BACKGROUND There are various tools and methods used for strength exercise. Elastic bands, one of the resistance exercise tools, have been used for various purposes, including muscle strengthening; however, there is very little evidence supporting their efficacy. The study was performed to investigate the effect of knee-ankle elastic bands on knee muscle strength-related parameters according to sex in healthy adults. MATERIAL AND METHODS This was a cross-sectional study. Twenty-one participants (11 female and 10 male) were studied using a cross-over design. Isokinetic concentric knee extension and flexion strength was measured at 60°/s and 180°/s with and without application of a therapeutic elastic band in the shape of an “8”, with knee flexion and ankle dorsiflexion. The variables related to muscle power automatically calculated in the protocol of the isokinetic system were compared according to sex and angular velocity. RESULTS Peak moment (PM), PM/body weight, average power, total work, and the agonist/antagonist ratio, demonstrated significant improvement (P<0.05) at both 60°/s and 180°/s "with" compared to "without" the elastic band according to sex. CONCLUSIONS The use of therapeutic elastic bands in the shape of a figure 8 with knee flexion and ankle dorsiflexion may be used as assistive devices for improving strength in muscles supporting the knee. Further high-quality studies are needed to assess the potential of elastic bands as assistive devices and not merely as exercise tools. Therapeutic elastic bands in the shape of an "8" with knee flexion and ankle dorsiflexion may be useful in sports activities.