Systems, devices, and methods are disclosed for the purpose of quantitatively determining the susceptibility of a human subject to injure their Anterior Cruciate Ligament (ACL). A method for determining injury susceptibility scores or risk categories includes determining hip extension angles and knee varus angles during the performance of a stork test and determining hip abduction angles during a squat test. Determination of angles during certain movements may be achieved using various systems and devices, including wearable devices.