There are five Metacarpophalangeal joints in each hand, each of which is an ellipsoid joint. They joint is formed between the heads of metacarpal bones and proximal phalanges. All of the five metacarpophalangeal joints are strengthened by fibrous capsule.
Metacarpophalangeal Joint
Ligaments of metacarpophalangeal joints:
Ther are two collateral and one palmar ligament associated with each metacarpophalangeal joint.
- Palmar ligaments: These ligaments are a bit unusual. They are thick, dense and fibrocartilaginous. They are placed between the collateral ligaments and are connected to them. The palmar ligaments are attached firmly to the base of proximal phalanx, but the attachment to the head of metacarpal is loose.
- Collateral Ligaments: The collateral ligaments are strong, round cords which flank the joints. Each is attached to the posterior tubercle and adjacent pit on the side of its metacarpal head, and each passes distoanteriorly to the side of the anterior aspect of its phalangeal base.
Metacarpophalangeal Joint (Side view)
Blood supply of metacarpophalangeal joints:
These joints receive their blood supply form the dorsal and palmar metacarpal arteries., princeps pollicis artery and radialis indicis artery.
Nerve supply of metacarpophalangeal joints:
These joints recieve their nerve supply for the palmar digital branches of median nerve, the deep terminal branch of ulnar nerve and the posterior interosseous nerve.
Movements of metacarpophalangeal joints:
These joints are highly mobile showing varying degrees of flexion, extension, adduction, abduction and circumduction. Rotation is very limited and cannot take place alone, however, it may accompany flexion and extension.
Muscles producing movements:
- Flexion: Flexor digitorum superficialis, Flexor digitorum profundus, Lumbricals and Interossei. In the little finger, the flexor digiti minimi, and in the thumb, the flexor pollicis longus and flexor pollicis brevis also produce flexion.
- Extension: Extensor digitorum, extensor indicis (in index finger) and extensor digiti minimi (in little finger). In thumb the extensor pollicis longus and brevis produce extension.
- Abduction: Dorsal interossei, Long extensors, and abductor digiti minimi (in little finger). In thumb, the abduction is produced by abductor pollicis brevis and longus.
- Adduction: Palmar interossei and long flexors. In the thumb, adduction is produced by adductor pollicis.