Scapholunate Ligament Injury

The scapholunate ligament is a small but critical band of tissue inside your wrist that holds two of the eight wrist bones — the scaphoid and the lunate — in proper alignment. It's the single most important stabilizer in the wrist. When it tears (partly or all the way), those two bones drift apart and start moving in ways they shouldn't. Left alone, that wear pattern leads to a specific kind of wrist arthritis called SLAC wrist (scapholunate advanced collapse), where the cartilage progressively wears out over years.

It almost always tears from a fall onto an outstretched hand. The classic symptoms are pain on the back of the wrist about an inch out from your forearm, a weaker grip, and pain when you push down through the wrist (like pushing yourself up out of a chair).

• Pain on the back of the wrist, roughly an inch toward the thumb from center, especially with gripping or pushing
• Swelling on the back of the wrist after a fall onto an outstretched hand
• A weaker grip than you're used to — trouble opening jars or carrying heavy bags
• A clicking or clunking feeling inside the wrist with certain motions
• Pain when pushing down through the wrist — like doing a push-up or pushing yourself out of a chair
• Stiffness and loss of wrist range of motion, especially bending the wrist back (extension)

On exam, your provider does the Watson test — pressing on the scaphoid bone while moving the wrist side to side — and feels for an abnormal click or pain. X-rays sometimes show a wider-than-normal gap between the scaphoid and lunate (the so-called Terry-Thomas sign, named for the gap between the actor's front teeth) or the scaphoid appearing tilted and shortened (the ring sign). An MRI with contrast injected into the joint (MRI arthrography) is the most reliable non-invasive test, but the gold standard is wrist arthroscopy — a small camera inserted into the joint — which has the bonus of letting us treat the tear in the same session.

Complete tears where the bones have started to drift out of alignment need surgical repair (stitching the original ligament back together) or reconstruction (rebuilding the ligament with a tendon graft from elsewhere). Time matters — the longer you wait after the injury, the harder it gets to repair the original ligament, and the more often we have to reconstruct from scratch.

External patient-education references and related OSI pages for additional background:

• Britannica — Ligament
• Britannica — Hand (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language