A fall on an abducted thumb can tear an important ligament of the thumb MCP joint. Pain on the inner, or ulnar, side of the thumb should raise suspicion.
What is Gamekeeper's Thumb or Skier's Thumb?
Gamekeeper's thumb, also called Skier's thumb, is an injury to the ulnar collateral ligament (UCL) of the thumb at the metacarpophalangeal (MCP) joint.
The UCL is an important stabilizing ligament on the inner, or ulnar, side of the thumb MCP joint. It helps the thumb remain stable during pinching, gripping and grasping.
The injury can range from a partial tear to a complete tear. In some cases, the ligament pulls away with a small piece of bone, producing a bony avulsion injury.
Because the injury can sometimes look deceptively minor, a high index of suspicion is important, particularly when there is point tenderness on the inner side of the thumb MCP joint after an injury.
How does Gamekeeper's Thumb occur?
The typical mechanism is a sudden force that pushes the thumb outward, away from the hand.
It can occur when:
- A person falls on an outstretched hand with the thumb abducted or bent backward.
- A skier's thumb is forced outward while the hand is holding a ski pole.
- A sports injury suddenly forces the thumb away from the hand.
- There is a road-traffic accident or direct blow to the thumb.
- An occupational injury places excessive force on the thumb.
The mechanism of injury can sometimes be more informative than the external appearance. Significant swelling or bruising is not always present.
What are the symptoms?
Common symptoms include:
- Pain on the inner or ulnar side of the thumb MCP joint
- Point tenderness directly over the UCL
- Swelling around the thumb MCP joint
- Pain during gripping or pinching
- Weak pinch
- Difficulty using the thumb normally
- A feeling of instability or looseness
- Persistent pain after what initially appears to be a minor injury
The exact location of maximum tenderness is particularly important. Point tenderness directly over the UCL should raise suspicion of a UCL injury even when the initial X-ray appears normal.
Understanding the Anatomy
The two bones forming the thumb MCP joint are enclosed by a joint capsule.
At the sides of the joint, the capsule is reinforced by strong, localized thickened bands of tissue called the collateral ligaments.
On the inner, or ulnar, side is the ulnar collateral ligament (UCL). On the outer, or radial, side is the radial collateral ligament (RCL).
The important anatomical relationship can be understood in layers:
Bone → joint capsule → thickened collateral ligament → adductor pollicis more superficially → nerves → skin
This relationship becomes particularly important when understanding a Stener lesion.
What happens when the UCL tears?
The UCL can tear within its substance or pull away from its attachment, usually from the base of the proximal phalanx and less commonly from the metacarpal side.
The injury may be:
- Partial
- Complete
- Associated with a bony avulsion
The size and displacement of an avulsed bone fragment, the stability of the MCP joint and the condition of the ligament all influence treatment.
What is a Stener lesion?
A Stener lesion is an important form of UCL injury in which the torn ligament becomes displaced and moves superficial to the adductor pollicis aponeurosis.
In simple terms, the muscle comes to lie between the ligament and its normal attachment.
Once this happens, the ligament cannot easily return to its normal anatomical position and heal there. The overlying tissue acts as a barrier between the torn ligament and its attachment.
A Stener lesion is therefore an important finding when deciding treatment.
How is Gamekeeper's Thumb diagnosed?
Clinical examination comes first
The diagnosis begins with a careful history and clinical examination.
The hand surgeon will carefully assess the location of maximum tenderness, particularly whether there is point tenderness directly over the ulnar side of the thumb MCP joint, where the UCL is located.
The examination also assesses:
- Swelling and bruising
- Pain with thumb movement
- Pinch strength
- MCP joint stability
- Evidence of partial or complete ligament injury
Clinical suspicion remains paramount. Imaging is an important adjunct, not a substitute for a good clinical examination.
A good clinical examination should never be replaced by a normal imaging report.
Treat the patient, not merely the report.
At the same time, imaging and clinical examination should be viewed as complementary.
A good clinical examination and appropriate imaging are complementary, and the two should be interpreted together.
When the clinical findings and imaging do not appear to agree, it is appropriate to review the actual images and reassess the patient. In selected cases, discussion with the radiologist or sonologist, or further imaging, may help clarify the diagnosis.
The aim is not to question the imaging report, but to bring the clinical findings and imaging together to reach the correct diagnosis.
X-rays
Standard X-rays, usually including appropriate views of the thumb, can help identify:
- A bony avulsion
- A fracture fragment
- Displacement of a fragment
- Joint alignment abnormalities
- Other associated fractures
A normal X-ray does not rule out a UCL tear, because the ligament itself is not adequately visualized on a routine X-ray.
Stress Examination and Stress X-rays
A stress examination can provide valuable information about the stability of the thumb MCP joint and integrity of the UCL. It may demonstrate abnormal opening on the ulnar side when the thumb is gently stressed.
However, it must be performed judiciously, with the patient's informed consent and within the individual's tolerance for pain. Pain tolerance is highly individual.
The patient should be appropriately warned before the examination. If the patient is apprehensive or does not tolerate the examination, there should be no force whatsoever.
A painful examination should never be forced simply to obtain a positive stress finding.
A stress examination is therefore a useful clinical tool, but it must always be performed carefully, with appropriate explanation, consent and respect for the patient's comfort and safety.
Ultrasound
Ultrasound is a valuable adjunct in the assessment of thumb UCL injuries.
It can help demonstrate:
- Partial UCL tears
- Complete UCL tears
- Displacement of the torn ligament
- A Stener lesion
- Some associated bony avulsion injuries
- Dynamic instability in selected cases
Ultrasound can provide excellent information when performed with the appropriate technique and protocol by an experienced musculoskeletal sonologist.
However, ultrasound is operator dependent. Equipment, technique, protocol and experience can influence the examination.
A normal ultrasound report should therefore always be interpreted in the context of the clinical examination.
MRI
MRI provides detailed visualization of the soft tissues and can be particularly useful when:
- The clinical examination is inconclusive
- A complete tear is suspected
- A Stener lesion needs to be assessed
- A stress examination cannot be tolerated
- There is diagnostic uncertainty
- Associated injuries need evaluation
MRI has high diagnostic value for UCL injuries and can help distinguish displaced from nondisplaced ligament injuries.
As with all imaging, the quality of the study, appropriate protocol and interpretation are important.
When necessary, the actual MRI images should be reviewed together with the clinical findings rather than relying only on the written report.
Does every UCL injury require surgery?
No.
Not every UCL injury requires surgery.
A partial, stable tear can often be treated without surgery with appropriate immobilization and subsequent rehabilitation.
Complete unstable injuries, displaced tears, Stener lesions and significant avulsion injuries are more likely to require surgical treatment. However, the decision should be individualized according to the clinical findings, joint stability, nature of the injury and overall circumstances.
The important question is not simply whether the ligament is torn, but whether the thumb MCP joint is stable and whether the ligament can heal in an appropriate anatomical position.
How is surgery performed?
The primary objective of surgery is to restore the UCL to its anatomical attachment and restore MCP joint stability.
During surgery, the torn ligament is identified. If it has become displaced, it is released from its abnormal position and returned to its normal anatomical location.
The ligament is then secured to its anatomical footprint using an appropriate technique. Depending on the injury, this may involve:
- Direct suturing
- A suture anchor
- Transosseous fixation
- Other appropriate repair techniques
The surrounding tissues are restored appropriately.
The objective is not simply to close the tear. It is to restore the anatomical attachment, stability and conditions required for healing.
What if there is a bony avulsion?
A UCL injury can sometimes pull off a fragment of bone from its attachment.
Treatment depends on the:
- Size of the fragment
- Shape of the fragment
- Degree of displacement
- Stability of the joint
- Suitability of the fragment for fixation
A suitable displaced fragment may be reduced and fixed.
If the fragment is very small or unsuitable for fixation, the ligament can instead be repaired directly to its anatomical attachment using an appropriate technique.
The method of fixation is selected according to the individual injury rather than applying one technique to every bony avulsion.
Is a K-wire required in every UCL repair?
No.
A temporary K-wire across the thumb MCP joint is not necessary in every UCL repair.
In selected injuries, additional protection of the repair may provide greater security, particularly when there is concern about accidental loading, a fall or unexpected force during the early healing period.
The decision depends on factors such as the severity and stability of the injury, ligament or bone quality, associated bony injury and the surgeon's assessment.
It is an added safeguard, not a mandatory part of every repair.
When a K-wire is used, it is temporary and is removed according to the operative protocol after sufficient healing and protection of the repair.
How long does the thumb remain immobilized?
After treatment, the thumb is generally protected in a suitable cast or splint for 4 weeks, followed by rehabilitation.
If a K-wire has been used, its duration is determined separately according to the operative protocol and the stability of the repair.
What happens if a UCL injury is missed?
An untreated or inadequately treated UCL injury can result in:
- Persistent pain
- Weak pinch
- Difficulty gripping
- Chronic MCP joint instability
- Reduced thumb function
- Abnormal loading of the joint
- Progressive joint wear in longstanding cases
The thumb may continue to move, but its stability during pinch and grip can be compromised.
This is why persistent point tenderness on the ulnar side of the thumb MCP joint after an injury should not be ignored simply because the initial X-ray is normal.
Can a chronic UCL injury be treated?
Yes.
Chronic UCL injuries can be treated, although treatment can be more complex than treatment of an acute injury.
With time, the ligament may become scarred, shortened or unsuitable for direct repair.
When direct repair is not possible, ligament reconstruction, often using a tendon graft, may be required to restore stability.
The appropriate procedure depends on the duration of the injury, tissue quality, degree of instability, condition of the MCP joint and previous treatment.
Gamekeeper's Thumb vs Skier's Thumb
The terms Gamekeeper's thumb and Skier's thumb generally describe the same basic injury, the UCL injury of the thumb MCP joint.
The names have different historical associations, but clinically they refer to injury of the same important stabilizing ligament.
Why is the UCL so important?
The thumb is central to the function of the hand.
A stable UCL helps the thumb resist sideways forces during pinching, gripping and grasping.
Loss of UCL stability can therefore affect activities such as:
- Holding objects
- Turning keys
- Opening containers
- Writing
- Using tools
- Buttoning clothes
- Fine hand movements
The treatment goal is not merely to make the ligament appear healed. It is to restore a stable, functional thumb.
The Treatment Principle
The fundamental treatment principle is:
Restore the ligament to its anatomical attachment → restore MCP stability → protect healing → restore thumb function.
A stable thumb is essential for effective pinch and grip.