ACL Anatomy

This section describes the ACL anatomy, including the bundles represented in the model and the femoral and tibial insertion sites.

General Description

  • Femoral insertion: posterior part of the inner surface of the lateral femoral condyle [DBA+06]
    • Size can vary from 11 to 44 mm across (‘across’ not defined) [DBA+06]
  • Tibial insertion: a fossa located anterior and lateral to the medial tibial spine. Fibers ‘fan out’ as they approach the tibial insertion. [DBA+06]
    • The fosa is approximately 11 mm wide (range of 8 to 12 mm), and the anterior-posterior length is 17 mm (range, 14–21 mm) [DBA+06]
  • Length: 22 to 41 mm (mean 32 mm) [DBA+06]

This lab models the ACL as two distinct bundles, the anteromedial (amACL) and the posterolateral (plACL) bundles. These names are derived from their insertion on the tibial plateau.

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Fig. 3 The amACL (labeled AMB) and plACL (labeled PLB) bundles [DBA+06].

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Fig. 4 The amACL and plACL femoral insertions [PZ07].

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Fig. 5 General tibial insertions of the amACL and plACL bundles [TLG+18].

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Fig. 6 Segmentation of the amACL and plACL bundles [TLG+18]. This shows one way to differentiate between the AM and PL bundles in the MR images.

amACL

  • Femoral insertion: The most superior and anterior part of the insertion
  • Tibial insertion: The most anteromedial aspect of the tibial insertion
  • Length: 34 mm in extension (like most MR images used in the lab) [DBA+06].

Note

When modeling the ligament as a bundle of nonlinear springs that are linearly mapped across the insertion site:
  • The femur’s proximal point corresponds with the tibia’s more anteromedial point
  • The femur’s distal point corresponds with the tibia’s more posterolateral point

plACL

  • Femoral insertion: The most distal and posterior part of the insertion
  • Tibial insertion: The most posterolateral aspect of the tibial insertion
  • Length: 22.5 mm in extension (like most MR images used in the lab) [DBA+06].

Note

When modeling the ligament as a bundle of nonlinear springs that are linearly mapped across the insertion site:
  • The femur’s proximal point corresponds with the tibia’s more anterior point
  • The femur’s distal point corresponds with the tibia’s more posterior point

[DBA+06](1, 2, 3, 4, 5, 6, 7, 8) V. B. Duthon, C. Barea, S. Abrassart, J. H. Fasel, D. Fritschy, and J. Ménétrey. Anatomy of the anterior cruciate ligament. Knee Surgery, Sports Traumatology, Arthroscopy, 14(3):204–213, March 2006. URL: http://link.springer.com/article/10.1007/s00167-005-0679-9, doi:10.1007/s00167-005-0679-9.
[PZ07]Wolf Petersen and Thore Zantop. Anatomy of the Anterior Cruciate Ligament with Regard to Its Two Bundles. Clinical Orthopaedics and Related Research®, 454:35, January 2007. URL: https://journals.lww.com/clinorthop/Fulltext/2007/01000/Anatomy_of_the_Anterior_Cruciate_Ligament_with.9.aspx, doi:10.1097/BLO.0b013e31802b4a59.
[TLG+18](1, 2) Yasutaka Tashiro, Gian Andrea Lucidi, Tom Gale, Kanto Nagai, Elmar Herbst, James J. Irrgang, Yasuharu Nakashima, William Anderst, and Freddie H. Fu. Anterior cruciate ligament tibial insertion site is elliptical or triangular shaped in healthy young adults: high-resolution 3-T MRI analysis. Knee Surgery, Sports Traumatology, Arthroscopy, 26(2):485–490, February 2018. URL: https://link.springer.com/article/10.1007/s00167-017-4607-6, doi:10.1007/s00167-017-4607-6.