What is the appropriate diagnosis and management for a 40-year-old female with acute onset of severe pain at the knee and collar (sternoclavicular) joints for the last 2 days?

Acute Polyarticular Joint Pain: Diagnosis and Management

This 40-year-old woman presenting with acute severe pain in multiple joints (knee and sternoclavicular) over 2 days requires immediate evaluation for inflammatory arthritis, particularly septic arthritis or crystal-induced arthropathy, rather than traumatic injury. The bilateral/polyarticular nature and lack of trauma history distinguish this from typical knee trauma cases.

Critical Initial Assessment

The most urgent priority is ruling out septic arthritis, which is an orthopedic emergency requiring immediate intervention. 1

Red Flags Requiring Urgent Evaluation:

• Fever and systemic symptoms strongly suggest septic arthritis 1
• Inability to bear weight or move the joint 1
• Severe joint swelling with erythema 2
• Recent bacteremia or infection elsewhere 1

Key Clinical Features to Assess:

• Presence of joint effusion in the knee (indicates significant pathology) 3, 2
• Focal bony tenderness versus diffuse joint tenderness 1
• Range of motion limitation (inability to flex knee to 90° is concerning) 4
• Systemic symptoms: fever, chills, malaise 1, 2
• Pattern of joint involvement: polyarticular involvement suggests inflammatory/systemic process rather than trauma 5

Diagnostic Approach

Initial Imaging:

Plain radiographs (AP and lateral views) of the affected knee should be obtained as the initial imaging study. 4, 3, 6 This is appropriate even without trauma history when evaluating acute severe joint pain to assess for:

• Fractures or bony abnormalities
• Joint effusion
• Degenerative changes
• Osteochondral defects 6

However, this patient does NOT meet Ottawa knee rule criteria (age <55, no trauma mechanism described), so radiographs are clinically indicated based on severity of symptoms and need to rule out other pathology, not trauma protocols. 4

Laboratory Evaluation:

Given the polyarticular presentation without trauma:

• Urgent joint aspiration with synovial fluid analysis if significant effusion is present and infection is suspected 1
• Inflammatory markers: ESR, CRP (CRP >2.0 mg/dL increases probability of septic arthritis) 1
• Complete blood count with differential 2
• Serum uric acid (for gout evaluation) 7
• Blood cultures if fever present 1

Synovial Fluid Analysis Should Include:

• Cell count with differential
• Gram stain and culture
• Crystal analysis (for gout/pseudogout)

Note: Plain films are neither sensitive nor specific for pseudogout diagnosis 7, so synovial fluid crystal analysis is essential if crystal arthropathy is suspected.

Differential Diagnosis Priority

Most Likely Diagnoses in This Context:

1. Acute gout or pseudogout (crystal-induced arthropathy)

   • Can affect knee and sternoclavicular joints
   • Acute onset over 1-2 days is typical 8
   • Severe pain characteristic 8

2. Septic arthritis (MUST be ruled out urgently)

   • Can be polyarticular in 10-20% of cases
   • Requires immediate intervention 1

3. Reactive arthritis or other inflammatory arthropathy

   • Polyarticular involvement
   • Acute onset possible 5

Less Likely Given Presentation:

• Traumatic injury: No trauma history, bilateral joint involvement atypical 4, 2
• Osteoarthritis flare: Would expect age >50 years and chronic symptoms 9, 7
• Meniscal tear: Requires trauma mechanism, unilateral 9

Management Algorithm

If Septic Arthritis Suspected or Cannot Be Ruled Out:

1. Immediate orthopedic consultation
2. Urgent joint aspiration (ultrasound-guided if needed) 1
3. Empiric IV antibiotics after cultures obtained
4. Hospital admission

If Crystal Arthropathy Most Likely (After Excluding Infection):

For acute gout, naproxen 750 mg initially, followed by 250 mg every 8 hours until attack subsides 8

• Favorable response typically seen within 24-48 hours with clearing of inflammatory changes 8
• Alternative: other NSAIDs, colchicine, or corticosteroids depending on contraindications

Conservative Management (If Non-Urgent Inflammatory Process):

• NSAIDs: Naproxen 500 mg twice daily or 250 mg every 6-8 hours 8
• Rest and ice to affected joints
• Close follow-up within 24-48 hours to reassess response

Critical Pitfalls to Avoid

• Do NOT assume traumatic etiology without clear trauma history - polyarticular involvement suggests systemic process 5
• Do NOT delay joint aspiration if infection is possible - septic arthritis is an emergency 1, 2
• Do NOT rely on plain films alone for pseudogout diagnosis - crystal analysis is required 7
• Do NOT apply Ottawa knee rules rigidly - these are designed for trauma patients, and physician judgment should supersede guidelines when clinical picture suggests alternative diagnosis 4
• Do NOT start empiric antibiotics before obtaining cultures unless patient is septic 1

Follow-up Considerations

If symptoms persist beyond 5-7 days despite treatment, or if mechanical symptoms or instability develop, MRI may be considered 3 to evaluate for:

• Soft tissue pathology
• Occult fractures
• Internal derangement

Specialist referral (rheumatology or orthopedics) is appropriate if diagnosis remains unclear after initial workup or if inflammatory arthropathy is confirmed requiring disease-specific management.