Gamekeeper's Thumb

The ulnar collateral ligament (UCL) of the thumb metacarpophalangeal (MCP) joint is injured by forced abduction, and treatment aims to restore a stable joint and pinch grip strength and to prevent chronic instability with CMC arthritis.

Two names. Skier's thumb is the acute, traumatic injury. Gamekeeper's thumb is the chronic, attritional one, named after Scottish gamekeepers who killed rabbits by wringing their necks and so loaded the thumb with repetitive valgus stress.

Who and how. It is a common sports injury, seen in skiing, rugby and AFL. The ski pole strap is the classically described mechanism; a fall on the outstretched thumb with forced abduction does the same.

The critical pathology is the Stener lesion, set out under Pathophysiology: the finding that makes surgery mandatory.

Two components, two positions. The UCL has a proper and an accessory part, and the position of the joint decides which is under tension. The proper collateral ligament (PCL) is dorsal and taut in flexion; it is the principal restraint to valgus stress at the MCP joint and the main stabiliser. The accessory collateral ligament (ACL) is volar, taut in extension, and blends with the volar plate, which also tightens in extension but is not a primary stabiliser.

The adductor aponeurosis. The adductor pollicis aponeurosis lies superficial to both components and over the UCL's insertion on the base of the proximal phalanx. In a complete tear the UCL stump can flip outside it.

Why the test position matters. Stressing the joint at 30° of flexion isolates the proper collateral ligament and relaxes the accessory ligament and volar plate, which makes it the more specific test for a UCL injury. Stressing in full extension tests the accessory UCL and volar plate as well.

Mechanism. Forced radial deviation (abduction) and hyperextension of the MCP joint load the UCL beyond its tensile limit. It fails most often at its distal insertion on the proximal phalanx, either as a midsubstance or avulsion tear of the soft tissue or as a bony avulsion of the ulnar base of the proximal phalanx. The ski-pole strap forcing the thumb sideways produces the acute injury; repetitive attritional valgus loading produces the chronic one.

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The Stener lesion. When the UCL avulses distally, the retracted free stump can flip and come to lie superficial to the aponeurosis while its bony footprint stays deep to it. The interposed aponeurosis physically separates ligament from bone, so the ligament cannot heal in continuity with cast treatment or immobilisation, and operative retrieval and repair are required. Stener described the interposition in 1962.

How often. A Stener lesion is quoted in approximately 80% of complete UCL ruptures. That figure comes from operative series, which are enriched for severe injury, so the true proportion among all complete ruptures, including those judged stable and never explored, is not known.

Associated injuries. A bony avulsion leaves a fragment at the base of the proximal phalanx, and a displaced avulsion often has a Stener lesion as well. Check the radial collateral ligament and the volar plate for a combined injury.

Natural history. A complete tear left untreated progresses to chronic instability, weak key pinch and eventual MCP osteoarthritis. The chronically unstable thumb shows a recognisable pattern:

• Unable to perform key pinch
• Compensatory MCP hyperextension
• CMC joint overload
• Progressive MCP arthritis

UCL injuries are graded on the stress examination: how far the joint opens, and whether it stops at a firm endpoint.

The complete tear. Any one of more than 30° of laxity, more than 15° of difference from the normal side, or the absence of a firm endpoint indicates a complete tear. A Stener lesion is likely in a Grade III injury.

History. Ask about the mechanism (a fall on the abducted thumb, a ski pole, a ball), the time since injury, weakness of pinch grip and previous injuries.

Inspection and palpation. Look for swelling and bruising over the ulnar side of the MCP joint. A palpable mass proximal to the joint is the Stener lesion felt clinically.

Stress testing. The examination is done in a fixed order:

1. Radiograph first. Stressing a non-displaced avulsion fracture can displace it, so rule out a bony avulsion before stressing the joint, and if a fracture is present do not stress test vigorously.
2. Test the normal side first, because laxity varies.
3. Apply valgus stress in 30° flexion for the proper UCL, then in full extension for the accessory UCL and volar plate.
4. Compare both the absolute laxity and the quality of the endpoint, soft or firm, with the normal thumb; more than 15° of asymmetry is significant.

Suspecting a Stener lesion. A palpable mass proximal to the joint together with significant laxity should raise the suspicion, and a suspected Stener lesion is confirmed with ultrasound or MRI.

Radiographs. AP, lateral and oblique views of the thumb in all cases. Look for an avulsion fracture at the base of the proximal phalanx and for subluxation or dislocation of the joint.

Stress radiographs. Valgus stress views, compared with the normal side, quantify the laxity as the degree of opening.

Ultrasound. Ultrasound confirms a Stener lesion and assesses the integrity of the ligament. It is dynamic, compares the two sides in real time and is cost-effective; it is operator dependent but effective. The pooled meta-analyses in the evidence section put its sensitivity for the Stener lesion at about 95% and support it as the first-line test, with MRI for equivocal scans.

MRI. MRI sensitivity for the Stener lesion is greater than 90%, and it shows the position of the ligament:

• Stener lesion: the UCL superficial to the adductor aponeurosis
• Complete tear: fluid between the ligament ends
• Avulsion: a bone fragment with the ligament attached

Radial collateral ligament (RCL) injury is the examiner's favourite contrast to gamekeeper's thumb, and checking the RCL is part of any thumb MCP examination - so it deserves setting out in its own right.

How common. RCL injuries are considerably less common than UCL injuries - most series report the ulnar side is injured several times more often, so the RCL accounts for only a minority of thumb MCP collateral injuries.

Mechanism and testing. The RCL fails with forced adduction (ulnar/varus deviation) of the thumb MCP joint - the mirror image of the abduction load that tears the UCL. It is assessed with varus (radial-deviation) stress in full extension and in 30° flexion, compared with the normal side; the same laxity thresholds and endpoint-quality principles used for the UCL apply.

The key anatomical contrast (why there is usually no "Stener" on the radial side). The adductor pollicis aponeurosis lies on the ulnar side, which is why a torn UCL can flip superficial to it and become trapped. On the radial side there is no equivalent broad aponeurosis reliably interposing, so a fixed Stener-type interposition is uncommon; a "reverse Stener" is described but is the exception, not the rule. Displacement blocking healing is therefore less characteristic of RCL tears, though complete tears still produce instability.

Deformity pattern - a clinical discriminator. Chronic RCL insufficiency produces volar and ulnar subluxation of the proximal phalanx with a dorsoradial prominence of the metacarpal head, and a supination/rotational deformity - a pattern distinct from the ulnar-sided instability of a UCL injury.

Management mirrors UCL principles: partial or stable injuries are immobilised; complete, displaced, or grossly unstable tears are repaired; chronic irreparable injuries are reconstructed (the Baek et al. figure-of-eight series on this page included 9 RCL reconstructions alongside 7 UCL) or treated by MCP arthrodesis if the joint is arthritic.

A swollen, painful thumb MCP joint after a fall has several mimics. The key is to distinguish UCL injury from radial-sided, bony, and joint pathology, because each changes management.

The grade of the injury and the presence of a Stener lesion decide treatment.

Non-operative. Grade I and II injuries without a Stener lesion, and non-displaced avulsion fractures, are immobilised and followed up with repeat stress testing.

Surgical indications.

• A Stener lesion, suspected clinically from a palpable lump with instability: an absolute indication
• Complete rupture without a firm endpoint (greater than 30° laxity)
• Displaced avulsion fracture
• Chronic instability

The complete tear without a Stener lesion. Complete tears are usually treated surgically because most have a Stener lesion, and conservative treatment of complete tears has a high failure rate. When imaging shows the stump is not displaced, practice varies and no randomised trial settles it (see Controversies).

Acute repair. The repair restores the ligament to its footprint:

1. Dorsoulnar, S-shaped incision.
2. Identify and protect the branches of the superficial radial (radial sensory) nerve, which run in the surgical field.
3. Find the stump superficial to the adductor and incise the adductor aponeurosis (hood) to retrieve it and reduce it back to bone.
4. Repair it to its footprint at the base of the proximal phalanx with a suture anchor (2.0-2.4mm, such as a Mitek anchor).
5. Close the aponeurosis if possible.

The chronic injury. Primary repair is not possible after 6 weeks. If the joint is not arthritic the ligament is reconstructed with a palmaris longus tendon graft in a figure-of-8 configuration through bone tunnels. If it is arthritic, the MCP joint is fused in 15-20° of flexion; silicone arthroplasty is rarely used.

Concept. A strong non-absorbable suture tape is anchored with knotless anchors spanning the repair, typically from the metacarpal head or neck to the ulnar base of the proximal phalanx, so that it lies alongside the reattached UCL. It acts as a load-sharing "internal brace" or ligament seat-belt that augments the primary anchor repair. It does not replace the native ligament, which still heals to its footprint.

Rationale. The tape carries part of the valgus load during healing, reducing repair-site gapping under early stress. The intended benefit is earlier protected mobilisation and faster return to sport or work than a repair left to heal in a cast, which matters for high-demand athletes.

Evidence status. Cadaveric biomechanical work suggests augmented constructs tolerate higher load with less gapping than suture-anchor repair alone, and early clinical case series report reliable stability with accelerated rehabilitation. There is, however, no high-quality randomised comparison against conventional anchor repair, and patient-reported superiority is unproven. In the viva, present it as an adjunct that may permit earlier motion, biomechanically supported but not yet proven superior to standard suture-anchor repair.

Cautions. The tape has limits and costs of its own:

• It must not be over-tensioned: an overconstrained MCP joint loses flexion and can stiffen.
• It adds implant cost and a second set of anchors.
• It is an adjunct, not a shortcut. A Stener lesion must still be reduced by releasing and repairing the adductor aponeurosis; augmentation over an unreduced stump does not restore anatomy.

Missed Stener lesion. This is the most important complication. It leads to chronic instability with a weak pinch grip and pain, and needs reconstruction or fusion.

After surgery. Complications of the repair, with their treatment:

• Radial sensory nerve injury, with neuroma, from the dissection: desensitisation or excision
• Stiffness from prolonged immobilisation: hand therapy
• Re-rupture
• Anchor failure

MCP arthritis. Chronic instability ends in MCP arthritis, which is fused if severe.

Rehabilitation. The protocol moves from protecting the repair to restoring motion and then strength:

• 0-6 weeks, protect the repair. Thumb spica cast or splint for 4-6 weeks, including the IP joint initially; elevation to reduce swelling; active finger range of motion.
• 6-10 weeks, restore motion. Transition to a removable splint, active range-of-motion exercises and hand therapy referral, avoiding stress on the repair.
• 10-12 weeks, strengthen. Progressive pinch strengthening, functional activities and return to light work.
• 12 weeks onwards. Return to sport and work, and full activity.

Return to sport. Contact sport resumes at 12-16 weeks and skiing at a minimum of 12 weeks, avoiding the pole strap initially; full activities resume at 16 weeks. A protective splint may be worn for sport at first, with the thumb buddy-taped to the index finger during the transition.

Acute repair. Acute repair gives a stable joint and strong pinch, and return to full function is expected; stiffness is the main concern.

Non-operative treatment. Appropriately selected Grade I-II injuries do well provided there is no Stener lesion. Undertreatment risks late instability.

Chronic reconstruction and fusion. Reconstruction is less predictable than acute repair and may leave some residual laxity. Fusion gives excellent pain relief at the cost of MCP motion.

Prognosis. Outcome depends on the time to surgery (acute does better than chronic), the presence of a Stener lesion, associated arthritis (fusion may be needed), and the patient's demands and compliance. The functional goals are a stable MCP joint, pinch strength 80% of the contralateral side, and pain-free function.

• Surgery vs immobilisation for complete tears without a confirmed Stener lesion. No RCT exists. Many surgeons trial cast immobilisation when imaging shows the stump is reduced (no Stener), reserving repair for failure; others repair all complete tears in high-demand patients to avoid chronic instability.
• Threshold laxity for "complete tear." Commonly quoted figures (greater than 30°, or 30-35° absolute, or greater than 15° side-to-side difference) vary between sources; endpoint quality (soft vs firm) is arguably more reliable than the absolute angle and should be assessed against the normal side.
• First-line imaging - ultrasound vs MRI. Meta-analytic data show ultrasound is highly accurate for Stener lesions and is increasingly the first-line test, but it is operator-dependent; MRI remains the fallback for equivocal scans.
• Management of small bony avulsions. Fragments too small to fix reliably (often quoted as under 3 mm or comminuted) are usually excised with suture-anchor repair of the ligament rather than ORIF; the size threshold for fixation is not standardised.
• Augmentation / internal brace. Suture-tape augmentation to allow earlier mobilisation is increasingly used, but high-level comparative evidence against conventional anchor repair is limited.

1. Stener B. Displacement of the ruptured ulnar collateral ligament of the metacarpophalangeal joint of the thumb. J Bone Joint Surg Br. 1962;44-B:869-879. (Landmark anatomical description - predates PubMed indexing.)
2. Tang P. Collateral ligament injuries of the thumb metacarpophalangeal joint. J Am Acad Orthop Surg. 2011;19(5):287-296. PMID 21536628. doi:10.5435/00124635-201105000-00006
3. Qamhawi Z, Shah K, Kiernan G, Furniss D, Teh J, Azzopardi C. Diagnostic accuracy of ultrasound and MRI in detecting Stener lesions of the thumb: systematic review and meta-analysis. J Hand Surg Eur Vol. 2021;46(9):946-953. PMID 33596684. doi:10.1177/1753193421993015
4. Raheman FJ, Rojoa DM, Dhingra M, Siddiqui S, Macdonald CR. The role of ultrasonography in the assessment of UCL injury of the thumb - a diagnostic test accuracy meta-analysis. J Plast Surg Hand Surg. 2020;55(2):83-95. PMID 33156740. doi:10.1080/2000656X.2020.1838295
5. Melville D, Jacobson JA, Haase S, Brandon C, Brigido MK, Fessell D. Ultrasound of displaced ulnar collateral ligament tears of the thumb: the Stener lesion revisited. Skeletal Radiol. 2012;42(5):667-673. PMID 23001117. doi:10.1007/s00256-012-1519-x
6. Baek JH, Lee JH, Ku KH. Novel figure-of-eight reconstruction with free tendon graft for unrepairable collateral ligament of the thumb MCP joint. Hand Surg Rehabil. 2024;43(3):101696. PMID 38657737. doi:10.1016/j.hansur.2024.101696
7. Başar H, Başar B, Kaplan T, Erol B, Tetik C. Comparison of results after surgical repair of acute and chronic ulnar collateral ligament injury of the thumb. Chir Main. 2014;33(6):384-389. PMID 25458468. doi:10.1016/j.main.2014.10.003