The effect of knee flexion angle on knee stiffness values obtained using the Leicester arthrometer.

Knee stiffness was measured in 20 patients with a unilateral ACL-deficiency at 0 degree, 20 degrees and 65 degrees of knee flexion, respectively. The reduction in stiffness when the ACL deficient knee was compared with the normal contralateral knee was 46, 39 and 39%. The differences between these values were not statistically significant. The data raise the possibility that the angle at which instrumented measurement is made may not be critical provided the deficient knee is compared with the normal knee at the same angle.