Saddle joint

An articulated joint ( the articulation sellaris ) is a joint that allows movement in two mutually perpendicular axes and thus has two degrees of freedom. The directions of movement are here a flexion / extension and abduction / adduction of the joint. In each case two joint surfaces are shaped like a riding saddle, and the convexity corresponds to a joint surface of the concavity of the other and vice versa.

An example is the root joint of the thumb ( carpometacarpal joint, trapezometacarpal joint of the thumb ) between the large trapezium and the first metacarpal bone. By combining the movements in both principal axes of the thumb circles is possible.

Also, the joint between the two ossicles Hammer ( Malleus ) and anvil ( incus ), the articulation incudomallearis, is a saddle joint.