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Collateral Ligament Injury (MCP Joints)
A jammed, sprained or twisted finger that stays swollen, tender or unstable may be more than a simple sprain. The collateral ligaments at the base of the fingers joints can be partly or completely torn, and a complete tear often needs treatment to avoid lasting instability.
What is it?
Each MCP joint has a collateral ligament on each side – radial and ulnar – that stabilises the joint against sideways force during grip and pinch. These ligaments are commonly injured by a jamming, twisting or side-on force. This is the same type of different joint and ligament as the ulnar collateral ligament of the thumb, which is the most common ligament injury affecting the MCP joints and is treated on its own page.
At a glance
What is it?
A sprain or tear of one of the paired ligaments that stabilise the side of a finger's MCP joint
Common symptoms
Pain and swelling at the side of the joint, tenderness over the ligament, and instability with side-to-side stress
Who it affects
People who jam or twist a finger during ball sports, a fall, or a work injury
Is it serious?
Mild sprains usually heal well; a complete tear or an unstable joint can lead to lasting instability or stiffness if untreated
Treatment options
Buddy taping or splinting for most injuries, or surgical repair or reconstruction for a complete tear or an unstable joint
First step
An examination to test joint stability, sometimes with an x-ray to exclude a fracture or bony avulsion
Causes and risk factors
- Jamming a finger catching a ball, such as in basketball, cricket or football
- A fall onto an outstretched hand
- A twisting injury to the finger
- A direct blow to the side of the finger
- Contact sports with a high risk of finger injury
Major ligament injuries at the MCP joint (at the knuckle) are not common but when they occur the diagnosis is often delayed by weeks to months. The ligament can tear mid-substance, or pull away from the bone it attaches to, sometimes taking a small fragment of bone with it (a bony avulsion).
Symptoms and how a collateral ligament injury presents
Pain, swelling and bruising develop at the side of the affected joint, with tenderness directly over the injured ligament. The joint is painful, and sometimes visibly unstable, when stressed from side to side. If the injury is not treated, the joint can remain stiff or unstable, and grip or pinch strength can be affected.
How is a collateral ligament injury diagnosed?
Diagnosis is based on examination, comparing the stability of the injured joint against the equivalent joint on your other hand, and testing pain and laxity with gentle side-to-side stress. An x-ray is usually taken to check for a fracture, a bony avulsion, or a joint that has shifted out of its normal position. An ultrasound assists in confirming the clinical diagnosis. Where the degree of injury to the ligament and associated structures is unclear an MRI may be performed, generally after specialist review of the patient, x-ray and ultrasound findings.
Treatment options for collateral ligament injury
Most sprains and partial tears are treated without surgery, using buddy taping or a splint and early protected movement to allow the ligament to heal. Surgery is considered for a complete tear with marked instability, a displaced bony avulsion fragment, or a joint that remains unstable or painful despite non-surgical treatment. For a chronic or neglected injury, the ligament may need to be reconstructed with a tendon graft rather than repaired directly.
When to see a hand surgeon
See a hand surgeon if the joint feels unstable, swelling and pain do not settle with buddy taping, there is visible deformity, or an x-ray shows a fracture or joint subluxation.
What to expect at your appointment
Our intake form asks you specific questions about your injury and how it happened. At your appointment, Dr Tomlinson will examine the joint, test its stability against the uninjured side, and review any imaging to decide whether splinting or surgery is the right treatment for you.
Related conditions and treatments
Collateral ligament injuries of the MCP joint are a similar injury to the ulnar collateral ligament rupture of the thumb (skier’s/gamekeeper’s thumb), which affects the thumb’s own MCP joint. A joint left unstable for a long period can go on to develop finger osteoarthritis over time.