What is the appropriate evaluation and treatment for a patient with a 1-day history of bilateral knee pain, finger joint pain, and plantar pain?

Acute Polyarticular Pain: Evaluation and Management

Immediate Priority: Rule Out Septic Arthritis and Systemic Inflammatory Disease

For a patient presenting with 1-day history of bilateral knee pain, finger joint pain, and plantar pain, the most critical first step is to assess for signs of infection (fever, erythema, warmth, effusion) and perform arthrocentesis if joint effusion is present, as delay in diagnosing septic arthritis can result in sepsis, bacteremia, joint destruction, or death. 1

Clinical Assessment Framework

Essential History Elements to Obtain

• Presence of fever, chills, or constitutional symptoms - these indicate possible septic arthritis or systemic inflammatory disease requiring urgent evaluation 1, 2
• Morning stiffness duration - stiffness lasting more than 30 minutes suggests inflammatory arthritis rather than mechanical causes 2, 3
• Skin manifestations - look specifically for psoriatic plaques on knees, elbows, genitals, scalp, or nail changes (pitting, onycholysis), as 25-30% of psoriasis patients develop psoriatic arthritis 4
• Recent trauma or twisting injury - helps distinguish traumatic from inflammatory causes 5, 3
• Ability to bear weight - inability to bear weight requires urgent evaluation 5
• Acute onset versus gradual - viral infections, crystal-induced arthritis, and serum sickness cause acute self-limited polyarthritis 2

Critical Physical Examination Findings

• Joint palpation for warmth, erythema, and effusion - presence of these with fever mandates immediate arthrocentesis before antibiotics 1
• Palpable synovitis - distinguishes inflammatory arthritis from osteoarthritis (which shows bony hypertrophy and crepitus) 2
• Dactylitis ("sausage digits") - highly suggestive of psoriatic arthritis 4
• Heel/Achilles tendon tenderness - indicates enthesitis, characteristic of psoriatic arthritis 4
• Distribution pattern - bilateral symmetric involvement suggests rheumatoid arthritis or viral arthritis; asymmetric suggests psoriatic arthritis or reactive arthritis 2

Diagnostic Algorithm

If Joint Effusion Present Without Recent Trauma

Perform arthrocentesis immediately - this is the single most important diagnostic test and should not be delayed 1

• Send synovial fluid for:

  • Cell count with differential 1
  • Gram stain and culture 1
  • Crystal analysis (monosodium urate for gout, calcium pyrophosphate for pseudogout) 1

• Inflammatory fluid (WBC >2000) with monosodium urate crystals indicates gout 1

• Inflammatory fluid with negative crystals and culture suggests inflammatory arthritis (rheumatoid, psoriatic, reactive) 1, 2

• Noninflammatory fluid (WBC <2000) suggests osteoarthritis 1

Initial Laboratory Testing

• Complete blood count - more useful than classic rheumatologic tests for initial evaluation 2
• Metabolic panel - provides diagnostic clues 2
• Urinalysis - helps identify systemic disease 2
• C-reactive protein - elevated in inflammatory conditions including psoriatic arthritis 4
• Rheumatoid factor - but recognize this is often negative in psoriatic arthritis 4

Important caveat: Many classic rheumatologic laboratory tests are nonspecific and should not guide initial management 2. Do not start treatment based solely on laboratory data such as elevated uric acid 1.

Imaging Strategy

• Plain radiographs of affected joints - obtain if focal bone pain, recent trauma, or to establish baseline 5, 2
• Radiographs may be normal early in disease - normal films do not exclude inflammatory arthritis 2
• Do not obtain MRI acutely - MRI is rarely indicated for emergent cases and should only be considered when surgery is contemplated or pain persists despite adequate conservative treatment 5, 3
• Ultrasound - useful for confirming effusion and guiding aspiration 4, 5

Treatment Approach Based on Most Likely Diagnoses

If Psoriatic Arthritis Suspected (bilateral knees + fingers + plantar/heel pain + skin findings)

• NSAIDs as first-line - naproxen 375-750mg twice daily has been shown effective for inflammatory arthritis with less GI toxicity than aspirin 6
• If inadequate response after 4-6 weeks of NSAIDs, initiate methotrexate - 25mg weekly with 1mg daily folic acid 4
• If methotrexate fails, add TNF-alpha inhibitor - combination therapy dramatically improves both joint and skin disease 4

Critical point: Up to 50% of psoriatic arthritis patients develop progressive joint damage if left untreated, with radiographic damage occurring within 2 years despite clinical improvement 4. Early aggressive treatment prevents disability.

If Viral or Reactive Arthritis Suspected (acute onset, no skin findings)

• Conservative management with NSAIDs - naproxen 375-500mg twice daily 6, 2
• Reassess in 4-6 weeks - viral arthritis and serum sickness are self-limited 2

If Crystal Arthropathy (Gout) Confirmed

• NSAIDs at full anti-inflammatory doses - naproxen 750mg twice daily initially 6
• Expect improvement within 24-48 hours - significant clearing of inflammatory changes should occur 6

Critical Pitfalls to Avoid

• Never administer antibiotics before arthrocentesis if septic arthritis is suspected - this obscures culture results 1
• Do not fail to perform arthrocentesis when effusion is present with signs of infection 1
• Do not overlook psoriatic arthritis - patients may have severe arthritis with minimal skin disease 4
• Do not delay treatment of inflammatory arthritis - radiographic damage can occur within 2 years 4
• Recognize that bilateral knee pain may be referred from hip or spine - always examine hip range of motion 7, 8

When to Refer

• Immediate rheumatology referral if septic arthritis confirmed or suspected 1
• Urgent rheumatology referral if inflammatory arthritis suspected with inadequate response to NSAIDs after 4-6 weeks 4
• Dermatology consultation if psoriatic skin lesions present to optimize combined management 4