1. Septic Arthritis
Allison I. Martin, BSN, RN

2. Diagnosis
Septic arthritis is an infection in the joint cavity most often caused by bacteria, but also can be caused by fungi or mycobacteria
Nongonococcal bacteria can lead to irreversible joint damage
Gonococcal bacteria is far less destructive to joints
Acute monoarticular arthritis
Infectious and inflammatory

3. Mechanism of infection
Hematogenous spread
Bacteremia
IV drug abuse
Immunocompromised state (Diabetes, HIV)
Direct inoculation
Recent joint surgery
Prosthetic joint
Steroid injections
Trauma
Spread from local infection
Skin infection or ulcer
Osteomyelitis
Septic bursitis
Abscess
Contaminated joint prosthesis can cause an early or delayed joint infection up to 24 months after surgery. Late infection of a prosthesis is usually due to hematogenous seeding from dental work, skin infection, pneumonia, or UTI
Hematogenous spread or seeding- spread from a remote site of infection, such as UTI, pneumonia, etc

4. Pathogenesis
The synovial fluid within the joint cavity is normally sterile
Synovial tissue has no limiting basement plate so bacteria quickly gain access
Most common causative agents:
Staphylococcus aureus
Streptococcus species
Gram-negative bacilli in immunocompromised and IV drug abusers
Bacteria cause an acute inflammatory cell response in the synovial membrane with purulent effusion into the joint capsule
Following onset, there is a marked hyperplasia of the lining cells in the synovial membrane within 7 days
Inflammatory cells release cytokines and proteases that cause cartilage degradation and inhibit cartilage synthesis leading to rapid destruction of the joint
Gram negative bacilli- E. coli, Proteus mirabilis, Klebsiella, and Enterobacter
Gram negative cocci include Neisseria gonorrheae and Neisseria meningitidis (cause gonococcal arthritis, less destructive)

5. Risk Factors Advanced age (50% of patients are > 60 years)
Diabetes mellitus
Rheumatoid arthritis
Presence of prosthetic joint
Recent joint surgery
Skin infection
Intravenous drug use, alcoholism
Prior intraarticular corticosteroid injection
Bacteremia is more likely to localize in a joint with preexisting arthritis because of damage—osteoarthritis and rheumatoid arthritis
Patients with RA have additional risk factors of maintenance immunosuppressive medications and intraarticular steroid injections
Risk may also be increased in crystal arthropathies

6. Clinical Manifestations
History
Presentation
Monoarticular acute joint swelling, pain, erythema, warmth, joint immobility; ROM is significantly restricted and very painful
Infection in the knee is most common (> 50% of cases), but the hip, shoulder, ankle, elbow, and wrist can also be affected
HPI – OLDCARTS
Onset, location, associated symptoms, risk factors, concurrent illness
Ask about injury or trauma, recent infections of skin or urinary tract
Abrupt onset with fever and chills points to infectious cause
History of skin lesions, vaginal or urethral discharge, exposure to gonorrhea, tick bites or exposure to ticks
Polyarticular diseases may initially present with one acutely inflamed joint or with symptoms that are more pronounced in one joint
Examples: RA, Reiter syndrome, ankylosing spondylitis, psoriatic arthritis, the arthritis of inflammatory bowel disease, and sarcoidosis
Sternoclavicular and sacroiliac joint can be affected in injection drug users
Infection of the hip can manifest as groin pain exacerbated by walking

7. Clinical Manifestations
ROS:
General: fever and chills (common but are absent in up to 20% of cases), fatigue
HEENT: drainage, mucosal ulcers, petechiae in eyes or mouth
Cardiovascular: chest pain, syncope
Respiratory: cough, shortness of breath, dyspnea
GU: urinary symptoms, hematuria, discharge
GI: bowel changes, N/V
Skin: skin wound, lesion, ulcers, bites, petechiae
Musculoskeletal: swelling, erythema, warmth, joint stiffness and immobility (mono-, oligo- or polyarticular)

8. Clinical Manifestations
PMH: Diabetes mellitus, rheumatoid arthritis, gout or pseudogout, prosthetic joint, osteoarthritis, prior intraarticular corticosteroid injections, immunosuppression, HIV infection, previous trauma
PSH: Recent joint surgery (within 24 months), dental procedures
Social history: IV drug abuse, alcoholism, sexual history and STDs (gonococcal arthritis)
Medications: Immunosuppressive therapy, steroids, chemotherapy

9. Physical examination Vitals: Note temperature
Most patients with septic arthritis are febrile with high fever
Patients with gout and rheumatoid arthritis may have low-grade fever
HEENT: Examine eyes for conjunctivitis and iritis, fundi for signs of endocarditis, mouth for mucosal ulcers
Cardiovascular: Auscultate for murmur
Respiratory: Auscultate lungs
Integumentary: Lesions, wounds, ulcers, track marks, tophi
Genitalia: Check for signs of gonococcal urethritis and cervicitis
Musculoskeletal: Examine all joints; assess involved joint for increased warmth, swelling, redness, effusion, and immobility; test active and passive ROM
Differentiate inflammation of the joint space versus periarticular process (tendons, bursa, or skin) which may have preserved ROM despite pain
Check spine ROM, restriction and tenderness can indicate spondylitis
Bacterial arthritis can by the presenting sign of infective endocarditis, listen for murmurs of endocarditis
Skin: also tophi, rheumatoid nodules, pitting of nails and other psoriatic manifestations, erythema nodosum, psoriasis

10. Diagnostic tests
Synovial fluid aspiration is the definitive diagnostic test
Gram stain: gram positive bacteria in about 80% of cases
Culture: positive in 90% of cases with nongonococcal arthritis
Leukocyte count with differential: exceeds 50,000/mcL and often > 100,000/mcL
Crystal analysis
Blood cultures should be obtained (positive in 50% of patients)
CBC: elevated WBCs, common, but not specific
C-reactive protein: 92% sensitive, not specific
Erythrocyte sedimentation rate: 98% sensitive, not specific
Radiographs obtained for baseline image, detect fracture, or underlying inflammatory arthritis
MRI to detect effusions and inflammation in joints that are difficult to examine, including the hip and sacroiliac joints
Ultrasound more sensitive for effusions of the hip
Synovial fluid aspiration is the first choice if an effusion or other signs of inflammation are present
CBC and ESR are moderately helpful in distinguishing inflammatory from noninflammatory when joint fluid cannot be obtained
CRP and ESR are highly sensitive inflammatory markers in septic arthritis, 92% and 98%
Radiographs of infected joint should be obtained to provide a baseline that is useful for comparison during or after treatment to evaluate response to therapy. Also in some cases osteomyelitis or concurrent joint disease may be present.
Omar et al. (2014) – investigated leukocyte esterase and glucose reagent strips to rapidly test synovial fluid for bacterial infection

11. Categories of Synovial Fluid based upon Clinical and Lab Findings
Measure
Normal
Non-inflammatory
Inflammatory
Septic
Volume, mL (knee)
< 3.5
Often > 3.5
Clarity
Transparent
Translucent
Translucent-opaque
Opaque
Color
Clear
Yellow
Yellow to opalescent
Yellow to green, frank pus
Viscosity
High
Low
Variable
WBC, per mm3
< 200
0 to 2000
2000 to 100,000
15,000 to > 100,000
PMNs (%)
< 25
>= 50
>= 75
Culture
Negative
Positive
PMN= Polymorphonuclear leukocytes
In gout and septic joints, the WBC count often exceeds 50,000/mm3
Prosthetic joints with WBCs > 1700/mm3 and neutrophils > 65% are highly sensitive and specific for infection if there is no underlying inflammatory joint disease
Crystal examination under a polarizing lens is the gold standard test for diagnosing gout and pseudogout
Adapted from

12. Differential diagnosis
Inflammatory
Crystal-induced arthritis:
Gout: uric acid crystals
Pseudogout: calcium pyrophosphate crystals
Rheumatoid arthritis
Reactive arthritis
Infectious
Lyme disease
Disseminated Gonorrhea
Non-inflammatory
Hemarthrosis
Red flags
Septic arthritis
Emergency
Immediate hospital admission required
Significant joint destruction and other complications, including amputation, sepsis, and death
Osteomyelitis
Avascular necrosis
RA-

13. treatment
Treatment includes immediate hospitalization for antibiotics and joint drainage
Early consult with orthopedics, rheumatology, and infectious disease
Synovial fluid aspiration analysis, start empirical antibiotics according to gram stain, then tailor antibiotics to culture results
Antibiotic therapy
Gram positive cocci:
Vancomycin (also 1st line for MRSA)
Daptomycin, linezolid, and clindamycin are alternatives
Gram negative bacilli: third-generation cephalosporin
Ceftriaxone, cefotaxime, ceftazidime
Pseudomonas aeruginosa (IV drug abusers)
Ceftazidime and gentamicin
Cephalosporin-allergic patients
Ciprofloxacin and aminoglycoside
Parenteral and oral antibiotic therapy produce adequate drug levels in joint fluid. Intraarticular antibiotics may induce an inflammatory response and are not recommended.
The initial regimen should be tailored to culture and susceptibility results when available

14. Treatment Duration of therapy Joint drainage
Parenteral antibiotics for at least 14 days followed by oral therapy for an additional 14 days
Parenteral antibiotics for 4-7 days followed by days of oral therapy
Three to four weeks of IV therapy may be needed for arthritis caused by P. aeruginosa, Enterobacter spp., S. aureus, or in the setting of bacteremia
Joint drainage
Needle aspiration (arthrocentesis)
Arthroscopic drainage
Arthrotomy (open surgical drainage)
Immobilization, elevation, ice packs
Postpone anti-inflammatory medications for hours; can use analgesics without anti-inflammatories if pain is severe
Early active range of motion as tolerated will speed recovery
Duration of therapy varies and typically depends on the causative agent
Joint drainage should be performed for septic arthritis because this condition represents a closed abscess
Anti-inflammatories delayed so that cultures can grow and arthrocentesis can be repeated if the first result was nondiagnostic

15. Treatment Needle aspiration Arthroscopy Surgical drainage
Knee, perform until culture negative
If not adequate for joint decompression after 3-5 days, then surgical drainage is required
Arthroscopy
Provides easy irrigation and better visualization
Knee, shoulder, wrist
Surgical drainage
Hips, shoulders, and prosthetic joint infections
Any joint not improving after serial needle aspiration or if needle drainage is inadequate

16. outcomes
Prognosis dependent on prior health of the patient, the causative organism, and promptness of treatment
S. aureus is associated with poor functional outcome in 46-50% of cases
Overall mortality rates range from %
Mortality rate increases to 30% for patients with polyarticular sepsis
Morality is 50% if infection due to S. aureus or occurs in the presence of RA
Morbidity occurs in one-third of patients with bacterial arthritis
Amputation, arthrodesis, prosthetic surgery, severe functional deterioration
Failure to initiate appropriate antibiotic therapy within 24 to 48 hours of onset can cause subchondral bone loss and permanent irreversible joint damage and dysfunction
Prompt identification and referral for treatment are imperative
Even with prompt referral and initiation of abx therapy—patient may suffer significant joint destruction
Cormorbid conditions, such as older age, renal or cardiac disease, and concurrent immunosuppression lead to poorer outcome

17. Summary

18. References
Evaluation of acute monoarticular arthritis (2014). In A. H. Goroll & A. G. Mulley (Ed.), Primary care medicine: Office
evaluation and management of the adult patient (7th ed.). Philadelphia: Lippincott Williams & Wilkins.
Goldenberg, D. L., & Sexton, D. J. (2016). Septic arthritis in adults. In Calderwood, S. B.
(Ed.), UpToDate. Retrieved from
Hellman, D. B., & Imboden, J. B. (2015). Nongocococcal acute bacterial (septic) arthritis. In
M. A. Papadakis, S. J. McPhee, & M. W. Rabow (Eds.). Current medical diagnosis & treatment (54th ed., pp ). New York: McGraw-Hill
Horowitz, D. L., Katzap, E., Horowitz, S., & Barilla-LaBarca, M. (2011). Approach to
septic arthritis. American Family Physician. 84(6), Retrieved from
Omar, M., Ettinger, M., Reichling, M., Petri, M., Lichtinghagen, R., Guenther, D.,…Krettek, C. (2014). Preliminary results of a new test
for rapid diagnosis of septic arthritis with use of leukocyte esterase and glucose reagent strips. The Journal of Bone and Joint Surgery. American Volume, 96(24), doi: /JBJS.N.00173

19. Questions?