This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Incudomalleolar joint is a ? 
Select and explain. 
A. Ellipsoid joint, B. Pivot joint, C. Hinge joint, D. Saddle joint
D: Saddle joint
Answer: D: Saddle joint 
Explanation: Synol joints are classified as follows :1) Plane synol joints (flat joints)2) Hinge joints (Ginglymus joints or ginglymi)3) Pivot or trochoid joints4) Condylar (bicondylar) joints5) Ellipsoid jointsNote : Metacarpophalangeal joints are ellipsoid joints functionally, but structurally they belong to condylar joints.6) Saddle (sellar) jointsThe aicular surfaces are reciprocally saddle shaped, i.e. concavo-convex. Examples are first (thumb) carpometacarpal joint, sternoclavicular joint, calcaneocuboid joint, incudomalleolar joint (smallest saddle joint) and patellofemoral joint.7) Ball and socket (spheroidal) joints