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 t ranslation (ATT) of 12 control and 12 ACL deficient subjects was asses sed 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, bicep s femoris, and semimembranosus were sampled during arthrometric assess ment. Results indicated there was no significant difference in mean AT T as a function of torso position. However, subjects demonstrated sign ificantly greater hamstring activity when seated vertically compared t o reclined or supine and significantly greater hamstring activity when reclined compared to supine. Relevance--The findings of this study ha ve provided a rationale for patient positioning during arthrometric as sessment of knee laxity. That is, to minimize potential for hamstring guarding which may compromise knee laxity results in the clinical sett ing, arthrometric assessment of knee laxity in the sagittal plane shou ld be conducted with patients in a supine position.