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The ulnar collateral ligament is a broad, triangular-shaped band made up of three parts: anterior, posterior, and oblique portions. Found in the elbow, wrist, and thumb, it provides stability for the joints against valgus or lateral stress. Other names for the ulnar collateral ligament include medial collateral ligament and internal lateral ligament.
In the elbow, the ulnar collateral ligament extends from the medial epicondyle of the humerus to the coronoid process and olecranon of the ulna — the humerus is the bone of the upper arm and the medial epicondyle is located at the bottom end of the humerus. Both the coronoid process and olecranon are located on the ulna and form the elbow joint along with the humerus. The ulnar collateral ligament is responsible for the stability of the elbow, and along with the triceps brachii, flexor carpi ulnaris, and the ulnar nerve make up a portion of the flexor digitorum superficialis, which is the muscle that flexes the fingers at the metacarpophalangeal joints.
The ulnar collateral ligament in the elbow can be subject to overuse injuries in throwing and racket sports. It is especially common in pitchers in baseball. Sometimes, surgery is necessary to repair the ligament and improve the stability of the joint. One type of surgical procedure is ulnar collateral ligament reconstruction, also called Tommy John surgery – named after the first baseball pitcher to have the procedure. The procedure involves using a tendon from the forearm to re-create the damaged ligament and support the elbow.
Ulnar collateral ligament can also refer to a ligament in the wrist. It is a rounded cord that attaches to the end of the styloid process of the ulna and divides at the other end into two fasciculi, or bundle of nerves. One of these attaches to the medial side of the triquetrum bone and the other to the pisiform and transverse carpal ligament.
This ligament can also be found in the thumb, running along the ulnar side of the metacarpophalangeal joint. The ligament is also subject to injury — it can become stretched or even torn, which is known as Gamekeeper’s thumb or skier’s thumb. Chronic injury to the ulnar collateral ligament in the thumb causes instability and loss of function. Most injuries that do not involve a complete tear of the ligament can be treated with immobilization in a splint. In cases where a complete tear is present, surgery is often necessary to repair the ligament.