RESUMO
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 degrees , 45 degrees , and 60 degrees with the knee at 30 degrees of flexion. Anterior-posterior, valgus-varus, and rotational knee laxity were quantified. After sequential rotational torque to 60 degrees , the specimens were dissected to identify injured structures. RESULTS: External rotational torque of 45 degrees and 60 degrees 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 degrees 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.
