What is the cause and treatment of thumb swelling with reduced range of motion (ROM) in the absence of any injury?

Thumb Swelling with Reduced ROM Without Injury

For atraumatic thumb swelling with reduced range of motion, the most likely diagnosis is thumb carpometacarpal (CMC) osteoarthritis, and you should begin with standard three-view radiographs (posteroanterior, lateral, and oblique) of the hand and wrist to establish the diagnosis, followed by first-line treatment with a full splint covering both the thumb base AND wrist combined with topical NSAIDs. 1

Initial Diagnostic Approach

• Obtain standard three-view radiographs (posteroanterior, lateral, and oblique) of the hand and wrist as the most appropriate initial imaging study, which will likely establish the diagnosis of thumb CMC osteoarthritis in this clinical presentation 1
• Standard radiographs are essential and sufficient for diagnosis in most cases, showing joint space narrowing, osteophytes, and subluxation patterns 1
• Do not order MRI or advanced imaging initially unless radiographs are normal or show only nonspecific findings, as this adds cost without diagnostic benefit 1

Differential Diagnosis Considerations

While thumb CMC osteoarthritis is most common with this presentation, also consider:

• Trigger finger if the swelling is more localized to the flexor tendon sheath and there is catching or locking with finger motion 2
• De Quervain's tenosynovitis if pain and swelling are on the radial (thumb) side of the wrist
• Inflammatory arthropathy if there are systemic symptoms or involvement of other joints

First-Line Conservative Treatment

Splinting

• Use a full splint that covers both the thumb base AND wrist, as this provides superior pain relief compared to thumb-only splints (NNT = 4 for improving daily activities) 1
• Avoid using thumb-only splints when a full splint including the wrist provides better pain control 1

Topical NSAIDs

• Topical NSAIDs are the preferred pharmacological treatment for mild to moderate pain, as they provide equivalent pain relief to oral NSAIDs (effect size 0.77) without increased gastrointestinal complications 1
• Do not proceed directly to oral NSAIDs without first trying topical NSAIDs, which have equivalent efficacy with better safety profiles 1

Activity Modification

• Recommend activity modification and education about avoiding adverse mechanical factors as first-line treatment 2
• Heat application, such as paraffin wax or hot packs, may provide symptomatic relief, especially when applied before exercise 2

Exercise

• Instruct the patient to perform active finger motion exercises to prevent finger stiffness, which is one of the most functionally disabling adverse effects 3
• Exercise regimens involving both range of motion and strengthening exercises are recommended to maintain thumb and finger mobility 2

Second-Line Pharmacological Options

If topical NSAIDs and splinting are insufficient:

• Oral paracetamol (up to 4g/day) has the best safety profile and should be tried next 1, 2
• Oral NSAIDs at the lowest effective dose for the shortest duration if paracetamol fails, with addition of gastroprotection (PPI or H2-blocker) in patients with GI risk factors 1, 2
• Avoid COX-2 inhibitors in patients with cardiovascular risk factors 1, 2

Interventional Treatment

If conservative measures fail:

• Intra-articular corticosteroid injection may provide short-term benefit for painful flares, though evidence is limited and effects may not persist beyond one month 1, 2
• Intra-articular hyaluronan is an alternative with potentially more prolonged benefit than corticosteroid 1

Surgical Intervention

• Surgery should be considered when conservative treatments fail AND the patient has marked pain and/or disability affecting quality of life 1, 4
• Trapeziectomy alone is the recommended surgical approach, as combination procedures (trapeziectomy with ligament reconstruction and tendon interposition) provide no additional benefit but cause significantly more complications (RR 2.12,95% CI 1.24-3.60) 1
• Do not perform complex surgical procedures when simple trapeziectomy provides equivalent outcomes with fewer complications 1

Common Pitfalls to Avoid

• Do not apply ice directly to the skin for acute swelling, as this can cause cold injury; use ice and water surrounded by a damp cloth and limit application to 20-30 minutes 3
• Remove rings and other constricting jewelry from the swollen thumb to avoid constriction and damage to the finger 3
• Reevaluate patients with unremitting pain during follow-up, as this may indicate complications or alternative diagnoses 3
• Do not operate without exhausting conservative measures first, as the treatment algorithm requires stepwise progression through non-pharmacological, pharmacological, and invasive non-surgical options 4