The lower limb orthosis containing the rigid, non-deformable, at least bipartite casing consisting of the posterior part enclosing the back part of the calf and the bottom part of the foot and of the tibia part enclosing tibia and the upper part of the foot, both parts connected with self-attaching straps, connected in a detachable way with the casing, a pneumatic cuff located in the casing, and a pumping system connected to the pneumatic cuff with a hose in which the pumping system (4) is connected with the control module (10) monitoring the functioning of the z pumping system (4) and at least one pressure sensor (5).The method to control the pressure exerted by the orthosis on the limb consisting in that the limb is placed in the pneumatic cuff (3) of the ankle joint orthosis and closed in the non-deformable casing (1) and (2) with the self-attaching straps (8), after which the power supply of the pumping system (4) is switched on and the air is pumped by the pumping system (4) to the compartment of the pneumatic cuff (3) via the pressure sensor (5) in at least 10 sec cycles, and on exceeding the pressure of 25 mmHg it emits a warning signal, and on reaching the pressure of 29 mmHg the control module disconnects the power supply of the pumping system emits the continuous warning signal
