Knee adduction moment of an untethered human during gait is modulated by determining at least one feature associated with instantaneous knee adduction moment of the untethered human during a gait cycle. Feedback to be transmitted to the human is, optionally, derived from the feature, such as by comparing the at least one feature to a value, such as a target value. The feature, or feedback derived from the feature, is transmitted to the human for response by the human, thereby modulating knee adduction moment of the untethered human during the gait.