A sprain is an injury to a ligament – a soft tissue structure that connects two bones to one another around a joint. Sprains can vary in severity from partial tears of the ligament to complete tears. The most common site of injury in the thumb is the ulnar collateral ligament (UCL) of the metacarpal-phalangeal joint. Injuries to the other side of the thumb, the radial collateral ligament (RCL) can also occur, but are much less frequent (see image below).
Tears of the thumb UCL ligament occur when the thumb is jammed or forcibly bent away from the hand during a fall. A common cause is falling onto the hand while holding onto a ski pole – hence the term “skier’s thumb”. Alternatively, the ligament can slowly stretch out and wear out over time.
Swelling and bruising along the inside of the thumb are commonly seen following an injury. The thumb UCL acts as stabilizing band of tissue during pinching, holding a pen, opening doors or jars, or grasping a cup. When the thumb UCL is torn, pain and weakness are often felt during these activities.
X-rays are useful to evaluate for fractures or to see if a fragment of bone tore off with the ligament (Figure 2). Examination of the thumb is important to compare the stability (or laxity) of your injured thumb to your other side to determine the severity of the injury. MRI can be obtained, but is not usually necessary.
Incomplete tears associated with a stable joint can oftentimes be treated successfully in a splint
Complete tears may need to be treated surgically to restore stability to the joint and decrease pain, weakness and the risk of developing arthritis
Recent tears can usually be treated by repairing the ligament back to the bone
Chronic tears may require creating a new ligament from a tendon
If arthritis is present, a fusion of the joint may be the best option