Infectious Arthritis

Diagnosis and Empiric Treatment


^^ • Arthrocentesis should be performed as soon as suspected

• Take care not to tap through an >nfected area thus introducing infxn into joint space

• Send fluid for cell count, gram stain, bacterial culture

WBC >50,000 with poly predominance suspicious for bacterial infection (crystals do not rule out septic arthritis!) Initial therapy

• Prompt empiric antibiotics guided by gram stain

• If gram stain negative, empiric coverage w/ ceftriaxone + nafcillin or vancomycin

• Modify antibiotics based on culture results and clinical course

Common microbes


Initial antibiotic regimen

S. aureus (most common)

Normal joints Prosthetic joints Damaged joints

Nafcillin or

Vancomycin if suspect MRSA (eg. hospitalized Pt)


S. epi dermidis

Prosthetic joints Post-joint procedure

Nafcillin or

Vancomycin if suspect MRSA (eg. hospitalized Pt)


Healthy adults Splenic dysfunction

Penicillin G or Ampicillin


Diplococci: N. gonorrheo

Sexually active young adults



Gl infection Immunocompromised

Ceftriaxone - antipseudomonal aminoglycoside if suspect IVDA

Bacterial (Nongonococcal) Epidemiology and risk factors

• Immunocompromised host (eg. diabetics. HIV. elderly. SLE)

• Damaged joints: RA. OA, gout, trauma, prosthetic, prior arthrocentesis (rare)

• Bacterial seeding bacteremia secondary to IVDA. endocarditis, or skin infection direct inoculation or spread from contiguous focus (eg. cellulitis, septic bursitis, osteo) Clinical manifestations

• Acute onset of monoarticular arthritis ( -80%) with pain, swelling, and warmth

• Location: knee (most common), hip. wrist, shoulder, ankle. In IVDA, tends to involve other areas, eg. sacroiliac joint, symphysis pubis, sternoclavicular and manubrial joints.

• Constitutional symptoms: fevers, chills, sweats, malaise, myalgias, pain

• Infection can track from initial site to form fistulae. abscesses, or osteomyelitis

• Septic bursitis must be differentiated from septic intra-articular effusion Additional diagnostic studies

• Synovial fluid: WBC usually >100,000 (but can be as low as 1000). >90% polys gram stain © in 75% of Staph, 50% of GNR: culture © in >90% of cases

• Leukocytosis with left shift

• Conventional radiographs usually normal until after 2 wks of infection when bony erosions, joint space narrowing, osteomyelitis, periostitis can be seen

• CT and MRI useful especially for suspected hip infection or epidural abscess Definitive treatment

• Antibiotics

• Surgical drainage/lavage indicated in many cases, especially for larger (oints

• Prognosis: 10-50% mortality depending on virulence of organism, time to Rx. host s_✓

Disseminated Gonococcal Infection (DGI)


• Most frequent type of infectious arthritis in sexually active young adults

• Caused by Neisseria gonorrhea

• Normal host as well as Pts w/ deficiencies of terminal components of complement

• Female:male ratio 4:1. t incidence during menses, pregnancy and postpartum period.

T incidence in homosexual males. Rare after age 40.

Clinical manifestations

• Preceded by mucosal infection (eg. endocervix. urethra, or pharynx) that is often asx

• Usually presents as two distinct syndromes:

Joint localized: purulent arthritis (40%) usually of knees, wrists, hands, or ankles Bacteremia: triad of polyarthritis, tenosynovitis, skin lesions prodrome: fever, malaise, migratory polyarthralgias (wrist, knees, ankles, elbows) acute onset of tenosynovitis (60%) in wrists, fingers, ankles, toes rash ( >50%): gunmetal gray pustules with erythematous base on extremities & trunk

• Rare complications: Fitz-Hugh Curtis (perihepatitis), pericarditis, meningitis.

myocarditis, osteomyelitis

Additional diagnostic studies

• Leukocytosis with left shift; t ESR

• Synovial fluid: WBC >50,000 (but can be <10.000). poly predominant

Gram stain © in - 25% of cases culture © in up to 50% of cases if culture anaerobically on Thayer-Martin media PCR for gonococcal DNA can improve Se (not yet widely available)

• Blood culture: more likely © in tenosynovitis; rarely in joint localized disease

• Gram stain and culture of skin lesions occasionally ©

• Cervical, urethral, pharyngeal, rectal cultures on Thayer-Martin media indicated; check for



• Ceftriaxone x 7 d w/ empiric doxycydine for possible concurrent Chlamydia

• Joint aspiration or arthroscopyyiavage may be required for Pts with purulent arthritis

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