Anatomy, Shoulder and Upper Limb, Forearm Nerves

The nerves of the forearm are complex due to the various nerve branches and the muscles that reside in the upper extremities. The forearm is composed of the radius bone laterally and the ulna bone medially. The four main joints of the forearm are the humeroulnar, humeroradial, and proximal and distal radioulnar joints. A fibrous syndesmosis joint connects the radius and ulna and divides the forearm into anterior flexor and posterior extensor compartments. Muscular components in the anterior compartment of the forearm are the pronator teres, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. Muscular components in the posterior compartment of the forearm are the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and supinator. The nerves in the forearm derive from branches of the brachial plexus and the medial antebrachial cutaneous nerve. The five branches of the brachial plexus are the musculocutaneous, axillary, median, ulnar, and radial nerves. All contribute to the innervation of the forearm except the axillary nerve. The branches from these four main nerves are the anterior interosseus, posterior interosseus, lateral cutaneous nerve of the forearm, deep branch of radial nerve, superficial branch of radial nerve, dorsal cutaneous branches of the ulnar and median nerves, and palmar cutaneous branches of the median and ulnar nerves.