What is the diagnosis and treatment for a reddened bump on the thumb joint that is becoming larger and inflamed at times?

Diagnosis and Management of Reddened, Enlarging Thumb Joint Bump

Most Likely Diagnosis

This presentation most likely represents thumb carpometacarpal (CMC) osteoarthritis, which characteristically presents as bony enlargement at the thumb base with intermittent inflammation. 1

Differential Diagnosis Priority

Primary Consideration: Thumb CMC Osteoarthritis

• Bony prominence with intermittent inflammation at the thumb base is the clinical hallmark of thumb CMC osteoarthritis, affecting approximately 33% of postmenopausal women and presenting with pain on usage and mild morning stiffness 1, 2
• Risk factors include female sex, age over 40, menopausal status, family history, and prior hand injury 1
• The location near the thumb base strongly suggests carpometacarpal osteoarthritis as the primary diagnosis, as this is a characteristic target site, and true bony prominence supports degenerative rather than inflammatory pathology 1

Alternative Diagnoses to Exclude

• Gout can superimpose on pre-existing hand osteoarthritis but typically presents with acute inflammatory episodes rather than chronic progressive bony prominence 1
• Herpetic whitlow should be considered if there are recurrent vesicular lesions or history of viral prodrome, though this typically lacks bony prominence 3
• Rheumatoid arthritis affects the thumb metacarpophalangeal joint more commonly than the CMC joint and presents with soft tissue swelling rather than bony enlargement 4

Diagnostic Workup Algorithm

Step 1: Initial Imaging

Plain radiographs are always indicated as the initial imaging study for suspected wrist/thumb pathology 1

• Order 3-view radiographs of the thumb to look for joint space narrowing, osteophytes, subchondral sclerosis, and subchondral cysts characteristic of osteoarthritis 1
• These findings confirm the diagnosis of thumb base osteoarthritis 1

Step 2: Advanced Imaging (If Radiographs Equivocal)

• CT without IV contrast can exclude or confirm suspected pathology when radiographs are equivocal 1
• MRI without IV contrast can detect occult fractures and soft tissue pathology if diagnosis remains unclear 1

Step 3: Laboratory Testing (Selective)

• Blood tests are not required for diagnosis of hand osteoarthritis 1
• Consider laboratory studies only if marked inflammatory symptoms suggest coexistent inflammatory disease (ESR, CRP, rheumatoid factor, anti-CCP antibodies) 1
• Joint aspiration is indicated only if infection is suspected or to exclude crystalline arthropathy during acute inflammatory flares 5

Treatment Algorithm

First-Line Conservative Management (Mandatory Initial Approach)

Conservative treatment must be implemented first and continued for at least 6 months before considering surgery 6, 7

• Activity modification and patient education about joint protection techniques 6
• Thumb splinting/immobilization to reduce mechanical stress on the joint 6, 2
• Topical NSAIDs applied directly to the affected joint 6
• Oral analgesics (acetaminophen or NSAIDs) for pain control 6
• Exercise regimens focusing on range of motion and strengthening 6
• Heat application for symptomatic relief 6

Second-Line Treatment for Painful Flares

Intra-articular corticosteroid injection is the first-line invasive therapy for patients with persistent pain despite conservative measures 6, 2

• Steroid injections combined with immobilization relieve symptoms in approximately 72% of patients 2
• This provides temporary relief but does not alter disease progression 2

Third-Line Surgical Intervention

Surgery should be considered only when marked pain and/or disability persist after at least 6 months of conservative treatment failure 6, 7

Surgical Options:

• Trapeziectomy (with or without ligament reconstruction) and total joint arthroplasty are the two main surgical techniques in 2023 7
• Joint-sparing procedures (ligament reconstruction, osteotomy, denervation) may be considered in specific cases 7
• Trapeziometacarpal fusion is reserved for very specific indications 7

Critical Pitfalls to Avoid

• Do not proceed to surgery without exhausting conservative measures first - the treatment algorithm requires stepwise progression through all non-surgical options 6
• Do not delay radiographic evaluation - plain films should be obtained promptly to confirm diagnosis and exclude other pathology 1
• Do not perform joint aspiration routinely - this is indicated only when infection or crystalline arthropathy is suspected, not for routine osteoarthritis diagnosis 5, 1
• Do not assume all thumb base swelling is osteoarthritis - consider infectious causes (herpetic whitlow) if there are recurrent episodes with vesicular features 3