Isolated and Combined Posterior Cruciate Ligament Injuries.

Posterior cruciate ligament (PCL) injuries represent 3% to 20% of all knee ligamentous injuries, but the diagnosis often is missed at initial evaluation. Diagnostic acumen is increased by knowledge of knee biomechanics and selective ligament-cutting studies. The examiner must differentiate the isolated PCL injury from combined ligamentous injury to determine appropriate treatment. Isolated acute PCL tears with less than 10 mm of posterior laxity at 90 degrees of flexion should be treated with an aggressive rehabilitative program. This amount of laxity is found in the majority of isolated acute PCL tears. Isolated acute PCL tears with more than 10 to 15 mm of posterior laxity and PCL tears with combined ligamentous injuries should be reconstructed. Large PCL bony avulsions should be fixed internally. Small PCL bony avulsions with more than 10 mm of posterior laxity should be reconstructed. Chronic PCL injuries initially should be treated with an aggressive rehabilitation program. If such a program is not successful in a patient with more than 10 to 15 mm of posterior laxity and no significant radiographic evidence of degenerative changes, the PCL should be reconstructed.