Septic arthritis

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Septic arthritis
Synonyms Infectious arthritis, joint infection
SepticArth2011 (cropped).jpg
Septic arthritis as seen during arthroscopy[1]
Specialty Orthopedic surgery
Symptoms Red, hot, painful single joint[2]
Usual onset Rapid[2]
Causes Bacteria, viruses, fungi, parasites[3]
Risk factors Artificial joint, prior arthritis, diabetes, poor immune function[2]
Diagnostic method Joint aspiration with culture[2]
Similar conditions Rheumatoid arthritis, Reiter’s syndrome, osteoarthritis, gout[2][3]
Treatment Antibiotics, surgery[2]
Medication Vancomycin, ceftriaxone, ceftazidime[2]
Prognosis 15% risk of death (treatment), 66% risk of death (without treatment)[2]
Frequency 5 per 100,000 per year[3]

Septic arthritis, also known as joint infection or infectious arthritis, is the invasion of a joint by an infectious agent resulting in joint inflammation.[3] Symptoms typically include redness, heat, and pain in a single joint associated with a decreased ability to move the joint.[2] Onset is usually rapid.[2] Other symptoms may include fever, weakness, and headache.[2][3] Occasionally more than one joint may be involved.[3]

Causes include bacteria, viruses, fungi, and parasites.[3] Risk factors include an artificial joint, prior arthritis, diabetes, and poor immune function.[2] Most commonly joints becomes infected via the blood but may also become infected via trauma or an infection around the joint.[2] Diagnosis is generally based on aspirating joint fluid and culturing it.[2] White blood cells of greater than 50,000 mm3 or lactate greater than 10 mmol/l in the joint fluid also makes the diagnosis likely.[4][2]

Initial treatment typically include antibiotics such as vancomycin, ceftriaxone, or ceftazidime.[2] Surgery may also be done to clean out the joint.[2] Without early treatment long term joint problems may occur.[2] Septic arthritis occurs in about 5 people per 100,000 each year.[3] It occurs more commonly in older people.[3] With treatment about 15% of people die while without 66% die.[2]

Signs and symptoms[edit]

Septic arthritis can cause pain with any movement of the affected joint. Therefore, those affected by septic arthritis will often refuse to use the extremity and prefer to hold joint rigidly. Other common signs and symptoms are joint swelling, redness, and warmth.


Bacteria are carried by the bloodstream from an infectious focus elsewhere, introduced by a skin lesion that penetrates the joint, or by extension from adjacent tissue (e.g. bone or bursae bovine tb).

Micro-organisms must reach the synovial membrane of a joint. This can happen in any of the following ways:

Bacteria that are commonly found to cause septic arthritis are:

In bacterial infection, Pseudomonas aeruginosa has been found to infect joints, especially in children who have sustained a puncture wound. This bacterium also causes endocarditis.[9]


Septic arthritis should be considered whenever one is assessing a person with rapid onset of joint pain. Usually only one joint is affected[8] however in seeding arthritis, several joints can be affected at the same time; this is especially the case when the infection is caused by staphylococcus or gonococcus bacteria.

The diagnosis of septic arthritis is based on assessment and prompt arthrocentesis. The diagnosis of septic arthritis can be difficult as no test is able to completely rule out the possibility. A number of factors should increase one's suspicion of the presence of an infection. In children these included in Kocher criteria. Diagnosis is by aspiration (giving a turbid, non-viscous fluid), Gram stain and culture of fluid from the joint.

Joint aspiration[edit]

In the joint aspirate, the typical white blood cell count in septic arthritis is over 50,000-100,000 cells per 10−6/l (50,000-100,000 cell/mm3).[10][11] However, septic synovial fluid can have white blood cell counts as low as a few thousand in the early stages and, therefore, differentiation of septic arthritis from aseptic inflammatory arthritis is not always possible based on cell counts alone.[10]

The Gram stain can rule in the diagnosis of septic arthritis, however cannot exclude it.[12]

A lactate level in the synovial fluid of greater than 10 mmol/l makes the diagnosis very likely.[4]

Blood tests[edit]

Laboratory testing (such as a highly elevated neutrophils (approx. 90%), ESR or CRP). The ESR and CRP are almost always raised on admission, CRP being faster in diagnostics.[13] Procalcitonin may be more useful than CRP.[14]

Gonococcal arthritis[edit]

In the case of gonorrhea the knee or wrist may be chronically affected. The pain may be chronic and the physician may inject steroids to reduce symptoms. Weeks later increased pain, redness and swelling- signs of inflammation- appear leading to drainage by needle puncture. Then the gram stain and cultures are typical of a Neisserian infection.

Septic arthritis in a young, sexually active individual may be caused by Neisseria gonorrheae. Gonococcal septic arthritis may present in one of two possible ways:

  • Asymmetric polyarthritis, often associated with tenosynovitis and petechial skin rash
  • Isolated purulent monoarthritis, which in some cases may occur after the asymmetric polyarthritis

Diagnosis is confirmed by gram stain of the synovial fluid, blood cultures and urethral cultures.


X-rays may not be helpful early, but may show subtle increase in joint space tissue swelling. Ultrasound may reveal joint effusion. Imaging can sometimes be used to aid in the diagnosis of septic arthritis. Native X-ray of the joint is neither sensitive nor specific. Ultrasound can detect joint-swelling. MRI findings include: synovial enhancement, perisynovial edema and joint effusion. Signal abnormalities in the bone marrow can indicate a concomitant osteomyelitis. The sensitivity and specificity of MRI for the detection of septic arthritis has been reported to be 67% and 98% respectively.


The term "suppurative arthritis" is a near synonym for septic arthritis. ("Suppurative" refers to the production of pus, without necessarily implying sepsis.)

ICD-10 uses the term "pyogenic arthritis". Pyogenic also refers to the production of pus.

Reactive arthritis refers to arthritis caused by an immune consequence of an infection, but not directly attributable to the infection itself.

Septic arthritis is usually caused by bacteria, but may be caused by viral, mycobacterial, and fungal pathogens as well.[15] A broader term is "infectious arthritis", which describes arthritis caused by any infectious organism.[16] Viruses can cause arthritis,[17] but it can be hard to determine if the arthritis is directly due to the virus or if the arthritis is reactive.[18]

Septic/suppurative arthritis and "bacterial arthritis" are sometimes considered equivalent, but there are exceptions. For example, Borrelia burgdorferi can cause infectious arthritis, but is not associated with suppurative arthritis.[18]


Therapy is usually with intravenous antibiotics, analgesia and washout/aspiration of the joint to dryness. Among pediatric patients with an acute hematogenous septic arthritis a short total course of 10 days of antimicrobials is sufficient in uncomplicated cases.[19]

In infection of a prosthetic joint, a biofilm is often created on the surface of the prosthesis which is resistant to antibiotics. Surgical debridement or arthrotomy is usually indicated in these cases. A replacement prosthesis is usually not inserted at the time of removal to allow antibiotics to clear infection of the region.

Patients in whom surgery is contraindicated may trial long-term antibiotic therapy.[20]

Close follow up with physical exam & labs must be done to make sure patient remain afebrile, pain resolved, improved range of motion and normalized lab values.


  1. ^ Hagino, Tetsuo; Wako, Masanori; Ochiai, Satoshi (1 October 2011). "Arthroscopic washout of the ankle for septic arthritis in a three-month-old boy". Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology. 3 (1). doi:10.1186/1758-2555-3-21. 
  2. ^ a b c d e f g h i j k l m n o p q r s Horowitz, DL; Katzap, E; Horowitz, S; Barilla-LaBarca, ML (15 September 2011). "Approach to septic arthritis". American Family Physician. 84 (6): 653–60. PMID 21916390. 
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  6. ^ a b Kaandorp CJ, Dinant HJ, van de Laar MA, Moens HJ, Prins AP, Dijkmans BA (August 1997). "Incidence and sources of native and prosthetic joint infection: a community based prospective survey". Ann. Rheum. Dis. 56 (8): 470–5. doi:10.1136/ard.56.8.470. PMC 1752430Freely accessible. PMID 9306869. 
    Weston VC, Jones AC, Bradbury N, Fawthrop F, Doherty M (April 1999). "Clinical features and outcome of septic arthritis in a single UK Health District 1982-1991". Ann. Rheum. Dis. 58 (4): 214–9. doi:10.1136/ard.58.4.214. PMC 1752863Freely accessible. PMID 10364899. 
  7. ^ Bowerman SG, Green NE, Mencio GA (August 1997). "Decline of bone and joint infections attributable to haemophilus influenzae type b". Clin. Orthop. Relat. Res. (341): 128–33. PMID 9269165. 
    Peltola H, Kallio MJ, Unkila-Kallio L (May 1998). "Reduced incidence of septic arthritis in children by Haemophilus influenzae type-b vaccination. Implications for treatment". J. Bone Joint Surg. Br. 80 (3): 471–3. doi:10.1302/0301-620X.80B3.8296. PMID 9619939. 
  8. ^ a b Malik S, Chiampas G, Leonard H (November 2010). "Emergent evaluation of injuries to the shoulder, clavicle, and humerus". Emerg Med Clin North Am. 28 (4): 739–63. doi:10.1016/j.emc.2010.06.006. PMID 20971390. 
  9. ^ Topics in Infectious Diseases Newsletter, August 2001, Pseudomonas aeruginosa. Archived 2008-07-24 at the Wayback Machine.
  10. ^ a b Septic Arthritis Aspiration Techniques and Indications for Surgery Archived 2012-04-21 at the Wayback Machine. at Medscape. Author: Nadera Sweiss. Updated: Feb 7, 2012
  11. ^ "Acute Monoarthritis". Egton Medical Information Systems Limited. Archived from the original on 2015-06-27. 
  12. ^ "BestBets: Is a negative gram stain in suspected septic arthritis sufficient to rule out septic arthritis". Archived from the original on 2008-09-02. 
  13. ^ Pääkkönen M, Kallio MJ, Kallio PE, Peltola H (May 2010). "Sensitivity of erythrocyte sedimentation rate and C-reactive protein in childhood bone and joint infections". Clin. Orthop. Relat. Res. 468 (3): 861–6. doi:10.1007/s11999-009-0936-1. PMC 2816763Freely accessible. PMID 19533263. 
  14. ^ Zhao, J; Zhang, S; Zhang, L; Dong, X; Li, J; Wang, Y; Yao, Y (August 2017). "Serum procalcitonin levels as a diagnostic marker for septic arthritis: A meta-analysis". The American journal of emergency medicine. 35 (8): 1166–1171. doi:10.1016/j.ajem.2017.06.014. PMID 28623003. 
  15. ^ Cuéllar ML, Silveira LH, Espinoza LR (May 1992). "Fungal arthritis". Ann. Rheum. Dis. 51 (5): 690–7. doi:10.1136/ard.51.5.690. PMC 1005712Freely accessible. PMID 1616344. 
  16. ^ "infectious arthritis" at Dorland's Medical Dictionary
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  18. ^ a b Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. p. 1310. ISBN 0-7216-0187-1. 
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  20. ^ Prosthetic Joint Infectious Arthritis: Infections of Joints and Bones: Merck Manual Professional [Internet]. [cited 2010 Feb 16];Available from:

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