Carpal Boss
Wrist Bone Spur
Jacksonville, FL
A hard, bony bump on the back of the wrist at the base of the index or middle finger — not a cyst, not a tumor. R. David Graham, MD at JOI evaluates carpal boss carefully, because the key clinical distinction is whether the bump is a true bony prominence (carpal boss) or a ganglion cyst overlying the CMC2-3 joint — which changes the procedure entirely.
- Carpal boss = bony prominence at CMC2 or CMC3 joint on dorsal wrist
- Hard and non-compressible — distinguishes from ganglion cyst (soft, transilluminates)
- Often asymptomatic — found incidentally
- Symptomatic: cortisone injection first
- Surgical: osteoarthrectomy (excision of bony prominence) when refractory
- Always distinguish from overlying ganglion — changes the operative plan
The carpal boss sits at the CMC2-3 joint level on the dorsum of the wrist and is confirmed on a lateral X-ray. A ganglion cyst can overlie the same joint and look similar — but the treatment is different. Examining the bump under transillumination and obtaining a lateral X-ray clarifies the diagnosis at the first visit.
Understanding Carpal Boss
Bony Prominence at the
Base of the Wrist
A carpal boss is an osteophyte — a bony prominence — that develops at the carpometacarpal (CMC) joint at the base of the index or middle finger on the dorsum of the wrist. It is a form of localized degenerative arthritis at the CMC2 or CMC3 joint, where a bony spur forms on the dorsal surface of the joint. Carpal bosses are common, often discovered incidentally, and frequently asymptomatic.
When symptomatic, the carpal boss produces dorsal wrist pain at the prominence with wrist extension and gripping activities, and tenderness to direct palpation over the bony bump. The clinical examination is usually straightforward: the bump is hard and non-compressible, does not transilluminate (distinguishing it from a ganglion cyst), and is confirmed on lateral wrist X-ray as a bony prominence at the CMC joint level.
The critical distinction Dr. Graham makes at every carpal boss evaluation: is this a pure bony boss, or is there a ganglion cyst overlying the CMC2-3 joint? A ganglion can arise from the CMC joint capsule and sit in the same location as a carpal boss — sometimes both are present simultaneously. If a ganglion is present, the operative plan changes: the ganglion must be excised in addition to the bony prominence, and the joint capsule stalk must be identified and resected. Missing a concurrent ganglion is the most common reason for recurrence after carpal boss excision.
- ✓ Carpal boss: hard, non-compressible, does not transilluminate, visible on X-ray
- ✓ Ganglion cyst: soft, compressible, transilluminates with light, not visible on X-ray
- ✓ Both can occur at the CMC2-3 joint dorsum simultaneously
- ✓ Lateral wrist X-ray confirms bony prominence for carpal boss
- ✓ MRI distinguishes when clinical exam is equivocal
- ✓ Operative plan differs — ganglion requires stalk excision from joint capsule
Treatment
Injection First — Osteoarthrectomy When Refractory
Confirm the Diagnosis
Lateral wrist X-ray confirms bony prominence at CMC2-3. Clinical exam distinguishes boss from ganglion — transillumination and compressibility. MRI when both are present or when exam is equivocal.
Cortisone Injection (Symptomatic Boss)
Injection into the CMC joint at the carpal boss reduces inflammation and frequently provides lasting relief for the arthritic component. Repeated as needed. Significant relief with injection confirms the carpal boss as the pain source.
Osteoarthrectomy — Refractory Cases
Surgical excision of the bony prominence through a small dorsal incision over the CMC joint. The osteophyte is excised with an osteotome to the level of normal joint architecture. Any concurrent ganglion cyst is excised at the same time, including its capsular stalk. The extensor tendons are mobilized and protected throughout. Short-arm splint 2 weeks, then progressive motion.
FAQs
Frequently Asked Questions
Related Conditions
Next Steps
Hard bump on the back of the wrist —
diagnosed and treated at the first visit.
Carpal boss evaluation includes X-ray confirmation and clinical distinction from a ganglion cyst at the same visit. If symptomatic, injection can be performed at the first visit as well.
Jacksonville Beach, FL 32250
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