Septic Arthritis
Septic arthritis is a destructive arthropathy caused by an intra-articular infection that usually is related with severe symptoms such as pain and decreased range of motion. Large weight-bearing joints, particularly the knee, are the most prone to developing septic arthritis.
Septic arthritis due to bacterial infections is commonly classified as either gonococcal or nongonococcal:
|
|
GONOCOCCAL |
NONGONOCOCCAL |
|
Host |
Young, healthy adults |
Small children, elderly, immunocompromised |
|
Pattern |
Migratory polyarthralgias/arthritis |
Monoarthritis |
|
Tenosynovitis |
Common |
Rare |
|
Dermatitis |
Common |
Rare |
|
Positive joint cultures |
<25% |
>95% |
|
Positive blood cultures |
Rare |
40-50% |
|
Outcome |
Good in >95% |
Poor in 30-50% |
Typical clinical manifestations of nongonococcal septic arthritis
An abrupt onset of swelling, warmth, and pain involving one joint is the classic presentation, the exception being an infected joint prosthesis where the presentation may be more indolent (delayed-onset type). Many patients have serious underlying illnesses and may be febrile or have rigors. Large joints (knee, hip) are most commonly involved. Patients keep the knee flexed or hip flexed, abducted, and externally rotated to maximize intracapsular volume. Both passive and active range of motion are very painful.
Predisposing factors:
Impaired host defense (50%)
Neoplastic disease
Elderly (>80 years old) or children (<5 years old)
Chronic, severe illness (i.e., alcoholism, diabetes, cirrhosis, chronic renal disease, human immunodeficiency virus [HIV])
Cutaneous ulcers and skin infections
Sickle cell disease (susceptibility to encapsulated organisms owing to splenic dysfunction)
Hypogammaglobulinemia (susceptibility to Mycoplasmainfections)
Immunosuppressive agents (i.e., glucocorticoids, chemotherapy, biologics)
Direct penetration
Intravenous drug abuse; puncture wounds; invasive procedures
Joint damage
Prosthetic joints (over 50% occur in patients over 70 years old)
Chronic arthritis [i.e., rheumatoid arthritis (RA), hemarthrosis, osteoarthritis]
Host phagocytic defect
Late complement-component deficiencies (susceptibility to Neisseria); impaired chemotaxis
Overall, a causative pathogen is documented by culture in approximately 70% to 90% of septic arthritis patients and include:
|
S. aureus |
44% to 66% (most penicillin-resistant, up to 50% |
|
|
methicillin-resistant [MRSA]) |
|
Group A/B streptococci |
18% to 28% (group B more common in the elderly) |
|
Gram-negative bacilli |
9% to 19% |
|
Streptococcus pneumoniae |
3% |
|
Polymicrobial |
4% |
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