Metacarpophalangeal joint

The metacarpophalangeal joints  (MCP) are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint.

Ligaments
Each joint has a volar and two collateral ligaments.

Volar ligaments
The volar ligaments (glenoid ligaments of Cruveilhier; palmar or vaginal ligaments) are thick, dense, fibrocartilaginous structures, placed upon the volar surfaces of the joints in the intervals between the collateral ligaments, to which they are connected; they are loosely united to the metacarpal bones, but are very firmly attached to the bases of the first phalanges.

Their volar surfaces are intimately blended with the transverse metacarpal ligament, and present grooves for the passage of the Flexor tendons, the sheaths surrounding which are connected to the sides of the grooves.

Their deep surfaces form parts of the articular facets for the heads of the metacarpal bones, and are lined by synovial membranes.

Collateral Ligaments
The collateral ligaments (ligamenta collateralia; lateral ligaments) are strong, rounded cords, placed on the sides of the joints (Radial Collateral Ligament (RCL), Ulnar Collateral Ligament (UCL)); each is attached by one extremity to the posterior tubercle and adjacent depression on the side of the head of the metacarpal bone, and by the other to the contiguous extremity of the phalanx.

Dorsal surfaces
The dorsal surfaces of these joints are covered by the expansions of the Extensor tendons, together with some loose areolar tissue which connects the deep surfaces of the tendons to the bones.

Movements
The movements which occur in these joints are flexion, extension, adduction, abduction, and circumduction; the movements of abduction and adduction are very limited, and cannot be performed when the fingers are flexed.

The muscles of flexion and extension are as follows: