An apparatus and method of operation for measuring forces applied to a wearer's foot, the apparatus providing an indication to the wearer when forces on the foot exceed pre-selected upper limits or do not meet pre-selected lower limits. A body member is disclosed for attachment around the wearer's foot, the body member having an exterior sole and an interior sole portion covered by a rigid foot plate. The foot plate includes an upper support surface for contact with the foot. The interior sole portion includes at least one cavity within, with a force sensing unit attachable partially within the cavity. At least one strain gage is positioned at a midpoint on the force sensing unit, and the force sensing unit is connectable to the underside of the foot plate. An electronic means is mounted within the cavity and is electrically connected to the at least one strain gage. The electronic means receives electronic signals from the strain gage, the signals in proportion to force applied onto the force sensing unit when the wearer's foot applies weight onto the foot plate, with conversion of the signals to output signals for transmission to a signal processing means in a remotely located receiver and display unit. The display unit compares the output signals to upper limits and lower limits, and displays alarms when output signals do not reach lower limits, or exceed upper limits, therefore assisting with therapeutic rehabilitation of an injured lower extremity.