A differential spherical joint comprising a plurality of pulleys, a plurality of rotary motion transmission means connectable to respective actuators, and a plurality of tensioned flexible linear elements configured to transmit the motion between pulleys of said plurality of pulleys, wherein: - the plurality of pulleys comprises a first driving pulley and a second driving pulley arranged with the respective centers thereof at a predefined mutual distance along a first axis so that they can rotate independently of each other; - the plurality of rotary motion transmission means comprises a first transmission means connected to said first driving pulley as well as second transmission means connected to said second driving pulley so that said first axis is the axis with respect to which the first transmission means and the second transmission means transmit the respective rotary motion; - the plurality of pulleys further comprises a first driven pulley rotatable along a second axis perpendicular to said first axis; - said plurality of tensioned flexible linear elements comprises a first tensioned flexible linear element and a second tensioned flexible linear element which perform a complete revolution on said first driving pulley and on said second driving pulley, respectively, to then exit at each time in diametrically opposite points of the respective driving pulley (111, 112), wind about said first driven pulley, and return to said respective driving pulley (111, 112), thus forming a closed path; - the plurality of pulleys further comprises first four return pulleys (121, 122) on which said first and second tensioned flexible elements slide over about a quarter of revolution and go each time from the first or second driving pulley (111, 112) to the first driven pulley; - the first four return pulleys have rotation axes which are parallel - within a predefined tolerance angle - to said first axis; - the first four return pulleys are arranged on the side of said first driven pulley (113, 114) at the corners of a quadrilateral inscribing said first driven pulley; wherein there is provided a central body configured to house and support at least said first driven pulley and said return pulleys and to freely rotate about the first axis with respect to both said first and second driving pulleys; the joint being characterized in that: said first transmission means and said second transmission means are a first shaft and a second shaft arranged along said first axis, in particular said first shaft has a smaller diameter and is at least partially encircled by said second shaft having a larger diameter. - the plurality of pulleys comprises a first driving pulley and a second driving pulley arranged with the respective centers thereof at a predefined mutual distance along a first axis so that they can rotate independently of each other; - the plurality of rotary motion transmission means comprises a first transmission means connected to said first driving pulley as well as second transmission means connected to said second driving pulley so that said first axis is the axis with respect to which the first transmission means and the second transmission means transmit the respective rotary motion; - the plurality of pulleys further comprises a first driven pulley rotatable along a second axis perpendicular to said first axis; - said plurality of tensioned flexible linear elements comprises a first tensioned flexible linear element and a second tensioned flexible linear element which perform a complete revolution on said first driving pulley and on said second driving pulley, respectively, to then exit at each time in diametrically opposite points of the respective driving pulley (111, 112), wind about said first driven pulley, and return to said respective driving pulley (111, 112), thus forming a closed path; - the plurality of pulleys further comprises first four return pulleys (121, 122) on which said first and second tensioned flexible elements slide over about a quarter of revolution and go each time from the first or second driving pulley (111, 112) to the first driven pulley; - the first four return pulleys have rotation axes which are parallel - within a predefined tolerance angle - to said first axis; - the first four return pulleys are arranged on the side of said first driven pulley (113, 114) at the corners of a quadrilateral inscribing said first driven pulley; wherein there is provided a central body configured to house and support at least said first driven pulley and said return pulleys and to freely rotate about the first axis with respect to both said first and second driving pulleys; the joint being characterized in that: said first transmission means and said second transmission means are a first shaft and a second shaft arranged along said first axis, in particular said first shaft has a smaller diameter and is at least partially encircled by said second shaft having a larger diameter.