Common mechanisms of injury for knee ligaments

Anterior cruciate ligament (ACL)

May be injured through a noncontact twisting injury associated with hyperextension and varus or valgus stress to the knee. Other mechanisms of injury include the tibia being driven anteriorly on the femur, the femur being driven posteriorly on the tibia or severe knee hyperextension. Special tests: anterior drawer test, Lachman test, lateral pivot shift test, Slocum test.

Posterior cruciate ligament (PCL)

May be injured when the superior portion of the tibia is struck while the knee is flexed. Ex: a motor vehicle accident when a passenger's leg collides against the dashboard. Other mechanisms of in injusry include the tibia being driven posteriorly on the femur, the femur being driven anteriorly on the tibia or severe nee hyperflexion. Special tests: posterior drawer test and posterior sag sign.

Medial collateral ligament (MCL)

May be injusred with a pure valgus load at the knee without rotation. This type of injury is often sustained with contact activities such as a alteral blow to the knee during a football game. Often involves other knee structures such as the ACL or medial meniscus. Special tets: valgus stress test

Lateral collateral ligament (LCL)

May be injusred with pure varus load at the knee without rotation. Often sustained with contact activities such as a medial blow to the knee. LCL is rarely completely torn without a concurrent injury to the ACL and PCL. Special test: varus stress test