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 or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

and the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

. It is the main part of the radio-ulnar

syndesmosis A syndesmosis (“fastened with a band”) is a type of fibrous joint in which two bones are united to each other by fibrous connective tissue. The gap between the bones may be narrow, with the bones joined by ligaments, or the gap may be wide a ...

, a

fibrous joint In anatomy, fibrous joints are joints connected by Fibrous connective tissue, 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 ...

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

5 ligaments of interosseous membrane of forearm

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.

References

Upper limb anatomy {{Musculoskeletal-stub

Function

Injury

See also

References