The interosseous membrane (IOM) links the ulna and the radius and acts as an extrinsic ligament, assisting the proximal radioulnar joint (PRUJ) and distal radioulnar joint (DRUJ) ligaments. It checks dissociating forces, transmits forces from one forearm bone to the other, and coordinates loading forces. The anterior plane of descending fibers from the radius checks the proximal displacement of this bone. Intermediate descending fibers are the strongest. The posterior plane, with ascending fibers from the radius, checks its proximal displacement. An early repair of a torn IOM is feasible and should be performed. This can be associated with an augmentation procedure.