An articulation joint includes proximal links, distal links, and intermediate links connecting the proximal and distal links. The articulation joint has a straight configuration along a straight longitudinal axis, a first bent configuration when the articulation joint bends toward a first side of the longitudinal axis, and a second bent configuration when the articulation joint bends toward a second side of the longitudinal axis, opposite to the first side. When the articulation joint is in the straight configuration, a first gap is defined at the first side between adjacent proximal links, and the adjacent proximal links contact each other at the second side, a second gap is defined at each of the first side and the second side between adjacent distal links, and a third gap is defined at the first side between adjacent intermediate links, and adjacent intermediate links contact each other at the second side.