Question: If passive radial deviation causes pain on the medial side of the wrist, what structure is likely to be injured?

Answer: The ulnar collateral ligament of the wrist.

The wrist joint is located at the junction where the bones at the base of the hand meet the two long forearm bones, the radius and the ulna. The small bones of the wrist are uniquely shaped and fit together like a jigsaw puzzle in two rows of four bones each. The row closest to the fingertips is called the distal row; the row nearest to the forearm is called the proximal row. These bones are joined to one another and to the radius and ulna by an intricate network of ligaments. The ligaments provide stability while allowing movement among the individual wrist bones and between the wrist and arm bones.

The ulnar collateral ligament of the wrist, also known as the internal lateral ligament, is a fibrous band of tissue located at the medial side of the wrist. (Be careful not to confuse it with the ulnar collateral ligament of the elbow, an entirely separate structure.) This ligament attaches at the styloid process of the distal ulna and inserts primarily on the triquetrum bone, with some fibers running to the pisiform and hamate bones. It functions to protect the wrist joint by limiting radial deviation (i.e., the side-bending movement of the wrist toward the thumb).

To assess the wrist for damage to the ulnar collateral ligament, grasp the forearm a few inches above the wrist with one hand and grip the medial part of the hand with the other. Stretch the ulnar side of the wrist by moving the hand laterally toward the thumb side, while stabilizing the arm with your other hand. Be sure the client's hand is relaxed. Note whether this produces discomfort at the medial side of the wrist. If it does, the ulnar collateral ligament is likely to be injured. (It is also possible for pain in this region to be caused by a fracture of the triquetrum bone or the styloid process of the ulna, so be sure your client sees a physician to rule out those conditions.)

Although injuries to the ulnar collateral ligament may occur throughout the ligament, they most commonly occur at the attachments - and primarily at the origin. To locate the ligament origin, place your thumb or index finger against the styloid process at the distal edge of the ulna. To locate the distal attachment, move distally to the attachments at the triquetrum and the pisiform bones.

The most common cause of ulnar collateral ligament injury is sudden or repeated trauma. Sudden trauma to the wrist often occurs when we try to protect ourselves by extending our hands to break a fall. Jobs or activities that require using the wrist in repetitive actions for many hours each day (long hours working on a computer, for example) make this area vulnerable to injury. Injuries also can result from performing the repetitive motions involved in playing an instrument without adequate rest and recovery.

Ulnar collateral ligament injury is common in karate students who practice hitting objects with the medial surface of the hand. It is also a frequent problem in massage therapists, drummers, carpenters, construction workers, house painters and athletes who use their wrists in stressful positions.