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

The ulnar collateral ligament (UCL) of the thumb metacarpophalangeal (MCP) joint is one of the most commonly injured ligaments in the hand. A valgus force, directed radially, stretches or ruptures the UCL complex.

Two names for one ligament. "Gamekeeper's thumb" comes from Scottish gamekeepers, who broke the necks of rabbits and attenuated the UCL over time, so it names the chronic injury. The acute traumatic tear is now commonly called "skier's thumb", given its high incidence in skiing falls with the thumb in a pole strap.

The Stener lesion. In approximately 70% of complete tears the torn UCL displaces to lie superficial to the adductor pollicis aponeurosis, which then sits between the ligament and its insertion on the proximal phalanx. The ligament cannot heal to bone across it, even with prolonged immobilisation, so surgery is mandatory for complete functional recovery.

The joint. The thumb MCP is a condyloid (biaxial) joint. Flexion-extension is its primary motion, with abduction-adduction and rotation secondary, and it is less constrained than the finger MCP joints.

The UCL. It arises from the ulnar condyle of the metacarpal head and inserts on the volar-ulnar base of the proximal phalanx. It has two components, taut in opposite positions:

The volar plate attaches to the accessory collateral and provides additional stability.

The adductor aponeurosis. Adductor pollicis arises from the third metacarpal, capitate and trapezoid and inserts on the proximal phalanx at the ulnar sesamoid. Its aponeurosis lies superficial to the UCL insertion, which makes it central to the pathoanatomy of the Stener lesion.

Acute injury (skier's thumb). A forced valgus (radial deviation) stress, in any of these settings:

• A skiing fall with the thumb caught in the pole strap
• Ball-handling sports such as football and basketball, the thumb caught during a catch
• A fall onto the outstretched or abducted thumb
• Motor vehicle accidents
• Manual labour

Chronic injury (gamekeeper's thumb). Repetitive valgus stress, originally occupational in gamekeepers, attenuates the ligament gradually, and the instability is progressive.

How a Stener lesion forms.

1. Forced valgus stress ruptures the UCL, which tears from its insertion on the proximal phalanx.
2. The MCP joint subluxates briefly.
3. As the joint reduces, the ligament flips over the adductor aponeurosis.
4. The aponeurosis now lies between ligament and bone, and healing is impossible without surgical relocation.

The lesion is more frequent with greater initial displacement, and it cannot be definitively diagnosed clinically.

Clinical grade (Heyman). The grade comes from the stress test and guides the initial treatment.

Where the ligament tears.

• Distal avulsion from the proximal phalanx - most common
• Midsubstance tear within the ligament body
• Proximal avulsion from the metacarpal - less common

Is there a Stener lesion? If yes, surgery is mandatory. If no, consider conservative or surgical treatment. If uncertain, obtain an MRI or explore surgically. Location and the presence of a Stener lesion together determine the surgical approach.

Bony avulsion. Fragment size and displacement guide the fixation strategy:

• Non-displaced - may be treated conservatively
• Displaced greater than 2mm - consider ORIF
• Displaced into the joint - requires surgery
• Large fragment, greater than 20% of the articular surface - ORIF preferred

History. Pain at the ulnar aspect of the thumb MCP after one of the mechanisms above, with swelling over the thenar region. The patient notices weakness of pinch grip, a sense of instability in key pinch and difficulty with fine motor tasks.

Look and feel. Swelling at the ulnar MCP joint and ecchymosis over the ulnar thumb; an angular deformity may be visible in severe cases. The tenderness is over the UCL insertion at the volar-ulnar base of the proximal phalanx. A palpable mass at the ulnar MCP is the sign of a Stener lesion, the rolled-up ligament sitting superficial to the aponeurosis, and it is highly specific but not sensitive. Range of motion is usually full, limited by pain; compare with the contralateral side.

Stress testing. This is the critical examination.

1. Anaesthesia: local infiltration or a digital block if needed.
2. Stabilise the metacarpal firmly with one hand.
3. Test in extension: a radial-deviation (valgus) force applied to the proximal phalanx assesses the accessory collateral.
4. Test in 30° flexion: valgus stress assesses the proper collateral.
5. Evaluate both the degree of laxity, in degrees, and the quality of the endpoint, firm or soft.
6. Compare with the contralateral thumb, always.

Read the result against the Heyman grades. Laxity of greater than 30° absolute or greater than 15° more than the other thumb indicates a complete tear, as does the absence of a firm endpoint, and with no firm endpoint a Stener lesion is likely.

Pinch and function. Key pinch, thumb against the side of the index finger, is reduced with UCL insufficiency; compare with the other side. The functional assessment covers writing, buttoning, turning a key and opening a jar.

Differential diagnosis. Several conditions mimic an ulnar-sided thumb injury, and the common trap is to attribute all base-of-thumb pain to a UCL tear.

Radiographs. Three views of the thumb:

• PA - shows a bony avulsion if present
• Lateral - subluxation
• Oblique - additional view of the fragment

Look for a bony avulsion fragment at the base of the proximal phalanx, a proximally displaced fragment (a radiographic sign of a Stener lesion), and subluxation, the proximal phalanx radially deviated on the metacarpal.

Stress radiographs are controversial. Some advocate them, but they risk displacing a partial tear, and MRI is preferred if the diagnosis is uncertain.

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MRI. The indications:

• Equivocal clinical examination
• Identifying a Stener lesion preoperatively
• Assessing associated injuries
• Differentiating a partial from a complete tear

Reading the MRI. The normal UCL is low signal on all sequences, with a smooth contour from metacarpal to proximal phalanx. A partial tear shows thickening and increased signal within a ligament whose continuity is maintained. A complete tear with a Stener lesion shows a discontinuous UCL displaced proximally and superficially, the "yo-yo on a string" appearance, with the adductor aponeurosis visibly interposed.

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Ultrasound. A dynamic study that can visualise the stress test, cost-effective and free of radiation, and becoming more popular. It identifies the displaced ligament and can visualise a Stener lesion, but it is operator-dependent.

CT has a limited role, mainly for complex avulsion fractures and for planning ORIF, with 3D reconstruction to assess the fragment.

The decision. The grade, the presence of a Stener lesion, any bony fragment and the time since injury settle each scenario below.

Algorithm

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Setup. Supine, the arm on a hand table and a tourniquet on the upper arm. General anaesthesia or a regional block (axillary or supraclavicular), often with local infiltration added. The kit is 2.0-2.4mm suture anchors, typically one or two, or the equipment for transosseous sutures, with fine hand instruments and loupe magnification at 2.5-3.5x.

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Early.

• Wound - infection (rare), haematoma, dehiscence
• Nerve injury - the dorsal sensory branches of the radial nerve, with numbness over the dorsal thumb; usually a neurapraxia that recovers
• Fixation failure - suture anchor pull-out or refracture of the avulsion fragment; may need revision

Late.

• Chronic instability - the most significant complication, from a missed Stener lesion or an inadequate repair; may need reconstruction
• Stiffness - common after prolonged immobilisation; hand therapy is essential, and it usually resolves with time
• Post-traumatic arthritis - uncommon with anatomical repair, more common after chronic instability; may need arthrodesis
• Persistent weakness - a pinch strength deficit that usually improves over 6-12 months and may be permanent in chronic cases
• Cold intolerance - common in the first year, usually improving with time

Days 0-14. The rigid thumb spica splint is maintained full-time and kept clean and dry, with elevation above heart level for the first 48-72 hours and ice packs around the splint without getting it wet. The first dressing change at 48-72 hours inspects for haematoma and infection, and the sutures come out at 10-14 days.

Analgesia. Expect moderate pain for the first 24-48 hours.

• Paracetamol 1g four times daily
• Ibuprofen 400mg three times daily, if there are no contraindications
• A short course of opioids if needed, 3-5 days maximum

What to watch for. Excessive pain raises concern for compartment syndrome, which is rare. Increasing pain, fever or drainage suggest infection. Numbness in the radial nerve distribution is expected and is monitored.

Weeks 2-6: protected immobilisation. The spica stays on full-time with the MCP in 20-30° flexion; it may convert to a removable splint at week 4, at the surgeon's preference, and from weeks 4-6 it is removable but taken off only for gentle washing. The IP joint remains free, with active IP flexion and extension encouraged; adjacent finger range-of-motion exercises are added in weeks 2-4, and the IP joint exercises continue through weeks 4-6. The repair takes no stress, though very gentle active motion may begin at 4-6 weeks if the surgeon permits. No lifting, gripping, pinching or driving. Showering needs a waterproof cover, and desk work is acceptable with the splint on.

Weeks 6-8: early mobilisation. The splint comes off 3-4 times daily for gentle active MCP flexion and extension, therapist-supervised if possible, and is worn part-time between sessions, at night and for any potentially stressful activity. No passive stretching and no valgus stress.

• Thumb opposition to each fingertip
• Gentle fist making (light grip)
• Tabletop slide exercises
• Tendon gliding exercises

Light daily activities, computer work and writing are allowed; sport and heavy lifting are not.

Weeks 8-12: strengthening. Grip activity increases gradually, with putty progressing from soft to medium to firm and pinch strengthening (key, tip and lateral pinch), resistance advancing as tolerated. The goals are full active range of motion, MCP flexion of 50-60°, and extension to neutral or near-neutral, with no extension lag acceptable. Work- and sport-specific tasks are simulated with a graded return to daily tasks; taping may support the thumb during activities, and the splint is worn at night only. Most daily activities, light recreation and a gradual return to manual work resume, but not contact sport.

Week 12 onward: return to sport. The criteria:

• Pain-free range of motion
• Strength at least 80% of the contralateral side
• No instability on stress testing
• Patient confidence in stability
• Surgeon clearance

A gradual return-to-sport protocol follows, with position-specific training for athletes and possibly protective taping or a brace initially; the splint is used as needed for sport. Full clearance usually comes 3-4 months after surgery. Strength may continue improving for up to 12 months; review annually in the first year and monitor for late instability or arthritis.

Red flags needing immediate review.

• Sudden increase in pain
• Loss of motion after initial gains
• Recurrent sensation of instability
• Signs of infection
• Persistent weakness at 3 months
• Donor site problems, if a graft was used

Acute repair. Return to full activities is 85-90%, and patient satisfaction is greater than 90%.

What predicts success. Early recognition and treatment, with under 3 weeks optimal; accurate diagnosis of the Stener lesion; a secure anatomical repair; a protected rehabilitation protocol; and patient compliance with the restrictions.

Chronic reconstruction. Return to the previous level of activity is 60-70%. Mild instability may persist, a slight loss of motion (a 10-15° MCP flexion deficit) is common, and there is occasional weather-related discomfort.

Conservative treatment. For appropriate indications, partial tears without a Stener lesion, success is 85-90%, and full recovery, including full strength, is expected with compliant immobilisation. The 10-15% that fail may have had a missed Stener lesion. Failure is predicted by:

• Initial laxity greater than 25°, even if less than 30°
• A soft or absent endpoint
• A palpable mass suggesting a Stener lesion
• A high-demand occupation or sport

Return to sport depends on the sport.

The overall reinjury rate is 5-10%, higher in contact sports (10-15%) and reduced by protective taping or bracing; most reinjuries occur in the first year.

Long term, beyond 5 years. Post-traumatic MCP arthritis develops in 10-20% at 10 years, with a higher risk after an intra-articular fracture component, chronic instability before treatment, or diagnosis delayed beyond 6 weeks. Mild weather-related discomfort persists in 20-30% and cold intolerance in 15-20%; persistent radial nerve numbness is rare (5-10%), and clinically significant instability affects less than 5% after proper repair. The overall revision rate is less than 10%, most commonly for persistent instability, with reconstruction or arthrodesis as salvage.

Counselling. Full recovery takes 4-6 months at minimum. Mild aching in cold weather may persist long term, and a small area of numbness is common but usually improves. Excellent stability is expected with proper treatment, and the arthritis risk is present but low. Protective taping may be needed for high-risk sports; avoid activities that stress the thumb into valgus in the first year, return to full activity gradually, and listen to symptoms during the return to sport.

Guidelines, Registries and Global Practice

Global Epidemiology

The thumb UCL is the most frequently injured ligament at the base of the thumb. A 2025 systematic review reported that UCL injuries account for approximately 86% of all base-of-thumb injuries (Assefa 2025, PMID 40741552). Acute "skier's thumb" remains one of the commonest upper-limb injuries in alpine sports, while ball-handling and contact sports (AFL, rugby codes, basketball, American football) generate a year-round burden. The Stener lesion complicates a substantial proportion of complete tears; modern radiographic series put the displaced-fleck (high-grade) subgroup at around 7.5% of all UCL presentations (Daryoush 2025, PMID 39831878).

Guideline and Society Positions (Side-by-Side)

There is no single high-level clinical-practice guideline (CPG) specific to thumb UCL injury; practice is driven by hand-society consensus and systematic-review evidence. The table summarises the prevailing position of major bodies.

Registry and High-Level Evidence

Thumb UCL repair is a soft-tissue procedure and is not captured by arthroplasty joint registries (AOANJRR / NJR / AJRR), so registry survivorship data do not exist. The best population-level evidence is therefore from pooled systematic reviews:

Practice Variation

International practice varies chiefly in first-line imaging (ultrasound-led in many UK/European hand units versus MRI in many North American centres) and in fixation choice (transition from transosseous sutures to suture anchors, and now suture-tape internal-brace augmentation enabling earlier motion). The threshold for surgery is more consistent: complete tear with a Stener lesion, gross instability, no firm endpoint, or a displaced bony avulsion.

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Evidence Base