demonstrate the subtle, yet important differences between the techniques. More accurate, reliable and precise outcomes measures including biology, imaging and kinematic testing are needed.

The paradigm in ACL surgery is changing. New reconstruction techniques are being developed and there is a need to compare these various techniques. There is no definitive answer to whether single- or double-bundle reconstruction is better at this time. The best answer is that this probably depends on the patients' individual characteristics with regards to ACL size, activity level, co-morbidities and more. Regardless of the choice for single- or double-bundle, ACL reconstruction should be performed in an anatomic fashion. By restoring normal knee anatomy and kinematics, we can potentially eliminate risk factors and help to prevent the development of osteoarthritis. Osteoarthritis has a major impact on quality of life and its prevention is part of our vow to provide the best possible care for our patients.



  1. van Eck C.F., Lesniak B.P., Schreiber V.M., Fu F.H. Anatomic Single- and Double-Bundle Anterior Cruciate Ligament Reconstruction Flowchart. Arthroscopy 2010;26-2:258-68.
  2. Lohmander L.S., Ostenberg A., Englund M., Roos H. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum 2004;50-10:3145-52.
  3. Forsythe B., Kopf S., Wong A.K., Martins C.A., Anderst W., Tashman S., Fu F.H. The location of femoral and tibial tunnels in anatomic double-bundle anterior cruciate ligament reconstruction analyzed by three-dimensional computed tomography models. J Bone Joint Surg Am 2010;92-6:1418-26.
  4. Kopf S., Pombo M.W., Szczodry M., Irrgang J., Fu F.H. Size Variability of the Human Anterior Cruciate Ligament Insertion Sites. American Journal of Sports Medicine;In press.
  5. Tashman S., Collon D., Anderson K., Kolowich P., Anderst W. Abnormal rotational knee motion during running after anterior cruciate ligament reconstruction. Am J Sports Med 2004;32-4:975-83.