Skier’s thumb is an acute injury to the thumb joint, commonly resulting from a fall where the hand is subjected to sudden, excessive force. This trauma involves a sprain or tear of a ligament that stabilizes the thumb’s main joint. Although named for a common scenario in winter sports, this injury can occur during various activities that force the thumb away from the hand. Early recognition and proper treatment are necessary to avoid long-term weakness and instability.
The Anatomy of the Injury
The structure damaged in Skier’s Thumb is the Ulnar Collateral Ligament (UCL), located on the inside of the metacarpophalangeal (MCP) joint of the thumb. The MCP joint connects the thumb’s long bone (metacarpal) to the first bone (proximal phalanx). The UCL prevents the thumb from bending too far outward and stabilizes it during forceful gripping and pinching actions.
The injury typically occurs when the thumb is forced into hyperabduction, violently pushed away from the palm and index finger. In the classic skiing scenario, a skier falls while the thumb remains caught in the ski pole strap, or the pole acts as a lever. This mechanism subjects the UCL to extreme outward stress, causing it to stretch or tear.
This trauma results in varying degrees of damage, classified as a Grade 1 sprain (stretched ligament), a Grade 2 partial tear, or a Grade 3 complete rupture. Sometimes, the ligament pulls a small piece of bone away from its attachment point, known as an avulsion fracture. The severity of the damage directly influences the joint’s stability and the required treatment approach.
Identifying the Symptoms
The immediate aftermath involves sharp, localized pain and tenderness over the MCP joint at the base of the thumb, nearest the index finger. Swelling often develops quickly, and bruising may appear shortly after the trauma. Pain tends to worsen with any thumb movement, particularly when attempting to grasp or pinch objects.
The most concerning symptom is functional limitation, manifesting as noticeable weakness or instability when performing simple tasks, such as turning a doorknob. A complete UCL tear allows the thumb to move excessively outward when stressed, indicating the loss of stabilizing function. A partial tear often presents with more pronounced pain and tenderness than a complete rupture, which may feel less painful but shows significant joint laxity.
In instances of a complete ligament tear, a small, palpable lump may be felt on the inside of the thumb near the injury site. This bump signals a Stener lesion, a complication where the torn end of the ligament becomes displaced and trapped under nearby muscle tissue. This displacement prevents the ligament from healing naturally.
Diagnosis and Recovery Methods
Diagnosis involves a detailed physical examination and imaging studies. The physical assessment includes applying gentle outward pressure to the thumb, known as a valgus stress test. This test compares the stability and laxity of the injured joint to the uninjured one. Increased joint movement, especially greater than 15 to 20 degrees compared to the opposite thumb, suggests a significant tear.
Initial imaging involves X-rays to rule out associated fractures, such as an avulsion fracture. Since X-rays do not show soft tissues, an ultrasound or Magnetic Resonance Imaging (MRI) scan may be used. These scans visualize the ligament, confirm the degree of the tear, and check for a Stener lesion. This advanced imaging is important for planning the correct treatment strategy.
Treatment depends on the severity of the ligament damage. Non-surgical management is used for Grade 1 sprains and most Grade 2 partial tears where the joint remains stable. This involves immobilizing the thumb and wrist in a specialized splint or cast, often called a thumb spica, for four to six weeks. Rest and ice therapy are also recommended during this time.
Surgical intervention is required for complete ruptures (Grade 3 tears) and in all cases where a Stener lesion is identified. The displaced ligament in a Stener lesion cannot reconnect because the surrounding tissue creates a mechanical barrier. Surgery is necessary to reattach the ligament to the bone, often using a bone anchor. Physical therapy is initiated afterward to restore full range of motion, strength, and function.