Exoskeleton kinematic chain arranged to pivotally connect a first element to a second element, said first element comprising two pivot points A 1 and B 1 located at a distance A 1 B 1, said second element comprising two pivot points A 2 and B 2 located at a distance A 2 B 2, said exoskeleton kinematic chain comprising: - a first external link pivotally connected to said first element at said pivot point A 1; - a first end link pivotally connected to said first external link at a pivot point D 1, said pivot point D 1 being located at a distance A 1 D 1 from said pivot point A 1, said first external link and said first end link creating an angle D 1 ^ = θ and arranged to rotate with respect to each other about an axis x 1 passing through said pivot point D 1; - a second external link pivotally connected to said second element at said pivot point A 2; - a second end link pivotally connected to said second external link at a pivot point D 2, said pivot point D 2 being located at a distance A 2 D 2 from said pivot point A 2, said second external link and said second end link creating an angle D 2 ^ = D 1 ^ = θ and arranged to rotate with respect to each other about an axis x 2 parallel to said axis x 1 and passing through said pivot point D 2; - a first intermediate link pivotally connected to said first element at said pivot point B 1 and integrally connected to said second end link at a junction point C 2; - a second intermediate link pivotally connected to said second element at said pivot point B 2 and integrally connected to said first end link at a junction point C 1; said first and second end links (121,122) being pivotally connected to each other at a pivot point M, said pivot point M being located at a distance MB 1 from said pivot point B 1, at a distance MB 2 from said pivot point B 2, at a distance MD 1 from said pivot point D 1 and at a distance MD 2 from said pivot point D 2, wherein MB 1 = A 1 D 1, MD 1 = A 1 B 1 and MB 2 = A 2 D 2, MD 2 = A 2 B 2, said exoskeleton kinematic chain characterized in that, for any value of θ, the projections of said pivot points A 1, B 1, A 2, B 2 in a plane Π, orthogonal to said axes x 1 and x 2, lay in a circumference K, belonging to said plane Π, that has a center O and a radius r = A 1 D 1 = A 2 D 2 = D 1 S 2 = MB 2 = D 2 B 1 = MB 1, and in that said first element and said second element are arc-shaped with radius of curvature r and center of curvature O, in such a way that decreasing the value of θ said first and second element (101,102) rotate with respect to each other about an axis z orthogonal to said plane Π and passing through said center O in the direction for which said point A 1 is overlapped to said point B 2 and said point B 1 is overlapped to said point A 2. - a first external link pivotally connected to said first element at said pivot point A 1; - a first end link pivotally connected to said first external link at a pivot point D 1, said pivot point D 1 being located at a distance A 1 D 1 from said pivot point A 1, said first external link and said first end link creating an angle D 1 ^ = θ and arranged to rotate with respect to each other about an axis x 1 passing through said pivot point D 1; - a second external link pivotally connected to said second element at said pivot point A 2; - a second end link pivotally connected to said second external link at a pivot point D 2, said pivot point D 2 being located at a distance A 2 D 2 from said pivot point A 2, said second external link and said second end link creating an angle D 2 ^ = D 1 ^ = θ and arranged to rotate with respect to each other about an axis x 2 parallel to said axis x 1 and passing through said pivot point D 2; - a first intermediate link pivotally connected to said first element at said pivot point B 1 and integrally connected to said second end link at a junction point C 2; - a second intermediate link pivotally connected to said second element at said pivot point B 2 and integrally connected to said first end link at a junction point C 1;