Carpometacarpal joint

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 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 of the thumb (pollex), also known as the first carpometacarpal joint, or the trapeziometacarpal joint (TMC) because it connects the trapezium to the first metacarpal bone, plays an irreplaceable role in the normal functioning of the thumb. The most important joint connecting the wrist to the metacarpus, osteoarthritis of the TMC is a severely disabling condition; up to twenty times more common among elderly women than in average. Pronation-supination of the first metacarpal is especially important for the action of opposition. The movements of the first CMC are limited by the shape of the joint, by the capsulo-ligamentous complex surrounding the joint, and by the balance among involved muscles. If the first metacarpal fails to sit well 'on the saddle', for example because of hypoplasia, the first CMC joint tends to be subluxated (i.e. slightly displaced) towards the radius. The capsule is sufficiently slack to allow a wide range of movements and a distraction of roughly 3 mm, while reinforcing ligaments and tendons give stability to the joint. It is slightly thicker on its dorsal side than on the other. The first carpometacarpal joint is a frequent site of osteoarthritis in postmenopausal women. The description of the number and names of the ligaments of the first CMC varies considerably in anatomical literature. Imaeda et al. 1993 describe three intracapsular and two extracapsular ligaments to be most important in stabilizing the thumb: Early, anatomically correct drawings of the ligaments of the first carpometacarpal joints where produced by Weitbrecht 1742.