Thirteen subjects who had normal knees and fifteen patients who had a
chronic rupture of the anterior cruciate ligament were tested in order to
compare the measurements of tibiofemoral displacement as recorded by four
commercial devices: the Acufex knee-signature system, the Genucom
knee-analysis system, the Medmetric KT-1000 arthrometer, and the Stryker
knee-laxity tester. Anterior and posterior displacement were measured at
forces of eighty-nine newtons (twenty pounds) and 133 newtons (thirty
pounds). We found significant differences in reproducibility of measurement
among the devices. The Acufex, Medmetric, and Stryker devices had more
reproducible measurements, and they could be used to identify 80 to 90 per
cent of the normal subjects and anterior cruciate-deficient patients. The
Genucom device had poorer reproducibility of measurement, and it tended to
register greater differences in displacement between the right and left
knees of normal subjects.