The interosseous membrane of forearm is a broad and thin plane of fibrous tissue descending obliquely downward and medialward, from the interosseous crest of the radius to that of the ulna; the lower part of the membrane is attached to the posterior of the two lines into which the interosseous crest of the radius divides.
It is deficient above, commencing about 2.5 cm. beneath the tuberosity of the radius; is broader in the middle than at either end; and presents an oval aperture a little above its lower margin for the passage of the volar interosseous vessels to the back of the forearm.
This membrane serves to connect the bones, and to increase the extent of surface for the attachment of the deep muscles.
Between its upper border and the oblique cord is a gap, through which the dorsal interosseous vessels pass.
Two or three fibrous bands are occasionally found on the dorsal surface of this membrane; they descend obliquely from the ulna toward the radius, and have consequently a direction contrary to that of the other fibers.
The membrane is in relation, in front, by its upper three-fourths, with the Flexor pollicis longus on the radial side, and with the Flexor digitorum profundus on the ulnar, lying in the interval between which are the volar interosseous vessels and nerve; by its lower fourth with the Pronator quadratus; behind, with the Supinator, Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis proprius; and, near the wrist, with the volar interosseous artery and dorsal interosseous nerve.