Systems and methods for constructing custom orthotics are described. Several embodiments of the system use sensor pads to obtain both static and dynamic three dimensional information concerning the shape or topography of the bottom surface of a patient's foot. The information is analyzed to obtain information useful in constructing a custom orthotic from a selection of basic orthotic shells. Once constructed, the orthotic can modify a patient's gait. One embodiment of the present invention includes a user terminal including a sensor pad connected to a computer, a server configured to analyze three dimensional information acquired by the sensor pad, a manufacturing terminal configured to display the results of the server's analysis of the three dimensional information and a network that connects the user terminal to the server and the server to the manufacturing terminal.