The scapholunate (SL) ligament connects the scaphoid and lunate bones and is a critical stabilizer of the wrist, allowing these two bones to move in coordinated fashion during wrist motion. A scapholunate ligament tear disrupts this coordination, potentially leading to progressive wrist instability, abnormal load distribution across the carpus, and eventual arthritis.
Scapholunate ligament tears are one of the most clinically important — and most frequently missed — wrist injuries. Many are initially dismissed as sprains, only to present months or years later with chronic pain or established arthritis. If left untreated, scapholunate instability progresses in a predictable pattern to SLAC wrist (scapholunate advanced collapse). Early diagnosis with MRI is essential to intervene before this progression occurs. Scapholunate tears are also frequently associated with distal radius fractures and can coexist with TFCC tears.
Causes
- Fall on an outstretched hand (FOOSH): The most common mechanism — force transmitted through an extended, dorsiflexed, and ulnarly deviated wrist can tear the scapholunate ligament.
- Sports-related injuries: Snowboarding, skating, gymnastics, football, and cycling — any sport involving falls or significant wrist loading — are frequent causes.
- High-energy trauma: Motor vehicle accidents, falls from height, and industrial injuries can cause scapholunate tears, often alongside fractures and other ligament injuries.
- Associated with distal radius fractures: Scapholunate ligament tears accompany distal radius fractures in up to 30% of cases — a key reason MRI is valuable after wrist fracture.
- Repetitive wrist stress: Chronic repetitive loading with forceful wrist extension — weightlifting, racquet sports, impact tool use — can cause progressive ligament attrition and tearing.
- Degenerative causes: Age-related ligament wear or calcium pyrophosphate deposition disease can lead to tears without significant trauma in older adults.
- Inflammatory conditions: Rheumatoid arthritis and other inflammatory arthritides can weaken the scapholunate ligament and predispose to rupture.
Symptoms
- Dorsal radial wrist pain: Pain on the back and thumb side of the wrist — the hallmark symptom — worse with wrist extension, gripping, and weight-bearing.
- Swelling: Localized swelling over the dorsal wrist at the scapholunate interval.
- Tenderness: Point tenderness just distal to Lister's tubercle on the back of the wrist.
- Clicking or clunking: A clicking, clunking, or popping sensation with wrist motion — particularly with forceful gripping or wrist extension — is a characteristic finding.
- Weakness: Reduced grip strength compared to the uninjured side.
- Decreased range of motion: Particularly wrist extension, due to pain and mechanical dysfunction.
- Instability: A sense of wrist giving way or feeling unstable with loading.
- Delayed or missed diagnosis: Many scapholunate injuries are initially dismissed as sprains and diagnosed only after chronic pain or arthritis has developed — underscoring the importance of early MRI evaluation.
Diagnosis
Physical examination includes palpation for tenderness over the scapholunate interval and the Watson test (scaphoid shift test) — pressure applied to the scaphoid while moving the wrist detects abnormal scaphoid motion, indicating instability. X-rays (including a clenched fist AP view) are the first imaging study. Key X-ray findings include a widened scapholunate gap greater than 3 mm ("Terry Thomas sign"), the "signet ring sign" of scaphoid flexion, an increased scapholunate angle on lateral view, and — in chronic cases — early arthritis at the radioscaphoid joint.
However, many scapholunate tears — particularly partial tears and early complete tears — are not visible on X-ray. A dedicated wrist MRI directly visualizes the scapholunate ligament, identifies the location and extent of tearing, detects associated bone marrow edema, and evaluates for concurrent TFCC injury and chondral damage. MRI arthrography — with contrast injected into the wrist joint — provides the highest sensitivity for subtle partial tears. Early MRI diagnosis is critical because the window for primary ligament repair closes within approximately 6 weeks of injury.
Classification (Geissler)
Scapholunate ligament injuries are classified using the Geissler arthroscopic grading system:
- Grade I: Ligament attenuation or hemorrhage seen from the radiocarpal joint; no incongruency at the scapholunate interval from the midcarpal joint.
- Grade II: Attenuation or hemorrhage from the radiocarpal joint; incongruency or step-off visible from the midcarpal joint.
- Grade III: Incongruency visible from both radiocarpal and midcarpal joints; a probe can be passed between the scaphoid and lunate.
- Grade IV: Gross instability from both joints; a 2.7 mm arthroscope can be passed through the interval ("drive-through sign").
Tears are also classified by duration:
- Acute (<6 weeks): Best candidates for primary ligament repair.
- Subacute (6 weeks – 6 months): Repair may still be possible but more technically challenging.
- Chronic (>6 months): Direct repair usually not possible; reconstruction required.
- Chronic with arthritis (SLAC wrist): Advanced stage requiring salvage procedures.
Treatments
Treatment depends on tear severity, chronicity, associated injuries, patient age, and functional demands.
Conservative treatment: For partial tears or low-grade injuries (Geissler I–II), splinting or casting, activity modification, NSAIDs, and hand therapy can be effective. Corticosteroid injection may provide temporary pain relief but does not address underlying instability.
Surgical treatment for acute tears (active patients)
Acute complete tears diagnosed within 6 weeks of injury are best treated with primary repair, which offers the greatest chance of restoring normal anatomy:
- Ligament repair: The torn ligament ends are reattached using suture anchors, and the scaphoid and lunate are temporarily stabilized with K-wires while healing occurs.
- Capsulodesis: Augmentation of the repair with a flap of dorsal wrist capsule to reinforce stability.
Surgical treatment for chronic tears
When direct repair is no longer possible, ligament reconstruction is required:
- Ligament reconstruction: The ligament is reconstructed using a tendon graft — often a portion of the flexor carpi radialis.
- Brunelli procedure and modifications: A tendon graft passed through a tunnel in the scaphoid reconstructs the ligament.
- RASL procedure: A screw holds the scaphoid and lunate in proper alignment while the ligament heals.
Salvage procedures for SLAC wrist
When arthritis has developed, reconstruction is no longer feasible and salvage options are considered:
- Proximal row carpectomy (PRC): Removal of the scaphoid, lunate, and triquetrum — the capitate articulates with the radius, preserving useful wrist motion.
- Four-corner fusion: Fusion of the lunate, capitate, hamate, and triquetrum with scaphoid excision — good pain relief while preserving some motion.
- Total wrist fusion: Complete wrist fusion for advanced multi-joint arthritis — eliminates pain but also eliminates wrist motion.
Rehabilitation
Post-operative immobilization in cast or splint for 6–12 weeks is followed by a structured hand therapy program to restore range of motion, strength, and function. Full recovery typically takes 6–12 months. Return to heavy labor or high-impact sports may be limited, and some patients have permanent activity restrictions depending on the procedure performed.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Wrist MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.