What is the management for a patient presenting with fever, bilateral knee joint pain, and vomiting?

Management of Fever with Bilateral Knee Joint Pain and Vomiting

Immediate Priority: Rule Out Septic Arthritis

This patient requires urgent diagnostic arthrocentesis of at least one knee joint to rule out septic arthritis, which is a medical emergency that can destroy joints and cause mortality if treatment is delayed. 1, 2

The combination of fever, bilateral large joint involvement (knees), and acute onset strongly suggests either:

• Septic arthritis (bacterial joint infection)
• Reactive arthritis (post-infectious inflammatory arthritis)
• Brucellosis (if exposure history present)
• Systemic infection with polyarticular involvement

Critical Initial Assessment

History Elements to Obtain Immediately

• Recent joint injections - septic arthritis can occur days after intra-articular steroid or hyaluronic acid injections, particularly in elderly patients with comorbidities 3
• Skin infections or recent trauma - direct inoculation routes for bacterial arthritis 4
• Immunosuppression - diabetes, rheumatoid arthritis, immunosuppressive medications, or age >80 years significantly increase septic arthritis risk 1
• Travel history and animal exposure - brucellosis presents with fever and large joint septic arthritis (knees, hips, ankles) and is transmitted through unpasteurized dairy or animal contact 5
• Sexual history - gonococcal arthritis can present with polyarticular involvement 2

Physical Examination Findings

• Pain with passive range of motion is the most sensitive finding for septic arthritis 4
• Joint erythema, warmth, swelling, and effusion - presence of all four increases likelihood of infection 1, 2
• Constitutional symptoms (fever, rigors) are poorly sensitive but when present suggest systemic infection 2
• Lymphadenopathy, hepatosplenomegaly - may indicate brucellosis if exposure history present 5

Immediate Diagnostic Workup

Laboratory Tests (Stat)

• Complete blood count with differential - leukocytosis >10,000/mm³ suggests bacterial infection; pancytopenia may indicate brucellosis 5, 1
• Erythrocyte sedimentation rate and C-reactive protein - elevated in septic arthritis but nonspecific 1
• Blood cultures (before antibiotics) - positive in 25-50% of septic arthritis cases 2
• Comprehensive metabolic panel - assess renal function and liver enzymes 5

Synovial Fluid Analysis (Mandatory)

Arthrocentesis must be performed before initiating antibiotics to obtain synovial fluid for: 1, 2

• Cell count with differential - WBC >50,000/mm³ with >90% neutrophils strongly suggests bacterial infection (in absence of prosthetic joint) 2
• Gram stain - positive in 50-75% of cases, guides initial antibiotic selection 2
• Culture and sensitivity - definitive diagnosis, essential before selecting targeted therapy 2
• Crystal analysis - to exclude gout/pseudogout, though crystal arthropathy and infection can coexist 2

Imaging

• Plain radiographs of both knees - baseline assessment, though limited sensitivity (49%) for acute processes 6
• Ultrasound - can detect joint effusions and guide arthrocentesis 5

Empiric Antibiotic Therapy

Antibiotics should be initiated immediately after synovial fluid is obtained if septic arthritis is clinically suspected. 5, 1

Antibiotic Selection Based on Gram Stain

• Gram-positive cocci: Vancomycin 15-20 mg/kg IV every 8-12 hours 2
• Gram-negative cocci: Ceftriaxone 1-2g IV daily 2
• Gram-negative rods: Ceftazidime 1-2g IV every 8 hours 2
• Negative Gram stain with strong clinical suspicion: Vancomycin PLUS ceftazidime or aminoglycoside 2

Special Considerations

• If brucellosis suspected (animal exposure, unpasteurized dairy, travel to endemic areas): Add doxycycline 100mg PO twice daily plus rifampin 600-900mg daily or gentamicin 5
• Oral antibiotics are not inferior to IV therapy in most septic arthritis cases once organism identified and patient stable 1
• Duration: 2-6 weeks depending on organism and clinical response 1

Source Control

Joint drainage is mandatory in septic arthritis: 2, 7

• Arthroscopic lavage and synovectomy - preferred initial approach for accessible joints like the knee 7, 3
• Open arthrotomy - if arthroscopic drainage inadequate or multiple procedures needed 3
• Serial arthrocentesis - may be sufficient in selected cases with good clinical response 4

Management of Vomiting

• Assess for dehydration - initiate IV fluid resuscitation with normal saline if volume depleted 5
• Anti-emetics - ondansetron or metoclopramide, but monitor QTc interval as these prolong QT 5
• Rule out intra-abdominal pathology - if vomiting persists or abdominal pain develops, consider CT abdomen/pelvis with IV contrast 5

Critical Pitfalls to Avoid

• Delaying arthrocentesis - permanent joint destruction occurs rapidly; synovial fluid must be obtained before antibiotics 1, 2
• Missing bilateral involvement - both knees require assessment; bilateral septic arthritis is rare but possible 5
• Overlooking immunocompromised state - elderly patients and those with diabetes/rheumatoid arthritis have higher mortality risk 1, 3
• Assuming crystal arthropathy - gout and septic arthritis can coexist; always culture synovial fluid 2
• Inadequate source control - antibiotics alone are insufficient; joint drainage is essential 2, 7

Disposition

• Hospital admission required for IV antibiotics, serial joint assessments, and potential surgical intervention 1, 4
• Orthopedic surgery consultation - immediate for joint drainage planning 4
• Infectious disease consultation - if unusual organisms suspected (brucellosis, fungal) or immunocompromised host 5