Diagnosis of an ACL disruption with KT-1000 arthrometer measurements

The KT-1000 was used to measure anterior tibial displacement in three populations: normal subjects (n = 120), patients with unilateral acute anterior cruciate ligament (ACL) disruptions (n = 105), and patients with chronic unilateral ACL disruptions who were scheduled for ACL reconstructions (n = 159). All patients with ACL disruptions were measured with and without anesthesia. Tibial displacement under three loading conditions was measured: 89-N anterior displacement force, manual maximum displacement force, and quadriceps contraction to lift the leg. The measurements of the normal knee in the injured populations were not significantly different from those of the knees in the normal population on any test. The injured knee tested with and without anesthesia was significantly different from the normal knee on all tests. The right-left difference in the normal population as less than 3 mm in 98% of patients in the 89-N test, 97% in the manual maximum test, and 99% in the quadriceps active test. The largest amount of displacement and the greatest difference in displacement between the injured and the normal knee was produced by the manual maximum test. The manual maximum injured-minus-normal knee displacement was 3 mm or more in 99% of patients with chronic ACL disruptions and in 95% of patients with acute ACL disruptions.