Lumbar corset consisting of a band which can be opened, made by joining two permanently joined half-parts (12, 14), at the respective distal ends (16, 18), by means of a joining member, the respective proximal ends (22, 24) of said two half-parts (12, 14) being instead designed to overlap each other and be joined in the lumbar corset closed configuration, said lumbar corset being provided with a closing system consisting of an assembly made of straps applied on the outer side of said lumbar corset and comprising: - at least a first dorsal strap, constrained to the distal end of a first half-part at a first upper constraint point and at a first lower constraint point, wherein said first dorsal strap extends longitudinally towards the proximal end of the second half-part in order to wrap around a first free pulley; - at least a second dorsal strap, constrained to the distal end of the second half-part at a second upper constraint point and at a second lower constraint point, wherein said second dorsal strap extends longitudinally towards the proximal end of the first half-part in order to wrap around a second free pulley; - a first primary side strap, operatively connected to the second dorsal strap through said second pulley which is free and made integral with the first half-part at a first predefined fixing point (44; 80); and - a second primary side strap, operatively connected to the first dorsal strap through said first pulley which is free and made integral with the second half-part at a second predefined fixing point (48; 84), wherein both primary side straps (42, 46) are provided, at their respective free ends, with respective releasable anchoring means (50, 52), which can be coupled with respective anchoring portions (54, 56) provided at said proximal ends (22, 24), characterized in that the first primary side strap is operatively connected to the corresponding second dorsal strap by interposing, in addition to said second free pulley, a first mobile pulley and a first secondary side strap, said first secondary side strap being made integral with the first half-part at a first predefined fixing point, and in that the second primary side strap is operatively connected to the corresponding first dorsal strap by interposing, in addition to said first free pulley, a second mobile pulley and a second secondary side strap, said second secondary side strap being made integral with the second half-part at a second predefined fixing point, and in that said second free pulley and said first mobile pulley of the first half-part, as well as said first free pulley and said second mobile pulley of the second half-part, are arranged along a same axis which is parallel to the longitudinal development direction of the openable band forming the lumbar corset. - at least a first dorsal strap, constrained to the distal end of a first half-part at a first upper constraint point and at a first lower constraint point, wherein said first dorsal strap extends longitudinally towards the proximal end of the second half-part in order to wrap around a first free pulley; - at least a second dorsal strap, constrained to the distal end of the second half-part at a second upper constraint point and at a second lower constraint point, wherein said second dorsal strap extends longitudinally towards the proximal end of the first half-part in order to wrap around a second free pulley; - a first primary side strap, operatively connected to the second dorsal strap through said second pulley which is free and made integral with the first half-part at a first predefined fixing point (44; 80); and - a second primary side strap, operatively connected to the first dorsal strap through said first pulley which is free and made integral with the second half-part at a second predefined fixing point (48; 84),