Septic Arthritis
Pamela Gregory-Fernandez, PA-C
SVCMC PA Education Program
Definition
 Inflammation of a synovial membrane with
purulent effusion into the joint capsule, often
due to bacterial infection
Synonyms
 Bacterial, suppurative, purulent or infectious
arthritis, gonococcal or nongonococcal
A Big Problem
 Despite advances in diagnostic studies,
powerful antibiotics, and early drainage,
significant joint destruction commonly
occurs
 Why?



Lack of clinical suspicion
Delay in definitive diagnostic needle aspiration
Failure to adequately drain the joint
Frequency
 2-10 cases per 100,000 in the general
population
 30-70 cases per 100,000 in patients with
immunological disorders or deficiencies, and
joint replacements
 Gonococcal: women 3x > men
Etiology
 Staph aureus
 Streptococci
 In all age groups, 80% due to gram-positive
aerobes, 20% due to gram-negative anaerobes
 Neonates and infants < 6mos S aureus and gramnegative anaerobes

Incidence of H. influenzae has decreased due to the
vaccine
Pathophysiology
 Adults



Knee 40-50 %
Hip 20-25 %
Infants and young children

Hip 95 %
Infection Sources
 Trauma: direct
 Hematogenous: IV drug injection
 Osteomyelitis adjacent to joint capsule
 Soft tissue infections: cellulitis, abscess,
bursitis, tenosynovitis
Clinical Presentation: “red,
hot, painful joint”
 Fever
 Erythema
 Edema
 Heat
 Pain
 Markedly decreased passive and active ROM
Age Related Presentation
 Young sexually active pts: + fever,
tenosynovitis, migratory polyarthralgia and
dermatitis ( papular rash over trunk and distal
extremity extensor surfaces that may turn
hemorrhagic ) = Suspect N gonorrheae
 IVDU = Pseudomonas
 Infants and young children = difficult
Pediatric Presentation
 Fever, decreased appetite and irritability without
obvious joint involvement is common
 Differentiation from transient synovitis important:
4 independent variables




History of fever
Non-weight-bearing
ESR > 40mm/h
WBC > 12,000/uL
Diagnosis
 Needle aspiration, open drainage and lavage
(arthroscopically or arthrotomy)
Contraindications to arthrocentesis:
1. avoid aspirating from an area that has
overlying soft tissue infection
2. Bleeding disorders
3. Anticoagulation therapy
Lab Studies



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
CBC with diff: leukocytosis and left shift
ESR: monitor treatment
CRP: monitor treatment
Blood cultures: may be + in 50% S aureus
Urethral, cervical , pharyngeal and rectal swabs: N
gonorrheae
 Synovial fluid analysis: Gram stain, culture, cell
count, and crystal analysis
 Synovial Fluid Classification (Modified from
Schumacher HR. Pathologic Findings in
Rheumatoid Arthritis) Quality
 Reference Range
 Noninflammatory
 Inflammatory
 Septic
 Volume, mL
 <3.5
 >3.5