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Anterior cruciate ligament (ACL) deficiency has been shown to alter the muscle function of the leg. This study aimed to investigate differences in force trace characteristics of a maximal isometric task between ACL deficient and uninjured knees. Six ACL injured and uninjured participants completed maximal adduction, extension, and flexion isometric contractions. Peak, mean, standard deviation (SD), coefficient of variance (CV), frequency and signal regularity were calculated for all trials. Mean flexion force was larger in the ACL intact (0.91 N/kg) compared to their deficient (0.67 N/kg; p<0.05) knee. SD, CV and frequency composition of the extension trial differed between limbs in the uninjured (p<0.05). Analysis of variability, frequency and regularity of a signal may provide information on the function of the knee.