A tough ligament called the interosseous membrane prevents your forearm bones from splitting apart during heavy lifting.

The interosseous membrane (IOM) of the forearm is a complex fibrous tissue that spans the gap between the radius and the ulna. It consists of five distinct regions, with the central band being the most significant for structural integrity. This central band is roughly twice as thick as the other portions and provides the majority of the membrane's tensile strength.Research published in the Journal of Hand Surgery highlights that the IOM is responsible for transferring approximately 71% of the load from the radius to the ulna during weight-bearing activities. The fibers are oriented at a 20 to 25-degree angle, which is a specific biological design that converts longitudinal pressure into compressive force. This mechanism pulls the bones together rather than allowing them to shear apart under stress.Beyond load distribution, the IOM serves as a vital origin point for several deep muscles of the forearm, including the flexor pollicis longus and the extensor indicis. This increases the available surface area for muscle attachment without requiring larger or heavier bones. Clinical studies show that a tear in this membrane can lead to Essex-Lopresti injuries, where the radius migrates toward the elbow, causing severe joint instability.Biomechanical studies conducted at institutions like the Mayo Clinic have demonstrated that the membrane's stiffness is crucial for maintaining the distal radioulnar joint. Without this ligamentous support, simple tasks like rotating the wrist or performing a push-up would cause the forearm bones to diverge. This evolutionary adaptation allows humans to handle high-impact forces and perform complex manual tasks with precision and safety.