What could be causing my thumb pain when I bend it, and how can I treat it?

Thumb Pain with Bending: Diagnosis and Treatment Algorithm

Your thumb pain with bending is most likely carpometacarpal (CMC) joint osteoarthritis, and you should start with a custom-made thumb orthosis worn during daily activities for at least 3 months combined with topical NSAIDs, followed by hand exercises targeting thumb base stability. 1, 2

Initial Diagnostic Considerations

The most common cause of thumb pain with bending in adults is thumb base (carpometacarpal) osteoarthritis, which affects approximately 33% of postmenopausal women radiographically and 20% require treatment for pain and disability. 3 Other possibilities include:

• De Quervain tenosynovitis - characterized by swelling of extensor tendons at the wrist, more common in women aged 40-59 years, particularly with frequent mobile phone use 3
• Trigger thumb - involves abnormal resistance to smooth flexion and extension 3
• Metacarpophalangeal (MCP) joint arthritis - less common but possible 4

Key physical examination findings for CMC arthritis include: localized tenderness at the thumb base, pain with grinding maneuvers, and visible subluxation or deformity at the CMC joint. 5, 6 Radiographic evaluation with at least 2 views should be obtained if structural abnormality is suspected. 2

First-Line Conservative Treatment (Start Here)

Orthotic Management

Prescribe a custom-made thermoplastic long thumb orthosis to be worn during activities of daily living for at least 3 months. 1, 2 This is critical because:

• Short-term use (less than 3 months) shows no benefit 1, 2
• Long-term use (≥3 months) demonstrates beneficial effects on pain and function 1
• A full splint covering both thumb base and wrist provides more pain relief than a half splint, with a number needed to treat of 4 for improving daily activities 2
• Custom-made orthoses by a specialized health professional improve compliance and long-term use 1

Topical Pharmacotherapy

Apply topical diclofenac gel as first-line pharmacological treatment. 1, 2 The evidence shows:

• Small improvements in pain and function after 8 weeks compared to placebo 1, 2
• Similar pain relief to oral NSAIDs but with significantly fewer gastrointestinal side effects 2
• Favorable safety profile even in elderly patients with comorbidities (age ≥65 years, hypertension, diabetes, cardiovascular disease) 1

Exercise Program

Initiate hand exercises aimed at improving joint mobility, muscle strength, and thumb base stability. 1, 2 Important points:

• Exercise regimens for the first carpometacarpal joint differ from those for interphalangeal joints 1, 2
• Multiple trials demonstrate small beneficial effects on pain, function, joint stiffness, and grip strength 1
• Benefits are not sustained when patients stop exercising, so ongoing adherence is essential 1, 2

Patient Education

Provide education on ergonomic principles, activity pacing, and use of assistive devices. 1, 2 This foundational care improves self-management and has demonstrated efficacy. 2

Second-Line Treatment (If Conservative Fails After 3 Months)

Oral Analgesics

If topical NSAIDs are insufficient, consider oral NSAIDs at the lowest effective dose for the shortest duration. 1, 7 However, you must assess cardiovascular, gastrointestinal, and renal risk factors first, particularly in elderly patients. 2

Intra-articular Corticosteroid Injection

Consider corticosteroid injection for painful flares, especially in the trapeziometacarpal joint. 2, 5 This is effective for temporary symptom relief, though evidence is primarily based on expert opinion. 2 Failure of corticosteroid injections indicates progression to surgical consultation. 8, 2

Third-Line Treatment (Surgical Intervention)

Surgery should be considered only when you have marked pain and/or disability limiting activities of daily living AND conservative treatments have failed. 1, 8, 2 The surgical options include:

• Trapeziectomy (with or without ligament reconstruction and tendon interposition) for thumb base OA 1, 9
• Arthrodesis for metacarpophalangeal or interphalangeal joint involvement 1, 4
• Arthroplasty as an alternative 1, 9

Multiple observational studies support surgery as clinically effective for severe thumb base OA refractory to conservative treatments. 8, 3

Critical Pitfalls to Avoid

• Do not expect immediate benefit from orthoses - no improvements are evident with use less than 3 months 1, 2
• Do not prescribe oral NSAIDs without assessing cardiovascular, gastrointestinal, and renal risk factors 2
• Do not proceed to surgery without exhausting conservative measures first - the treatment algorithm requires stepwise progression through non-pharmacological, pharmacological, and invasive non-surgical options 8, 2, 7
• Do not continue conservative management indefinitely without reassessment - escalate to injections or surgical consultation if symptoms remain severe after 3 months of appropriate conservative treatment 2

Treatment Timeline

1. Months 0-3: Custom thumb orthosis + topical diclofenac + exercises + education 1, 2
2. Month 3: Reassess - if inadequate relief, add oral NSAIDs or corticosteroid injection 1, 2
3. Month 6: If still severe pain/disability, refer for surgical evaluation 8, 2