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Arthritis

Thumb Arthritis (CMC / Basilar Joint Arthritis)

The most common site of arthritis in the hand. Complete guide to understanding, staging, and treatment options for thumb base arthritis.

Understanding Thumb Arthritis

Thumb carpometacarpal (CMC) arthritis, also called basilar joint arthritis, affects the joint at the base of the thumb where the first metacarpal meets the trapezium bone of the wrist. This "saddle joint" allows the thumb's unique range of motion but is prone to wear.

Epidemiology: CMC arthritis is extremely common, especially in postmenopausal women. Radiographic evidence is found in 25% of women and 8% of men over 55 years. Women are affected 10-15 times more often, likely due to hormonal factors and joint laxity.

Biomechanics: The thumb CMC joint experiences enormous forces during pinch - up to 12kg of compressive force per 1kg of pinch load. This explains why a seemingly small joint can cause such significant symptoms with everyday activities.

Eaton-Littler Classification

Stage I

Early

Normal joint space. Joint widening from synovitis. Articular cartilage intact.

Stage II

Moderate

Joint space narrowing. Osteophytes <2mm. Scaphotrapezial joint normal.

Stage III

Severe

Significant narrowing. Osteophytes >2mm. Subluxation. Scaphotrapezial joint normal.

Stage IV

Pantrapezial

Stage III plus scaphotrapezial (STT) joint arthritis.

Clinical Note: Symptoms often correlate poorly with X-ray findings. Some patients with advanced radiographic changes have minimal pain, while others with early changes are significantly symptomatic. Treatment is based on symptoms, not X-ray stage alone.

Signs & Symptoms

Clinical Presentation

• Pain at thumb base: Deep, aching pain localized to the thenar eminence

• Pain with pinch/grip: Especially opening jars, turning keys, writing

• Weakness: Reduced pinch strength, difficulty with fine motor tasks

• Stiffness: Morning stiffness, worse in cold weather

• Deformity: "Shoulder sign" - prominent thumb metacarpal base, "zig-zag" deformity

• Instability: Thumb feels weak or gives way

Functional Impact: Activities commonly affected include opening jars, turning doorknobs, writing, using scissors, pinching buttons, and any task requiring sustained pinch or grip force.

Diagnosis

Clinical Examination:

  • Grind test (CMC grind): Axial compression with rotation produces pain and crepitus. Most sensitive clinical test.
  • Shoulder sign: Prominent dorsoradial subluxation of the metacarpal base
  • Metacarpal adduction: First web space narrowing
  • MCP hyperextension: Compensatory "zig-zag" deformity
  • Pinch strength testing: Compare to opposite hand

X-rays: PA, lateral, and stress views (Robert view - hyperpronated PA). Assess joint space, osteophytes, subluxation, and STT joint involvement.

Differential Diagnosis: De Quervain's tenosynovitis, scaphotrapezial arthritis, FCR tendinitis, carpal tunnel syndrome, trigger thumb.

Treatment Options

Conservative Treatment (First Line)

Splinting:

  • Thumb spica or CMC splint - immobilizes the CMC joint
  • Wear at night and during aggravating activities
  • Custom-molded splints often more comfortable than prefabricated
  • 70% of patients report improvement with splinting

Medications:

  • NSAIDs - topical or oral
  • Acetaminophen for pain

Injections:

  • Corticosteroid injection - provides temporary relief (weeks to months)
  • Can be repeated 2-3 times per year if effective
  • Good diagnostic test if diagnosis uncertain

Hand Therapy:

  • Strengthening exercises
  • Joint protection techniques
  • Activity modification
Surgical Treatment

Indications:

  • Failed conservative treatment (typically 3-6 months)
  • Significant functional limitation
  • Persistent pain affecting quality of life

Surgical Options:

Trapeziectomy with LRTI: Most common. Remove trapezium, reconstruct ligaments with tendon (FCR or APL). Excellent long-term results.

Trapeziectomy alone: Simple excision. Similar outcomes to LRTI in some studies. Shorter surgery.

CMC Arthrodesis (Fusion): For young, high-demand patients. Eliminates pain but sacrifices motion. Strong pinch.

CMC Arthroplasty: Joint replacement. Preserves motion. Selected patients. Newer implants showing promise.

Suture Suspension: Newer technique using suture anchor to suspend metacarpal after trapeziectomy.

Recovery After Surgery

0-6 weeks
Immobilization
Thumb spica cast or splint. Finger exercises. Wound healing and soft tissue settling.
6-12 weeks
Mobilization
Removable splint. Hand therapy begins. Progressive thumb motion and light pinch.
3-12 months
Strengthening
Progressive strengthening. Pinch strength continues to improve. Return to full activities.

Outcomes: Pain relief is typically excellent (90%+). Pinch strength may take 6-12 months to return and often exceeds pre-operative levels. Some motion loss is expected but usually well-tolerated.

Evidence & References

  • • Eaton RG, Littler JW. Ligament reconstruction for the painful thumb carpometacarpal joint. JBJS. 1973
  • • Wajon A, et al. Surgery for thumb (trapeziometacarpal) joint osteoarthritis. Cochrane Database Syst Rev. 2015
  • • Vermeulen GM, et al. Treatment of thumb carpometacarpal osteoarthritis: a systematic review. Clin Orthop Relat Res. 2011
  • • Day CS, et al. Comparison of surgical techniques for treating thumb carpometacarpal arthritis. Hand. 2008

Last Updated: January 2025 | Content reviewed by Dr. Deepthi Nandan Reddy, FRCS (Ortho)

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