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The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones.. The CMC joint of the thumb or the first CMC joint, also known as the trapeziometacarpal (TMC) joint, differs significantly from the other four CMC joints and is therefore described separately.
The carpometacarpal joint connects the carpal bones to the metacarpus or metacarpal bones which are joined at the intermetacarpal articulations. In the fingers, finally, are the metacarpophalangeal joints (including the knuckles ) between the metacarpal bones and the phalanges or finger bones which are interconnected by the interphalangeal joints .
The TMC joint is a synovial joint between the trapezium bone of the wrist and the metacarpal bone at the base of the thumb. This joint is a so-called saddle joint (articulatio sellaris), unlike the CMC joints of the other four fingers which are ellipsoid joints. [17] This means that the surfaces of the TMC joint are both concave and convex.
Joints of the hand, X-ray. The bones in each carpal row interlock with each other and each row can therefore be considered a single joint. In the proximal row a limited degree of mobility is possible, but the bones of the distal row are connected to each other and to the metacarpal bones by strong ligaments that make this row and the metacarpus a functional entity.
Carpometacarpal bossing (or metacarpal/carpal bossing) is a small, immovable mass of bone on the back of the wrist. The mass occurs in one of the joints between the carpus and metacarpus of the hand , called the carpometacarpal joints , where a small immovable protuberance [ 1 ] occurs when this joint becomes swollen or bossed.
The first metacarpal bone is short and thick with a shaft thicker and broader than those of the other metacarpal bones. Its narrow shaft connects its widened base and rounded head; the former consisting of a thick cortical bone surrounding the open medullary canal; the latter two consisting of cancellous bone surrounded by a thin cortical shell.
The synovial membrane for these joints is continuous with that of the carpometacarpal joints. Additional images. The bones in the hand.
Besides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows: the first with the trapezium ; the second with the trapezium, trapezoid , capitate and third metacarpal;