Saddle joint

A saddle joint (sellar joint,^[1][2] articulation by reciprocal reception^{[citation needed]}) is a type of synovial joint in which the opposing surfaces are reciprocally concave and convex. It is found in the thumb, the thorax, the middle ear, and the heel.

Saddle Joint
1: Ball and socket joint; 2: Condyloid joint (Ellipsoid); 3: Saddle joint; 4 Hinge joint; 5: Pivot joint;
Ligaments of wrist. Posterior view.
Details
Identifiers
Latin	articulatio sellaris
TA98	A03.0.00.048
TA2	1560
FMA	75298
Anatomical terminology [edit on Wikidata]

Structure

In a saddle joint, one bone surface is concave while another is convex.^[3][4] This creates significant stability.^[3]

Movements

The movements of saddle joints are similar to those of the condyloid joint and include flexion, extension, adduction, abduction, and circumduction.^[1] However, axial rotation is not allowed. Saddle joints are said to be biaxial,^[5] allowing movement in the sagittal and frontal planes.^[2]

Examples of saddle joints in the human body include the carpometacarpal joint of the thumb,^[6][7] the sternoclavicular joint of the thorax,^[8] the incudomalleolar joint of the middle ear,^[9] and the calcaneocuboid joint of the heel.^[2]

Name

The term "saddle" arises because the concave-convex bone interaction is compared to a horse rider riding a horse, with both bone surfaces being saddle-shaped.^[2][3] The saddle joint is also known as the sellar joint.^[1][2]