Primary arc of thumb metacarpophalangeal (MCP) joint motion is flexion/extension with minor arcs of abduction/adduction and pronation/supination.

The thumb MCP joint has minimal intrinsic stability because of the large radius of curvature of proximal phalanx base.

Thumb MCP joint has radial and ulnar collateral ligaments, with each collateral ligament being composed of proper and accessory collateral ligament components.

Proper collateral ligaments originate from the condyles of the metacarpal head and travel obliquely to insert on the volar third of the proximal phalanx.

Proper collateral ligaments are tight in flexion and loose in extension.

Proper ulnar collateral ligament resists radial deviation of thumb in flexion.

Proper radial collateral ligament resists ulnar deviation of thumb in flexion.

Accessory collateral ligaments originate from an area on the metacarpal head volar to the proper collateral ligament origin and insert on the volar plate and sesamoids.

Accessory collateral ligaments are tight in extension and loose in flexion.

Accessory ulnar collateral ligament resists radial deviation of thumb in extension.

Accessory radial collateral ligament resists ulnar deviation of thumb in extension.

Floor of the joint is formed by the volar plate.

Dynamic stability is provided to the joint through tendinous attachments of the adductor pollicis, flexor pollicis brevis, and extensor pollicis brevis.

Acute injury because of sudden forced radial deviation (abduction) of the thumb.

Acute injury because of sudden forced ulnar deviation (adduction) of the thumb.

Chronic instability of the thumb MCP joint from inadequate treatment of an acute ligament tear or progressive attenuation of the ligament.

Ligament is commonly torn from the proximal phalanx and still attached to metacarpal. Rarely the ligament can tear proximally from the metacarpal.

The most common fracture pattern is an avulsion fracture from the base of the proximal phalanx where the ligament inserts.

Associated injuries can include tears of the dorsal capsule and ulnar aspect of the volar plate.

Acute injury is particularly common in skiers and ball-handling athletes. Falling while gripping the ski pole causes the handle to rapidly abduct the thumb.

Chronic injury is also called “gamekeeper’s thumb” because of attenuation of the collateral ligament from repetitive breaking of rabbit’s necks using the index finger and thumb.

Ulnar collateral ligament injury is more common than radial collateral ligament injury.

Fall onto an outstretched hand with the thumb abducted

Repetitive abduction activities at the thumb MCP joint

Difficulty with pinch or gripping with thumb and index finger

Pain worsened by forceful pinch or torsional motions of the hand such as unscrewing jar tops

Pain, tenderness, and ecchymosis at the ulnar or radial aspect of the thumb MCP joint

Physical examination is usually sufficient to make the diagnosis.

Inspect the resting posture of the thumb for volar subluxation or radial deviation of the MCP joint.

Pain with palpation of the ulnar or radial aspect of thumb MCP joint

Ecchymosis and swelling of the ulnar or radial aspect of thumb MCP joint

Weakness or pain with power pinch

Mass at ulnar aspect of thumb MCP joint may represent a Stener lesion.

Stener lesion—avulsed ligament with or without bony attachment displaced proximal and above the adductor aponeurosis such as that the aponeurosis prevents contact of the injured ligament with the avulsion site.

There is no potential mass from interposition on the radial side of the MCP joint comparable with the Stener lesion seen on the ulnar side.

With radial collateral ligament rupture, a dorsoradial prominence of the metacarpal head can be commonly seen.

Thumb MCP joint range of motion can be limited by pain.

Similar criteria to assess ulnar collateral ligament stability can be applied to the radial collateral ligament.

Must stress joint in extension and 30 degrees of flexion

Representative image(s)

Standard posteroanterior, lateral, and oblique radiographs of hand (Figure 10.1).

Inspect for volar subluxation of the MCP joint or radial deviation of the proximal phalanx.

Radiographs should be done prior to stressing the joint.

Rule out osteoarthritis if consideration is given to ligamentous reconstruction.