How should I evaluate and initially treat an adult presenting with metacarpophalangeal joint pain, swelling, or limited motion?

Evaluation and Initial Treatment of MCP Joint Pain, Swelling, or Limited Motion

Begin with plain radiographs (PA, lateral, and oblique views) of the hand to identify fractures, dislocations, or bony pathology, followed by ultrasound as the first-line soft tissue imaging modality to evaluate for synovitis, effusion, tendon pathology, or ganglion cysts. 1

Initial Clinical Assessment

Key examination findings to document:

• Joint effusion or synovial proliferation on dorsal or palmar MCP joint palpation 1
• Range of motion limitations - normal MCP flexion is 0-90 degrees with constant lateral deviation from 0-70 degrees, then marked decrease beyond 70 degrees 2
• Functional impact on activities of daily living to determine treatment urgency 3
• Pattern of joint involvement - assess all MCP joints bilaterally, as polyarticular involvement suggests inflammatory arthritis 1
• Associated findings including morning stiffness duration, warmth, erythema, or palpable masses 1, 3

Imaging Algorithm

Standard radiographic evaluation:

• Three-view hand series (PA, lateral, oblique) is the initial imaging study for all patients with MCP joint symptoms 1
• Look for fractures, joint space narrowing, erosions, osteophytes, or malalignment 1

Ultrasound indications (perform if radiographs negative or equivocal):

• Dorsal longitudinal and transverse scans are the standard protocol for MCP joint evaluation 1
• Ultrasound reliably detects: joint effusion, synovial proliferation, synovial cysts, tendinitis/tenosynovitis, cartilage thinning, erosions, ganglion cysts, rheumatoid nodules, and crystal deposition 1, 3
• Dynamic examination with active finger flexion/extension evaluates extensor tendon function 1, 3

MRI indications (if ultrasound inadequate or surgical planning needed):

• Collateral ligament injuries - MRI has 67% sensitivity and 91% specificity for MCP collateral ligament tears 1
• Tendon injuries requiring surgical planning - MRI ideal for evaluating flexor and extensor tendon pathology 1
• Volar plate injuries not involving bone - important to diagnose as untreated lesions cause contractures or joint laxity 1

Differential Diagnosis by Presentation Pattern

Monoarticular involvement:

• Ganglion cyst - most common soft tissue mass, firm, non-tender, fluctuates in size 3
• Trauma-related - collateral ligament tear, volar plate injury, occult fracture 1
• Septic arthritis - requires urgent arthrocentesis if suspected 1

Polyarticular involvement:

• Rheumatoid arthritis - MCP joints involved in 27-29% of patients with inflammatory arthritis 1
• Adult-onset Still's disease - MCP involvement in 29% of cases 1
• Osteoarthritis - less common in MCP joints compared to DIP/PIP joints 1
• Crystal arthropathy - gout or pseudogout 3

Red Flags Requiring Urgent Action

Suspect malignancy if:

• Rapid growth or mass >5 cm 3
• Deep location relative to fascia or fixed to underlying structures 3
• Pain or functional limitation disproportionate to size 3
• Action: Obtain core needle biopsy under image guidance before any attempted excision 3

Suspect infection if:

• Acute onset with warmth, erythema, and systemic symptoms 1
• Action: Perform arthrocentesis with synovial fluid analysis before antibiotics 1

Initial Treatment Algorithm

For inflammatory arthritis (RA, Still's disease):

• Refer to rheumatology for disease-modifying therapy 1, 4
• Joint protection education and assistive devices if functional limitation present 3, 4
• Splinting for joint instability or pain with use 3, 4

For ganglion cysts:

• Observation alone if asymptomatic or minimally symptomatic without functional impairment 3
• Aspiration for symptomatic cysts causing pain or functional impairment (note: 40-70% recurrence rate) 3
• Surgical removal if conservative management fails and symptoms persist or mass significantly impairs hand function 3

For traumatic injuries:

• Collateral ligament tears - acute tears may benefit from early surgical repair; chronic tears often require reconstruction 5
• Splinting in position of function (MCP flexion 70-90 degrees) for 3-6 weeks for stable injuries 4
• Early mobilization for stable injuries to prevent stiffness 5

For suspected fractures with negative initial radiographs:

• CT without contrast is the next imaging study to confirm or exclude occult fractures 1, 6

Common Pitfalls to Avoid

• Do not perform excisional biopsy without imaging if any concern for malignancy exists, as this compromises definitive surgical margins 3
• Do not assume all dorsal masses are benign ganglions - always obtain imaging to exclude other pathology 3
• Do not rely on single PA radiograph - multiple projections necessary for complete evaluation 1, 6
• Do not delay rheumatology referral for polyarticular inflammatory arthritis, as early intervention prevents joint destruction 1, 4
• Ensure proper ultrasound positioning to avoid missing associated tendon or ligamentous pathology 1, 3