Background: External rotational torque is one of the mechanisms that may occur during a pivoting or twisting injury to the knee.
Hypothesis: Simulated external rotational injury by applying external rotational torque will increase knee laxity and cause soft tissue damage to the knee.
Study Design: Controlled laboratory study.
Methods: Six cadaveric knees and a custom testing system were used to produce external rotational torque of 30°, 45°, and 60° with the knee at 30° of flexion. Anterior-posterior, valgus-varus, and rotational knee laxity were quantified. After sequential rotational torque to 60°, the specimens were dissected to identify injured structures.
Results: External rotational torque of 45° and 60° significantly increased knee joint laxity in all directions (P < .05). Dissection showed that all posterior cruciate ligaments were intact; all medial collateral and anterior cruciate ligaments revealed either partial or complete tears. The lateral collateral ligaments were torn in all specimens. The popliteus tendon was attenuated in 1 specimen and was completely torn in 1 specimen. The popliteofibular ligament was torn in 3 specimens.
Conclusion: External rotational torque to 60° increased knee laxity, and dissection revealed a consistent pattern of injury to the medial and lateral collateral and anterior cruciate ligaments and posterolateral corner.
Clinical Relevance: Because isolated ligament injuries are rare, recognizing these combined ligamentous injuries early is essential for repair in the acute stage.
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