Effect of torso position on arthrometric assessment of anterior knee laxity

The purpose of the study was to examine the effect of changes in torso position on arthrometric assessment of knee laxity. Anterior tibial translation (ATT) of 12 control and 12 ACL deficient subjects was assessed using a Dynamic Cruciate Tester during five maximal isometric knee extensions and five passive tests (240 N load) on the right and left knee in each of three torso positions: vertical, reclined, and supine. Electromyographic activity of rectus femoris, vastus lateralis, biceps femoris, and semimembranosus were sampled during arthrometric assessment. Results indicated there was no significant difference in mean ATT as a function of torso position. However, subjects demonstrated significantly greater hamstring activity when seated vertically compared to reclined or supine and significantly greater hamstring activity when reclined compared to supine.