The extensor carpi ulnaris is a muscle within the superficial compartment of the posterior forearm. Its medial position within the forearm produces adduction as well as extension at the wrist. The tendon of the extensor carpi ulnaris passes through the 6th extensor compartment at the wrist. Attachments: Originates from the lateral epicondyle of the humerus, and posterior border of the ulna. It attaches to the base of fifth metacarpal. Actions: Extension and adduction of wrist. Innervation: Radial nerve (deep branch). Blood supply: Ulnar artery By TeachMeSeries Ltd (2025) Fig 1The muscles in the superficial layer of the posterior forearm. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Rate This Article