The interosseous membrane affects load distribution in the forearm

The role of the interosseous membrane in load sharing was defined by simultaneously quantitating loads in the distal radius and ulna and in the proximal radius and ulna with an axial load to the wrist, before and after transecting the interosseous membrane. With the interosseous membrane intact, the load at the proximal ulna was greater than at the distal ulna and the load at the proximal radius was less than at the distal radius, suggesting that force was transferred from the radius distally to the ulna proximally. The average percentage of the total load in each bone in supination was as follows: distal radius, 68%; distal ulna, 32%; proximal radius, 51%; proximal ulna, 49%. After interosseous membrane division, the proximal and distal load values became equal in each bone, in all forearm positions, demonstrating that without the membrane there was no load transfer between the radius and ulna. The interosseous membrane transfers load from the wrist to the proximal forearm, via fibers that run from the proximal radius to the distal ulna and exert a proximally directed pull on the ulnar shaft.