We performed instrumented measurement of anterior-posterior laxity of the knee in 33 cadaver specimens, 338 normal subjects, and 89 patients with unilateral disruption of the anterior cruciate ligament. The test instrument was the Medmetric knee arthrometer, model KT-2000. We measured total anterior-posterior laxity, produced by anterior and posterior loads of 89 newtons (20 pounds), and the anterior compliance index. The total anterior-posterior laxity is composed of an anterior displacement and a posterior displacement; these are measured from a testing reference position, defined as the resting position of the knee after applying and then releasing a posterior load of 89 newtons. The anterior compliance index is defined as the anterior displacement between an anterior load of 67 newtons and one of 89 newtons. All tests were performed with the knee held on a thigh support that placed the knee in 20 +/- 5 degrees of flexion. The mean anterior displacement at 89 newtons was 5.7 millimeters in a group of normal subjects and 13.0 millimeters in a group of patients with a disrupted anterior cruciate ligament. 92 per cent of the normal subjects had a left knee-right knee difference in anterior displacement of no more than 2 millimeters, while 96 per cent of the patients with a unilateral disruption of the anterior cruciate ligament had an injured knee-normal knee difference in anterior displacement of more than 2 millimeters. 93 per cent of the normal subjects had a difference in the left-right compliance index of no more than 0.5 millimeter, and 85 per cent of the patients with unilateral disruption of the anterior cruciate ligament had a difference in the compliance index of the injured and normal sides of more than 0.5 millimeter.
Copyright remains with the authors and publisher.
We performed instrumented measurement of anterior-posterior laxity of the knee in 33 cadaver specimens, 338 normal subjects, and 89 patients with unilateral disruption of the anterior cruciate ligament. The test instrument was the Medmetric knee arthrometer, model KT-2000. We measured total anterior-posterior laxity, produced by anterior and posterior loads of 89 newtons (20 pounds), and the anterior compliance index. The total anterior-posterior laxity is composed of an anterior displacement and a posterior displacement; these are measured from a testing reference position, defined as the resting position of the knee after applying and then releasing a posterior load of 89 newtons. The anterior compliance index is defined as the anterior displacement between an anterior load of 67 newtons and one of 89 newtons. All tests were performed with the knee held on a thigh support that placed the knee in 20 +/- 5 degrees of flexion. The mean anterior displacement at 89 newtons was 5.7 millimeters in a group of normal subjects and 13.0 millimeters in a group of patients with a disrupted anterior cruciate ligament. 92 per cent of the normal subjects had a left knee-right knee difference in anterior displacement of no more than 2 millimeters, while 96 per cent of the patients with a unilateral disruption of the anterior cruciate ligament had an injured knee-normal knee difference in anterior displacement of more than 2 millimeters. 93 per cent of the normal subjects had a difference in the left-right compliance index of no more than 0.5 millimeter, and 85 per cent of the patients with unilateral disruption of the anterior cruciate ligament had a difference in the compliance index of the injured and normal sides of more than 0.5 millimeter.
Copyright remains with the authors and publisher.