The Effect of Joint-Compressive Load and Quadriceps Muscle Force on Knee Motion in the Intact and Anterior Cruciate Ligament-Sectioned Knee

To determine the effect of an externally applied joint- compressive load and a quadriceps muscle force on knee motion, we tested nine intact cadaveric knees and four knees after sectioning of the anterior cruciate liga ment. Anteroposterior translation was measured at 0°, 15°, 30°, 45°, and 90° of knee flexion after the appli cation of an anteroposterior force of 100 N, a joint- compressive load of 0, 111, 222, 333, or 444 N, and a quadriceps force of 0 or 133 N. Both a joint-compressive load and a quadriceps force significantly decreased to tal anteroposterior translation by as much as 50% to 66% in intact knees and 42% to 71 % in anterior cruciate ligament-sectioned knees. A substantial anterior trans lation was also found with the application of a joint- compressive load or a quadriceps force and no anterior force. We termed this translation an anterior neutral- position shift. The anterior neutral-position shift was sig nificantly greater in the ligament-sectioned knees com pared with the intact knees, so much so that at flexion angles greater than 15°, the application of a 100-N pos terior force could not translate the tibia to the most an terior position achieved in the intact knee with a 100-N anterior force.