Reliability of KT1000 Knee Arthrometer Measures Obtained at Three Knee Joint Positions

Abstract: The reliability of KT1000 knee arthrometer measurements has been established at a flexion angle of 20° to 30°. However, no studies have assessed its reliability at multiple joint positions. This study was conducted in order to compare the displacement at three positions (20°, 45°, and 90°) and to determine the test-retest reliability at each position. Twenty subjects having no history of knee pathology participated in the study. A KT1000 knee arthrometer (MEDmetric Corporation, San Diego, CA) was positioned on the leg to measure anterior displacement of the proximal tibia at the three knee joint positions in random order. Post-hoc analysis indicated greater displacement at the 20° and 45° positions than at the 90° position. Intraclass correlation coefficients for the test-retest sessions were R=.92, .84 , and .90 for the 20°, 45°, and 90° positions, respectively. These findings suggest that the KT1000 is a reliable instrument for measurement of passive anterior displacement throughout the knee joint's range of motion. Injury to the anterior cruciate ligament may involve rupture of the entire ligament, or may be isolated to a particular portion of the ligament. As such, assessment of anterior displacement at multiple joint angles is recommended to most accurately evaluate the integrity of the anterior cruciate ligament. Article: The recent development of knee arthrometers has enabled objective measurement of knee joint displacement. The KT1000 arthrometer (MEDmetric Corporation, San Diego, CA), the Stryker knee laxity tester (Stryker, Kalamazoo, MI), and the Genucom knee analyzer (FARO Medical Tech. Inc., Montreal, Canada) are examples of instruments that have been designed to objectively measure laxity of the knee joint. These instruments appear to be correct 70 to 75% of the time in determining cruciate ligament integrity (1). The results of arthrometer measurements help to increase confidence in clinical diagnosis. Several investigators have examined the reliability of these instruments with the knee in a flexion angle of 20° to 30°. Highenboten et al. (8) found that the three previously-mentioned knee laxity testing devices provided reproducible quantitative measurements of knee laxity. Others have reported high correlation coefficients for the KT1000 with the knee in the standard 20° to 30° flexion angle (2,6). However, the reliability of measurement with this instrument at multiple joint positions has not been established