The right treatment for a scapholunate ligament injury depends entirely on the stage — a partial tear caught early is a completely different problem than chronic instability. Dr. Graham tailors the approach to what the injury actually is: immobilization for partial tears, direct repair for acute complete tears, tendon graft reconstruction for chronic instability, and salvage for established arthritis.
Scapholunate injuries are frequently misdiagnosed as wrist sprains. If your pain has persisted more than 4–6 weeks after a wrist injury, formal evaluation is warranted.
Understanding the Injury
The scapholunate (SL) ligament is a C-shaped structure connecting the scaphoid and lunate — two adjacent bones in the proximal row of the wrist. It is the primary stabilizer of the most mechanically important articulation in the wrist, and its integrity is what allows the proximal carpal row to function as a coordinated unit during wrist motion and load transfer.
When the SL ligament is torn — most commonly from a fall on an outstretched hand, a high-energy impact, or a twisting injury — the scaphoid and lunate lose their coupled motion. The scaphoid tends to flex and pronate while the lunate extends, creating a gap visible on X-ray and a progressive pattern of instability. This malalignment, if not addressed, drives cartilage wear in a predictable sequence known as SLAC (scapholunate advanced collapse) arthritis.
What makes SL ligament injuries particularly consequential is their tendency to be misdiagnosed as routine wrist sprains. The window for direct repair — when the torn ligament can simply be reattached — is narrow. Once the injury becomes chronic, the treatment options change entirely. Early and accurate diagnosis is everything.
The scapholunate ligament sits between the scaphoid and lunate bones. When torn, the scaphoid flexes while the lunate extends — creating the DISI (dorsal intercalated segment instability) deformity visible on lateral X-ray.
The gap between the scaphoid and lunate on a PA X-ray — the "Terry Thomas sign" — indicates static instability, meaning the secondary restraints have also failed. A normal-appearing X-ray at rest does not rule out dynamic instability.
Recognizing the Injury
SL ligament injuries are frequently written off as wrist sprains. These are the features that should prompt formal evaluation.
Pain localizes to the dorsoradial wrist — the back of the wrist on the thumb side, roughly between the scaphoid and lunate. It is often reproduced with loading the wrist in extension or with radial deviation.
A reproducible clunk or click during wrist motion — particularly during radial-to-ulnar deviation — can indicate the scaphoid subluxing. This is also what the Watson shift test attempts to reproduce in the clinic.
The wrist feels unstable under load. Grip strength decreases and patients notice difficulty with tasks that require a forceful grip or axial loading through the wrist — tools, lifting, pushing off.
Dorsal wrist swelling following a fall on an outstretched hand is the most common acute presentation. Even when initial X-rays appear normal, significant swelling over the dorsoradial wrist warrants further evaluation before dismissing the injury as a simple sprain.
A wrist sprain that hasn't substantially improved within 4–6 weeks should be re-evaluated. Scapholunate injuries are commonly misdiagnosed at the time of the acute injury — and the diagnosis is often delayed until symptoms persist beyond what a typical sprain would produce.
A gap greater than 3mm between the scaphoid and lunate on a PA wrist X-ray — the "Terry Thomas sign" — indicates static instability. Some patients are referred after this finding is noted incidentally on imaging obtained for another reason.
How the Diagnosis Is Made
Accurate staging requires combining clinical examination, imaging, and often direct arthroscopic assessment. Each modality contributes something the others cannot.
The Watson scaphoid shift test is the key provocative maneuver. With the wrist in ulnar deviation, the examiner places thumb pressure on the scaphoid tuberosity and passively moves the wrist into radial deviation. In a positive test, the scaphoid subluxes over the dorsal rim of the radius, producing a painful clunk that the patient recognizes as their symptom. A positive Watson test in the right clinical context is a strong indicator of SL ligament pathology.
Standard PA and lateral wrist X-rays are the first step — looking for SL gap widening, scaphoid ring sign, and DISI alignment on lateral view. Stress views under fluoroscopy can unmask dynamic instability that static films miss. MRI arthrogram — with gadolinium injected into the joint — improves sensitivity for ligament tears significantly over standard MRI and provides information about tissue quality and secondary restraints. Together, stress films and MRI arthrogram are the most helpful pre-operative studies.
Wrist arthroscopy provides direct visualization of the SL ligament, allows dynamic assessment of carpal stability under traction, and grades the tear using the Geissler classification. It is the most accurate way to confirm the diagnosis, assess tissue quality — which determines whether primary repair is feasible — and evaluate the cartilage for early SLAC changes that would change the treatment plan. For equivocal cases or when surgical planning requires definitive staging, arthroscopy is the answer.
Treatment Decision Framework
The stage of injury — not just the diagnosis — determines what is appropriate. These four clinical presentations require four different approaches.
Dorsal wrist pain with a partial SL ligament tear on MRI arthrogram or arthroscopy, but no gap on static X-ray and no clear instability on stress views. The secondary stabilizers — the dorsal intercarpal ligament and the radioscaphocapitate — are intact and compensating for the partial tear.
Many partial tears do not progress to instability, and surgery in the absence of clear instability adds risk without a defined benefit.
An acute complete SL ligament tear where the ligament tissue is still present and repairable, or dynamic instability where stress views or arthroscopy reveal abnormal carpal motion not yet visible on static films. Time is the critical variable — the repair window is open, and the secondary restraints are still intact enough to allow direct reconstruction.
Delay allows retraction and degeneration of the torn ligament edges, secondary restraint failure, and progression toward static instability. Acute repair, ideally within weeks, gives the best chance of restoring native SL mechanics.
The SL ligament has been torn for long enough that the native tissue can no longer be directly repaired — it has retracted, degenerated, or become scarred. However, the scapholunate relationship is still reducible: the joint can be brought back into anatomic alignment manually or under anesthesia, and no cartilage damage has yet developed on imaging.
This is the window for ligament reconstruction rather than salvage. Once the deformity becomes fixed or arthritis appears, reconstruction is no longer appropriate.
When the scapholunate gap has become fixed and irreducible, when DISI deformity is established on lateral X-ray, or when SLAC arthritis has developed with cartilage loss at the radial styloid and/or the radioscaphoid articulation, ligament repair or reconstruction is no longer the appropriate treatment. The joint surfaces are already damaged, and restoring the ligament alone will not address the pain or halt the arthritis.
Salvage procedures for end-stage SLAC wrist — including proximal row carpectomy (PRC), scaphoid excision with four-corner fusion (capitolunate fusion), and total wrist fusion — are covered on the dedicated SLAC Wrist page. The right procedure depends on the pattern of arthritis, the patient's age and activity demands, and what motion is worth preserving.
Surgical Techniques
Two distinct operations for two distinct stages of injury — the choice between them is made based on tissue quality and chronicity, confirmed at arthroscopy.
When the SL ligament tissue is still present and viable — confirmed at arthroscopy — Dr. Graham performs direct repair through a dorsal approach. Suture anchors are placed into the scaphoid and/or lunate, the ligament is pulled back down to bone under appropriate tension, and the repair is completed.
K-wire pinning across the scapholunate joint is always added as an adjunct. The pins protect the repair from the loading forces that would otherwise stress the healing tissue during the critical early weeks. Dr. Graham does not pin without repairing or reconstructing — the pin is not the treatment; it is the protection for the treatment.
When the native ligament is no longer repairable — too degenerated, too retracted, or too scarred — Dr. Graham reconstructs the dorsal SL ligament using a strip of the extensor carpi radialis brevis (ECRB) tendon. This tendon is accessible through the same dorsal approach, and harvesting a portion of it does not meaningfully compromise wrist extension strength.
The graft is routed through bone tunnels drilled in the scaphoid and lunate and secured to recreate the dorsal SL ligament, restoring the mechanical constraint that prevents the scaphoid from flexing away from the lunate. K-wire pinning again protects the reconstruction during healing.
"Pauline Hartje — a complex wrist fracture. Dr. Graham called the next morning to check in, and the scar was essentially invisible."
Pauline Hartje · Wrist Surgery Patient · Verified Google Review ★ 5/5
Biologic Treatment Option
Complete scapholunate ligament tears with instability are surgical problems — the carpal bones are dissociating and biological repair alone cannot restore stability. But partial scapholunate tears, incomplete injuries without dynamic instability, and patients being managed conservatively while awaiting surgical timing represent genuine candidates for PRP as a biologic adjunct.
The scapholunate ligament has poor intrinsic vascularity — particularly its dorsal component, which is the primary stabilizer and the portion most commonly torn. This limited blood supply is precisely why ligament healing is slow and why partial tears can fail to resolve with rest alone. PRP's concentrated growth factors, delivered directly to the tear site under imaging guidance, may support a more complete healing response in a structure that lacks the biological resources to do so independently.
Dr. Graham considers PRP a reasonable adjunct for carefully selected scapholunate cases — particularly partial tears in patients who are not yet surgical candidates or who want to maximize conservative management. It is not a substitute for surgery in patients with frank instability, but for the right presentation it is a sensible biologic step. Ask Dr. Graham whether your specific tear pattern makes PRP a logical part of your treatment plan. Full procedure details are on the PRP treatment page.
Common Questions