Flexor carpi ulnaris
Musculus flexor carpi ulnaris
Also known as: FCU
The most medial superficial flexor. It flexes and adducts (ulnar deviates) the wrist, and it is one of only "one and a half" forearm muscles supplied by the ulnar nerve.
Overview
FCU has a humeral head from the medial epicondyle and an ulnar head from the medial margin of the olecranon and the posterior border of the ulna (by an aponeurosis). The ulnar nerve enters the forearm between these two heads, beneath a fibrous arch (Osborne's ligament) that forms the roof of the cubital tunnel. The muscle descends along the ulnar border of the forearm to the pisiform (a sesamoid bone in its tendon) and continues as the pisohamate and pisometacarpal ligaments to the hook of the hamate and the base of the 5th metacarpal.
It is a powerful flexor and adductor (ulnar deviation) of the wrist. It stabilises the pisiform for abductor digiti minimi and is important in hammering and other forceful ulnar-sided movements. At the wrist, the ulnar artery and nerve lie just lateral to its tendon.
Anatomy
- Origin
Humeral head: medial epicondyle. Ulnar head: medial olecranon and posterior border of the ulna.
- Insertion
Pisiform, hook of the hamate (pisohamate ligament) and the base of the 5th metacarpal (pisometacarpal ligament).
- Action
Flexion and adduction of the wrist.
- Innervation
Ulnar nerve.
- Nerve roots
C7–C8 (T1)
- Arterial supply
Ulnar artery and its posterior ulnar recurrent branch.
- Relations
The ulnar nerve passes between its heads (cubital tunnel). At the wrist, the ulnar artery and nerve lie lateral to its tendon before entering Guyon's canal.
Function
- Flexes the wrist
- Adducts (ulnar deviates) the wrist
- Fixes the pisiform for abductor digiti minimi
Clinical significance
Cubital tunnel syndrome
Compression of the ulnar nerve under the FCU aponeurotic arch, made worse by prolonged elbow flexion. It causes paraesthesia in the 4th and 5th fingers, weakness of the intrinsic hand muscles, and a positive Tinel sign behind the medial epicondyle. It is the second commonest upper limb entrapment.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.