Objective evaluation of anterior knee laxity; comparison of the KT-1000 and GNRB® arthrometers

Accurate measurement of laxity after anterior cruciate ligament (ACL) rupture is usually performed with the KT-1000 arthrometer, and reproducibility and reliability are discussed. A new arthrometer, the GNRB(A (R)), has been recently developed in an attempt to improve intra- and inter-examiner reproducibility. The aim of this diagnostic study was to evaluate the intra- and inter-examiner reproducibility of the GNRB(A (R)) and the KT-1000. Three protocols were designed to evaluate and compare the two arthrometers. Fifteen physiotherapists conducted tests on 15 subjects with healthy knees. The intra- and inter-reproducibility of the two tests were compared by analysis of variance and the F-test. Measure reproducibility was significantly worst with the KT-1000 than with the GNRB(A (R)) (machine effect, P < 0.001) regardless of operator experience. There was no significant difference between experienced and inexperienced examiners with the GNRB(A (R)) (no 'examiners effect'). Regardless of the machine, there was a 'side effect' with healthy knees. This clinical study demonstrates the superior intra- and inter-examiner reproducibility of the GNRB(A (R)) over the KT-1000. There appears to be some technological advantages to using the GNRB(A (R)) including pressure control of the patella, accuracy of the displacement transducer, control of the load on the calf, and control of hamstring activity. Diagnostic study, Level I.