The ACL has two functional bundles — the anteromedial (AM) and posterolateral (PL). The AM bundle is the primary restraint to anterior translation in the flexed knee and the primary bundle reconstructed in single-bundle ACL surgery. Double-bundle ACL reconstruction specifically reconstructs both bundles to more closely reproduce the native ACL's rotational stability.
| Origin | Anteromedial portion of the ACL femoral footprint on the medial wall of the lateral femoral condyle |
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| Insertion | Anteromedial portion of the ACL tibial footprint |
| Actions | Tight in knee flexion; primary restraint against anterior tibial translation in the flexed knee; key ACL bundle for single-bundle reconstruction |
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The AM bundle is the bundle tensioned by the Lachman test (anterior translation at 30 degrees of flexion). Single-bundle ACL reconstruction using the hamstring or bone-patellar tendon-bone graft primarily replicates the AM bundle. Double-bundle reconstruction adds a PL graft through a separate tibial and femoral tunnel, improving rotational stability in biomechanical studies.
Primary ACL bundle disruption producing anterior translation on Lachman test managed with single or double-bundle reconstruction.
