Scapholunate Dissociation

Overview

Scapholunate dissociation is an injury to the scapholunate ligament, a strong band of tissue that links two small wrist bones, the scaphoid and the lunate. This ligament keeps the bones moving together in a coordinated way. When it tears, the two bones can drift apart and the wrist loses its normal stability and mechanics.

This injury usually follows a fall onto an outstretched hand, the same mechanism that causes many wrist fractures, and the two injuries sometimes occur together. Scapholunate dissociation is significant because it can be easy to miss at first and, if left untreated, can lead to a predictable pattern of wrist arthritis over time. Recognizing and treating it early, while the ligament can still be repaired and the bones realigned, offers the best chance of preserving wrist function and preventing long-term damage.

Symptoms

Symptoms can be subtle, especially early on, and may be mistaken for a simple sprain:

• Pain on the back of the wrist, often toward the thumb side
• Swelling over the wrist
• Tenderness in the area between the scaphoid and lunate
• A clicking, clunking, or popping sensation with wrist movement
• Weakness of grip
• Pain that worsens with loading the wrist, such as pushing up from a chair
• A feeling of instability or that the wrist gives way

Because pain may be moderate and X-rays can look normal at first, persistent wrist pain after a fall should be evaluated rather than dismissed as a sprain.

Causes

Scapholunate dissociation is caused by force that tears the ligament between the scaphoid and lunate:

• Fall onto an outstretched hand: The most common cause, especially with the wrist bent back, which stresses the ligament.
• Sports injuries: Falls and impacts in activities such as skating, cycling, gymnastics, and contact sports.
• High-energy trauma: Car crashes and falls from height, sometimes alongside fractures or dislocations.
• Repetitive or degenerative changes: Less commonly, gradual weakening of the ligament over time, which can occur with certain types of arthritis.

Risk Factors

• Participation in sports with a high risk of falls or wrist impact
• Activities or jobs that load the wrist heavily
• A previous wrist injury or fracture
• Inflammatory arthritis affecting the wrist ligaments
• Younger, active adults, in whom this injury is common

Diagnosis

Diagnosis can be challenging and often requires specific tests:

• Physical exam: Checking for tenderness over the scapholunate area and performing maneuvers that test for instability and reproduce a click.
• X-rays: Standard and sometimes stress (clenched-fist) views, which may reveal a gap between the scaphoid and lunate. Comparing both wrists can help.
• MRI: Can show ligament tears that are not visible on X-ray.
• Wrist arthroscopy: A minimally invasive look inside the joint, considered the most accurate way to assess the ligament and the degree of injury.

Treatment

Treatment depends on how recent the injury is, the extent of the ligament tear, and whether the bones have shifted or arthritis has developed:

• Immobilization: Partial tears or very early injuries may be treated with a cast or splint and therapy.
• Surgical repair: A complete, recent tear is often best treated by surgically repairing the ligament and realigning the bones, sometimes with pins to hold them while healing.
• Reconstruction: If the injury is older and the ligament cannot be repaired directly, surgeons may reconstruct it using nearby tissue.
• Salvage procedures: When arthritis has already set in, procedures that fuse certain bones or remove a damaged bone can relieve pain.
• Rehabilitation: Hand therapy after treatment restores motion, strength, and function.

Because results are generally better when the injury is treated early, prompt evaluation of significant wrist injuries is important.

Prevention

This injury cannot always be prevented, but some measures lower the risk:

• Wear wrist guards for skating, skiing, and snowboarding
• Use proper technique and protective gear in sports
• Strengthen the wrist and forearm to support the joint
• Reduce fall hazards and improve balance
• Seek prompt evaluation of wrist pain after a fall rather than assuming it is a minor sprain

When to See a Doctor

See a doctor for wrist pain, swelling, clicking, or a sense of instability that persists after a fall or injury, even if early X-rays were read as normal. Because this ligament injury can be missed and is easier to treat early, persistent symptoms deserve a careful evaluation, ideally by a hand or wrist specialist.

Seek prompt or emergency care if the wrist is visibly deformed, severely swollen, or if the hand becomes numb, tingly, pale, or cold, which can indicate a more serious injury involving nerves, blood vessels, or a dislocation.

Related Topics

Frequently Asked Questions

References

1. American Society for Surgery of the Hand. Scapholunate ligament injury.
2. American Academy of Orthopaedic Surgeons (OrthoInfo). Wrist Sprains.
3. Mayo Clinic. Sprained wrist — Symptoms and causes.
4. MedlinePlus, U.S. National Library of Medicine. Wrist injuries and disorders.