The invention relates to a system to assist walking in spinal cord injured people, who preserve hip flexion capacity, comprising a pair of KAFO-type orthoses with: (a) an angular actuator (5) in each knee; (b) an orientation and acceleration sensor (6) on each leg; (c) a power supply and control system (7) to which all the sensors and actuators are connected; (d) a control algorithm deciding when to flex or extend the knee depending on the walking cycle, using information from the sensors.