Interosseous

Interosseous is an anatomical term meaning between bones. It is used to describe structures that occupy or act between bones, such as membranes, ligaments, and intrinsic muscles.

Interosseous membranes are fibrous sheets connecting adjacent bones. The best known are the interosseous membrane between the radius and ulna in the forearm, and the membrane between the tibia and fibula in the leg. They maintain the distance between bones, stabilize the joints, provide attachments for muscles, and help transfer load from hand or foot to the forearm or leg. They permit limited, indirect movement and play a critical role in forearm rotation and leg stability.

Interosseous muscles of the hand comprise dorsal interossei (four) and palmar (plantar) interossei (three). Dorsal interossei originate from the adjacent sides of two metacarpals and insert on the bases of the proximal phalanges and extensor expansions; they abduct digits away from the middle finger. Palmar interossei originate from the sides of metacarpals 2, 4, and 5 and insert similarly; they adduct digits toward the middle finger. Both groups are innervated by the deep branch of the ulnar nerve and assist in fine motor control and grip.

Interosseous muscles of the foot include dorsal interossei and plantar interossei, which abduct and adduct toes, respectively, and are innervated by the lateral plantar nerve, a branch of the tibial nerve. These muscles contribute to toe alignment and balance during locomotion.

Clinical notes: injuries to interosseous structures, such as disruption of the interosseous membrane (for example in Essex-Lopresti injuries of the forearm), can impair load transmission and stability between bones.