What part of the ACL is tense in flexion?

The anteromedial bundle of the anterior cruciate ligament (ACL) is known to be tense when the knee is in a flexed position. This is primarily due to the anatomical alignment and functional role of the fibers in this bundle. During flexion, the anteromedial bundle becomes more taut, providing stability to the knee joint and preventing excessive movement that could lead to injury.

When the knee is bent, the tension in the anteromedial bundle plays a crucial role in resisting anterior translation of the tibia relative to the femur. This characteristic is essential for maintaining joint stability during activities that involve knee flexion, such as running, jumping, or changing directions.

The other bundles mentioned do not exhibit the same level of tension during knee flexion. For instance, the posterolateral bundle is typically more engaged in extension and does not contribute significantly to the tension in flexion. The intermediary and distal bundles are not well-recognized as distinct anatomical entities in the context of ACL function. Consequently, the focus on the anteromedial bundle's role in tension during flexion underscores its importance in stabilizing the knee in dynamic movements.