What portion of the anterior cruciate ligament is most often injured when the knee is in extension?

• A. Anterior bundle
• B. Posterior bundle
• C. Medial bundle
• D. Laterl bundle

Answer: (B)

The posterior bundle of the anterior cruciate ligament (ACL) is the portion most often injured when the knee is in extension. When the knee is in an extended position, the ACL is at its most taut state, particularly the posterior bundle. This area is more prone to stress during activities that involve sudden changes in direction, jumping, or landing, which can lead to a higher risk of injury.

In addition to the posterior bundle being under significant tensile stress, the extension position places the knee in a biomechanically vulnerable position, which can lead to additional strain on the ACL if other forces (such as external rotation or varus/valgus stress) are applied. This highlights the anatomical and functional considerations of the ACL, emphasizing how its different bundles respond under varying mechanical stresses.

The anterior bundle, medial bundle, and lateral bundle do not primarily focus on the extension of the knee and are not the portions typically associated with injury in that position. Understanding the specific dynamics of the ACL's anatomy is crucial for identifying injury mechanisms and improving prevention strategies in sports and rehabilitation.