Metacarpophalangeal joint

The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers.^[1] These joints 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 proximal phalanges.^[1] Being condyloid, they allow the movements of flexion, extension, abduction, adduction and circumduction (see anatomical terms of motion) at the joint.^[1]

Metacarpophalangeal joint
The palmar aspect of the hand showing the epiphyses of the hand exploded. MCP joints in red.
The DIP, PIP and MCP joints of the hand: MetaCarpoPhalangeal joints, and the interphalangeal joints of the hand: Distal InterPhalangeal Proximal InterPhalangeal
Details
System	099
Identifiers
Latin	articulationes metacarpophalangeae
MeSH	D008662
TA98	A03.5.11.501
TA2	1835
FMA	35246
Anatomical terminology [edit on Wikidata]

Structure

Ligaments

Metacarpophalangeal articulation and articulations of digit. Palmar aspect.

Metacarpophalangeal articulation and articulations of digit. Ulnar aspect.

See also: Palmar plate

Each joint has:

• palmar ligaments of metacarpophalangeal articulations
• collateral ligaments of metacarpophalangeal articulations

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.

Function

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 while the fingers form a fist.^[2]

The muscles of flexion and extension are as follows:

Location	Flexion	Extension
fingers	Flexor digitorum superficialis and profundus, lumbricals, and interossei, assisted in the case of the little finger by the flexor digiti minimi brevis	extensor digitorum communis, extensor indicis proprius, and extensor digiti minimi muscle
thumb	flexor pollicis longus and brevis	extensor pollicis longus and brevis

Clinical significance

Arthritis of the MCP is a distinguishing feature of rheumatoid arthritis, as opposed to the distal interphalangeal joint in osteoarthritis.

Other animals

In many quadrupeds, particularly horses and other larger animals, the metacarpophalangeal joint is referred to as the "fetlock". This term is translated literally as "foot-lock". In fact, although the term fetlock does not specifically apply to other species' metacarpophalangeal joints (for instance, humans), the "second" or "mid-finger" knuckle of the human hand does anatomically correspond to the fetlock on larger quadrupeds. For lack of a better term, the shortened name may seem more practical.

See also

• Knuckle