Skier's Thumb (UCL Injury / Gamekeeper's Thumb)

What is it?

Forced radial abduction/hyperextension at thumb MCP tears the UCL. Complete tear may create Stener lesion (adductor aponeurosis interposition).

Commonly affected: Ulnar collateral ligament of thumb MCP

How it develops

1. Forced Radial AbductionThumb forced radially
2. UCL TearPartial or complete tear (usually distal)
3. Possible AvulsionAvulsion from proximal phalanx base (ulnar side)
4. Stener LesionTorn UCL displaces above adductor aponeurosis

Symptoms

• Ulnar thumb pain/swellingLocalized ulnar MCP pain, swelling, bruising
• Weak pinch/gripImpaired key/tip pinch
• Valgus stress painSevere with radial stress
• InstabilityRadial laxity on stress
• Palpable Stener massPalpable mass proximal to adductor aponeurosis

How it is examined

• Valgus stress testValgus stress at 0° and 30°; >35° or >15° side-to-side suggests complete tear
• Ulnar MCP tendernessPoint tenderness over UCL
• Pinch grip testAssess key/tip pinch weakness
• Stener lesion palpationSmall nodule palpable proximal to MCP

Imaging

AP thumb X-ray — avulsion at ulnar base of proximal phalanx; stress view helpful.

• Avulsion fragment at ulnar base of proximal phalanx (if bony)
• MCP radial deviation
• Asymmetric joint space on stress view
• Rule out fracture

MRI is modality of choice for UCL tear and Stener lesion.

• Full-thickness UCL tear
• Stener lesion (UCL displaced above adductor aponeurosis)
• Surrounding edema
• Avulsion fragment

When surgery is considered

Complete tear, Stener lesion, large displaced avulsion (>2mm), chronic instability

Procedures that may be discussed

• Primary UCL repair
• Suture anchor reattachment
• Bony avulsion fixation
• Tendon graft reconstruction (chronic)

Outlook

Partial tears do well with splinting; complete/Stener lesions need surgery.