An exoskeletal kinematic chain arranged to assist the movement of a polyarticular bone chain , said polyarticular bone chain comprising: - an anatomical engagement portion ; - a number i of bone links , with 3 ≤ i < n , one of said bone links being integral to said anatomical engagement portion ; - a number j of anatomical rotational joints , with j = i - 1, each anatomical rotational joint arranged to allow a relative rotation θ j between two bone links adjacent to it; said exoskeletal kinematic chain comprising: - a frame integrally connected to said anatomical engagement portion ; - a number i of exoskeletal links , one of said exoskeletal links being integral to said frame ; - a number j of exoskeletal rotational joints , each exoskeletal rotational joint arranged to allow a relative rotation φ j between two exoskeletal links adjacent to it about a rotation axis x j ; each exoskeletal rotational joint located at a distance d j by the previous exoskeletal rotational joint along said exoskeletal kinematic chain , each distance d j being constant for each value of said relative rotations φ j ; each exoskeletal link being connected to a corresponding bone link by a kinematic constraint , each kinematic constraint arranged to allow the transmission of at least one force component F n orthogonal to said exoskeletal link and/or to said corresponding bone link , said exoskeletal kinematic chain characterized in that at each exoskeletal rotational joint is arranged a pulley arranged to rotate about a corresponding rotation axis x j , and in that at least one cable is provided substantially inextensible and integrally constrained to an exoskeletal link at the end of said exoskeletal kinematic chain opposite to said frame , said or each cable being in contact with each pulley . - an anatomical engagement portion ; - a number i of bone links , with 3 ≤ i < n , one of said bone links being integral to said anatomical engagement portion ; - a number j of anatomical rotational joints , with j = i - 1, each anatomical rotational joint arranged to allow a relative rotation θ j between two bone links adjacent to it; said exoskeletal kinematic chain comprising: - a frame integrally connected to said anatomical engagement portion ; - a number i of exoskeletal links , one of said exoskeletal links being integral to said frame ; - a number j of exoskeletal rotational joints , each exoskeletal rotational joint arranged to allow a relative rotation φ j between two exoskeletal links adjacent to it about a rotation axis x j ; - a frame integrally connected to said anatomical engagement portion ; - a number i of exoskeletal links , one of said exoskeletal links being integral to said frame ; - a number j of exoskeletal rotational joints , each exoskeletal rotational joint arranged to allow a relative rotation φ j between two exoskeletal links adjacent to it about a rotation axis x j ; each exoskeletal rotational joint located at a distance d j by the previous exoskeletal rotational joint along said exoskeletal kinematic chain , each distance d j being constant for each value of said relative rotations φ j ; each exoskeletal link being connected to a corresponding bone link by a kinematic constraint , each kinematic constraint arranged to allow the transmission of at least one force component F n orthogonal to said exoskeletal link and/or to said corresponding bone link , said exoskeletal kinematic chain characterized in that at each exoskeletal rotational joint is arranged a pulley arranged to rotate about a corresponding rotation axis x j , and in that at least one cable is provided substantially inextensible and integrally constrained to an exoskeletal link at the end of said exoskeletal kinematic chain opposite to said frame , said or each cable being in contact with each pulley . <EOS>