Clinical tests versus KT-1000 instrumented laxity test in acute anterior cruciate ligament tears.

Forty-two patients referred to the outpatient clinic of Hagavik Orthopaedic Hospital within 3 weeks after an acute knee injury was found by arthroscopy to have a partial or total tear of the anterior cruciate ligament (ACL). In these patients, the results of clinical tests and instrumented laxity tests without anesthesia prior to the arthroscopy were analyzed. The Lachman test and the maximum anterior pull (150-200 N) KT-1000 instrumented test revealed abnormal laxity in 33 and 37 of 42 cases, respectively. Both tests revealed abnormal laxity more often than the KT-1000 test using 67 N (10/42) and the maximum anterior pull KT-1000 instrumented test also revealed abnormal laxity more often than the KT-1000 test using 89 N (25/42). By logistic regression analysis, the maximum anterior pull KT-1000 instrumented test was associated with rupture of the ACL (partial or total rupture). The results show that adequate anterior pull has to be used to overcome muscle tension to reveal abnormal laxity in acute ACL tears using the KT-1000 arthrometer.