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The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the interosseous margins of the
radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
and the
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
. It is the main part of the radio-ulnar
syndesmosis In anatomy, fibrous joints are joints connected by fibrous tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull the joints between the bones ar ...
, a fibrous joint between the two bones.


Function

The interosseous membrane divides the forearm into anterior and posterior compartments, serves as a site of attachment for muscles of the forearm, and transfers loads placed on the forearm. The interosseous membrane is designed to shift compressive loads (as in doing a hand-stand) from the distal radius to the proximal ulna. The fibers within the interosseous membrane are oriented obliquely so that when force is applied the fibers are drawn taut, shifting more of the load to the ulna. This reduces the wear and tear of placing the whole load on a single joint. The role of the membrane in load shifting is illustrated when the interosseous membrane is cut; the forces on each bone equalize from their natural proportions. Additionally, as the forearm moves from pronation to supination, the interosseous membrane fibers change from a relaxed state, to a tense state in the neutral position. They once again become relaxed as the forearm enters pronation. The interosseous membrane is composed of five ligaments: # - Central band (key portion to be reconstructed in case of injury) # - Accessory band # - Distal oblique bundle # - Proximal oblique cord # - Dorsal oblique accessory cord


Injury

Severe forearm injuries involving separation of the radius and ulna may be due to rupture of the interosseous membrane. Rupture can lead to proximal migration of the radius and an apparent lengthening of the ulna at the wrist. Often interosseous membrane tears are associated with adverse impacts on forearm rotation. MRI-assisted diagnosis has been used for mid-substance tears of the interosseous membrane but is expensive and not widely available. On the contrary, ultrasound has proven useful in diagnosing tears of the tibiofibular interosseous membrane of the leg, and this technique may also be applied to acute cases of membrane tears in the forearm due to its low cost and portability.


See also

*
Anterior interosseous nerve The anterior interosseous nerve (volar interosseous nerve) is a branch of the median nerve that supplies the deep muscles on the anterior of the forearm, except the ulnar (medial) half of the flexor digitorum profundus. Its nerve roots come from C8 ...
* Anterior interosseous artery *
Posterior interosseous nerve The posterior interosseous nerve (or dorsal interosseous nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared t ...
* Posterior interosseous artery *
Common interosseous artery The common interosseous artery, about 1 cm. in length, arises immediately below the tuberosity of the radius from the ulnar artery. Passing backward to the upper border of the interosseous membrane An interosseous membrane is a thick den ...
*
Recurrent interosseous artery The interosseous recurrent artery (or recurrent interosseous artery) is an artery of the forearm which arises from the posterior interosseous artery near its origin. It ascends to the interval between the lateral epicondyle and olecranon, on or t ...


References

Upper limb anatomy {{Musculoskeletal-stub