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.