These joints taken together constitute the composite =articulatio
carpi=, or what is popularly termed the “knee-joint” in animals.[33]
This consists of three chief joints, viz., (1) The =radio-carpal joint=,
formed by the distal end of the radius and the proximal row of the
carpus; (2) the =intercarpal joint=, formed between the two rows of the
carpus; (3) the =carpo-metacarpal joint=, formed between the distal row
of the carpus and the proximal ends of the metacarpal bones. The
proximal and middle joints may be regarded as ginglymi, although they
are not typical or pure examples of hinge-joints. The distal joint is
arthrodial. In addition there are arthrodial joints formed between
adjacent bones of the same row (Articulationes interosseæ). All these
constitute a very composite joint, with numerous ligaments. The
articular surfaces have been described in the Osteology.
The =joint capsule= may be regarded, so far as the fibrous part is
concerned, as being common to all three joints. It is attached close to
the margin of the articular surface of the radius above and the
metacarpus below; its deep face is also attached to a considerable
extent to the carpal bones and to the small ligaments. Its anterior
part, the =dorsal= or =anterior common ligament=, is rather loose, and
assists in forming the fibrous canals for the extensor tendons. Its
posterior part, the =volar= or =posterior common ligament=, is very
thick and dense, and is closely attached to the carpal bones. It levels
up the irregularities of the skeleton here, and forms the smooth
anterior wall of the carpal canal. It is continued downward to form the
=subcarpal= or =inferior check ligament=, which blends with the tendon
of the flexor perforans about the middle of the metacarpus.
[Illustration: