Septic arthritis

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]

Septic arthritis
Other namesInfectious arthritis, joint infection
Septic arthritis as seen during arthroscopy[1]
SpecialtyOrthopedic surgery
SymptomsRed, hot, painful single joint[2]
Usual onsetRapid[2]
CausesBacteria, viruses, fungi, parasites[3]
Risk factorsArtificial joint, prior arthritis, diabetes, poor immune function[2]
Diagnostic methodJoint aspiration with culture[2]
Differential diagnosisRheumatoid arthritis, reactive arthritis, osteoarthritis, gout[2][3]
TreatmentAntibiotics, surgery[2]
MedicationVancomycin, ceftriaxone, ceftazidime[2]
Prognosis15% risk of death (treatment), 66% risk of death (without treatment)[2]
Frequency5 per 100,000 per year[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 become 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.[2][4]

Initial treatment typically includes 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 treatment 66% die.[2]

Signs and symptoms

Septic arthritis most commonly causes pain, swelling and warmth at the affected joint.[2][5] Therefore, those affected by septic arthritis will often refuse to use the extremity and prefer to hold the joint rigidly. Fever is also a symptom; however, it is less likely in older people.[6]

On physical examination, the septic joint should be ruled out of intra-articular (from inside the joint) or periarticular (around the joint such as bursa and skin) cause. Intra-articular arthritis usually results in severe limitation of the range of movement of the joint with the joint held in extended position; the joint space will be maximal in this position. In peri-articular arthritis, pain only occurs when the joint is moved, and the lesion usually lies in one specific area around the joint.[2]

The most common joint affected is the knee.[6] Hip, shoulder, wrist and elbow joints are less commonly affected.[7] Spine, sternoclavicular and sacroiliac joints can also be involved. The most common cause of arthritis in these joints is intravenous drug use.[5] Usually, only one joint is affected. More than one joint can be involved if bacteria are spread through the bloodstream.[5]

Prosthetic joint

For those with artificial joint implants, there is a chance of 0.86 to 1.1% of getting infected in a knee joint and 0.3 to 1.7% of getting infected in a hip joint. There are three phases of artificial joint infection: early, delayed and late.[2]

  • Early – infection occurs in less than 3 months. Usual signs and symptoms are fever and joint pain, with redness and warmth over the joint operation site. The mode of infection is during the joint implant surgery. The usual bacteria involved are Staphylococcus aureus and gram negative bacilli.[2]
  • Delayed – infection occurs between 3 and 24 months. There would be persistent joint pain, due to loosening of the implant. The mode of infection is during the implant surgery. Common bacteria are coagulase-negative Staphylococcus and Cutibacterium acnes.[2]
  • Late – more than 24 months. It is usually presented with a sudden onset of joint pain and fever. The mode of infection is through the bloodstream. The bacteria involved are the same as those in septic arthritis of a normal joint.[2]

Cause

Septic arthritis is most commonly caused by a bacterial infection.[8] Bacteria can enter the joint by:

Microorganisms in the blood may come from infections elsewhere in the body such as wound infections, urinary tract infections, meningitis or endocarditis.[7] Sometimes, the infection comes from an unknown location. Joints with preexisting arthritis, such as rheumatoid arthritis, are especially prone to bacterial arthritis spread through the blood.[7] In addition, some treatments for rheumatoid arthritis can also increase a person's risk by causing an immunocompromised state.[2] Intravenous drug use can cause endocarditis that spreads bacteria in the bloodstream and subsequently causes septic arthritis.[2] Bacteria can enter the joint directly from prior surgery, intraarticular injection, trauma or joint prosthesis.[5][9][10]

Risk factors

The rate of septic arthritis varies from 4 to 29 cases per 100,000 person-years, depending on the underlying medical condition and the joint characteristics. For those with a septic joint, 85% of the cases have an underlying medical condition while 59% of them had a previous joint disorder.[2] Having more than one risk factor greatly increases risk of septic arthritis.[7]

Organisms

Most cases of septic arthritis involve only one organism; however, polymicrobial infections can occur, especially after large open injuries to the joint.[10] Septic arthritis is usually caused by bacteria, but may be caused by viral, mycobacterial, and fungal pathogens as well. It can be broadly classified into three groups: non-gonoccocal arthritis, gonococcal arthritis, and others.[2]

  • Non-gonoccocal arthritis – These bacteria account for over 80% of septic arthritis cases and are usually staphyloccoci or streptococci.[2] Such infections most commonly come from drug abuse, cellulitis, abscesses, endocarditis, and chronic osteomyelitis.[2] Methicillin-resistant Staphylococcus aureus (MRSA) may affect 5 to 25% of the cases while gram negative bacilli affects 14 to 19% of the septic arthritis cases. Gram negative infections are usually acquired through urinary tract infections, drug abuse, and skin infections. Old people who are immunocompromised are also prone to get gram negative infections. Common gram negative organisms are: Pseudomonas aeruginosa and Escherichia coli.[2] Both gram positive and gram negative infections are commonly spread through the blood from an infective source; but can be introduced directly into the joint or from surrounding tissue.[5] It often affects older people, and often happens suddenly, involving only one joint. Joint aspiration cultures are positive in 90% of cases, while only 50% of blood cultures yield any organisms.[2]
  • Gonococcal arthritis – Neisseria gonorrhoeae is a common cause of septic arthritis in people who are sexually active and under 40 years old.[2][5] The bacteria is spread through the blood to the joint following sexual transmission. Other symptoms of disseminated gonococcal infection can include migration of joint pain, tenosynovitis and dermatitis.[2][10] Synovial fluid cultures are positive in 25 to 70% of the cases while blood cultures are seldom positive.[2] Apart from blood and joint cultures, swabs from urethra, rectum, pharynx, and cervix should also be taken. Polymerase chain reaction (PCR) is another useful way of identifying gonococcal infections if diagnosis is difficult and clinical presentation is similar to reactive arthritis.[2]
  • Others – Fungal and mycobacterial infections are rare causes of septic arthritis and usually have a slow onset of joint symptoms. Mycobacterial joint infection most commonly affects hip and knee joints, caused by reactivation of past mycobacterial infections, with or without signs and symptoms of tuberculosis in lungs. Synovial fluid cultures will be positive in 80% of the cases. However, acid fast smears are not useful. Histology is not specific to myocobacterial infection as there are other granulomatous diseases that can show similar histology.[2] Borrelia burgdorferi, a bacteria that causes lyme disease, can affect multiple large joints such as knee. Confirmation of Lyme disease is done through enzyme-linked immunosorbent assay (ELISA) followed by confirmation using Western Blot test. It cannot be cultured from synovial fluid. However, PCR testing yields 85% positive result from synovial fluid.[2] Viruses such as rubella, parvovirus B19, chikungunya, and HIV infection can also cause septic arthritis.[5]
  • Prosthetic joint infection – Artificial joint infection are usually caused by coagulase negative Staphylococci, Staphylococcus aureus, and gram negative bacilli. Concurrent infections by multiple organisms is also reported in 20% of the cases. The risk factors of prosthetic joint infections are: previous fracture, seropositive rheumatoid arthritis, obesity, revision arthroplasty, and surgical site infections.[2]

List of organisms
  • Neisseria gonorrhoeae – the most common cause of septic arthritis in young, sexually active adults.[12] Multiple macules or vesicles seen over the trunk are a pathognomonic feature.[13]

Diagnosis
Synovial fluid examination[15][16]
TypeWBC per mm3% neutrophilsViscosityAppearance
Normal<2000HighTransparent
Osteoarthritis<5000<25HighClear yellow
Trauma<10,000<50VariableBloody
Inflammatory2,000-50,00050-80LowCloudy yellow
Septic arthritis>50,000>75LowCloudy yellow
Gonorrhea~10,00060LowCloudy yellow
Tuberculosis~20,00070LowCloudy yellow
Inflammatory = gout, rheumatoid arthritis, rheumatic fever

Septic arthritis should be considered whenever a person has rapid onset pain in a swollen joint, regardless of fever. One or multiple joints can be affected at the same time.[2][5][6]

The diagnosis of septic arthritis is based on physical exam and prompt arthrocentesis which yields synovial fluid from within the affected joint. This fluid should be collected before the administration of antibiotics and should be sent for gram stain, culture, leukocyte count with differential, and crystal studies.[5][7] This can include NAAT testing for N. gonorrhoeae if suspected in a sexually active person.[10]

Other studies such as blood cultures, white blood cell count with differential, ESR, and CRP should also be included. However, white cell count, ESR, and CRP are nonspecific and could be elevated due to infection elsewhere in the body. Serologic studies should be done if lyme disease is suspected.[5][10] Blood cultures can be positive in 25 to 50% of those with septic arthritis due to spread of infection from the blood.[2]

In children, the Kocher criteria is used for diagnosis of septic arthritis.[17]

Joint aspiration
Synovial fluid from a knee with septic arthritis

In the joint fluid, 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);[18] where more than 90% are neutrophils is suggestive of septic arthritis.[2] For those with prosthetic joints, white cell count more than 1,100 per mm3 with neutrophil count greater than 64% is suggestive of septic arthritis.[2] However, septic synovial fluid can have white blood cell counts as low as a few thousand in the early stages. Therefore, differentiation of septic arthritis from other causes is not always possible based on cell counts alone.[7][18] Synovial fluid PCR analysis is useful in finding less common organisms such as Borrelia species. However, measuring protein and glucose levels in joint fluid is not useful for diagnosis.[2]

The Gram stain can rule in the diagnosis of septic arthritis, however, cannot exclude it.[7]

Synovial fluid cultures are positive in over 90% of nongonoccocal arthritis; however, it is possible for the culture to be negative if the person received antibiotics prior to the joint aspiration.[5][7] Cultures are usually negative in gonoccocal arthritis or if fastidious organisms are involved.[5][7]

If the culture is negative or if a gonococcal cause is suspected, NAAT testing of the synovial fluid should be done.[5]

Positive crystal studies do not rule out septic arthritis. Crystal-induced arthritis such as gout can occur at the same time as septic arthritis.[2]

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

Blood tests

Laboratory testing includes white blood cell count, ESR and CRP. These values are usually elevated in those with septic arthritis; however, these can be elevated by other infections or inflammatory conditions and are, therefore, nonspecific.[2][5] Procalcitonin may be more useful than CRP.[19]

Blood cultures can be positive in up to half of people with septic arthritis.[2][7]

Imaging

Imaging such as x-ray, CT, MRI or ultrasound are nonspecific. They can help determine areas of inflammation but cannot confirm septic arthritis.[9]

When septic arthritis is suspected, x-rays should generally be taken.[7] This is used to assess any problems in the surrounding structures[7] such as bone fractures, chondrocalcinosis, and inflammatory arthritis which may predispose to septic arthritis.[2] While x-rays may not be helpful early in the diagnosis/treatment, they may show subtle increase in joint space and tissue swelling.[5] Later findings include joint space narrowing due to destruction of the joint.[9]

Ultrasound is effective at detecting joint effusions.[9]

CT and MRI are not required for diagnosis; but if the diagnosis is unclear or the joints are hard to examine (ie.sacroiliac or hip joints); they can help to assess for inflammation/infection in or around the joint (i.e. Osteomyelitis),[7][9] bone erosions, and bone marrow oedema.[2] Both CT and MRI scans are helpful in guiding arthrocentesis of the joints.[2]

Differential diagnosis

Treatment

Treatment is usually with intravenous antibiotics, analgesia and washout and/or aspiration of the joint.[5][7] Draining the pus from the joint is important and can be done either by needle (arthrocentesis) or opening the joint surgically (arthrotomy).[2]

Empiric antibiotics for suspected bacteria should be started. This should be based on Gram stain of the synovial fluid as well as other clinical findings.[2][5] General guidelines are as follows:

Once cultures are available, antibiotics can be changed to target the specific organism.[5][7] After a good response to intravenous antibiotics, people can be switched to oral antibiotics. The duration of oral antibiotics varies, but is generally for 1–4 weeks depending on the offending organism.[2][5][7] Repeated daily joint aspiration is useful in the treatment of septic arthritis. Every aspirate should be sent for culture, gram stain, white cell count to monitor the progress of the disease. Both open surgery and arthroscopy are helpful in the drainage of the infected joint. During surgery, lysis of the adhesions, drainage of pus, and debridement of the necrtoic tissues are done.[2] Close follow up with physical exam & labs must be done to make sure the person is no longer feverish, pain has resolved, has improved range of motion, and lab values are normalized.[2][7]

In infection of a prosthetic joint, a biofilm is often created on the surface of the prosthesis which is resistant to antibiotics.[20] Surgical debridement is usually indicated in these cases.[2][21] A replacement prosthesis is usually not inserted at the time of removal to allow antibiotics to clear infection of the region.[9][21] People that cannot have surgery may try long-term antibiotic therapy in order to suppress the infection.[9] The use of prophylactic antibiotics before dental, genitourinary, gastrointestinal procedures to prevent infection of the implant is controversial.[2]

Low-quality evidence suggests that the use of corticosteroids may reduce pain and the number of days of antibiotic treatment in children.[22]

Epidemiology

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 treatment 66% die.[2]

Outcomes

Risk of permanent impairment of the joint varies greatly.[7] This usually depends on how quickly treatment is started after symptoms occur as longer lasting infections cause more destruction to the joint. The involved organism, age, preexisting arthritis, and other comorbidities can also increase this risk.[9] Gonococcal arthritis generally does not cause long term impairment.[5][7][9] For those with Staphylococcus aureus septic arthritis, 46 to 50% of the joint function returns after completing antibiotic treatment. In pneumococcal septic arthritis, 95% of the joint function will return if the person survives. One-third of people are at risk of functional impairment (due to amputation, arthrodesis, prosthetic surgery, and deteriorating joint function) if they have an underlying joint disease or a synthetic joint implant.[2] Mortality rates generally range from 10-20%.[9] These rates increase depending on the offending organism, advanced age, and comorbidities such as rheumatoid arthritis.[7][9][10]

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gollark: Defining an array-ish table:```lualocal example_table_name = {1, 2, 3, "hi", {}, "mixed types too"}```Iteration:```lualocal x = {"a", "b", "c"}for index, value in ipairs(x) do print(index, value)end-- prints 1 a then 2 b then 3 c```
gollark: Or more accurately maps which can be used as arrays.
gollark: Tables are basically a combination of maps and arrays for some stupid reason.
gollark: Yes, tables.

References
  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): 21. doi:10.1186/1758-2555-3-21. PMC 3192658. PMID 21961455.
  2. 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.
  3. "Arthritis, Infectious". NORD (National Organization for Rare Disorders). 2009. Archived from the original on 21 February 2017. Retrieved 19 July 2017.
  4. Carpenter, CR; Schuur, JD; Everett, WW; Pines, JM (August 2011). "Evidence-based diagnostics: adult septic arthritis". Academic Emergency Medicine. 18 (8): 781–96. doi:10.1111/j.1553-2712.2011.01121.x. PMC 3229263. PMID 21843213.
  5. Kasper, Dennis L.; Fauci, Anthony S.; Hauser, Stephen L.; Longo, Dan L.; Larry Jameson, J.; Loscalzo, Joseph (2015). "Infectious Arthritis". Harrison's principles of internal medicine. Kasper, Dennis L.,, Fauci, Anthony S., 1940-, Hauser, Stephen L.,, Longo, Dan L. (Dan Louis), 1949-, Jameson, J. Larry,, Loscalzo, Joseph (19th ed.). New York. ISBN 9780071802161. OCLC 893557976.
  6. Margaretten, Mary E.; Kohlwes, Jeffrey; Moore, Dan; Bent, Stephen (2007-04-04). "Does this adult patient have septic arthritis?". JAMA. 297 (13): 1478–1488. doi:10.1001/jama.297.13.1478. ISSN 1538-3598. PMID 17405973.
  7. Goldberg, D.L.; Sexton, D.J. (2017). "Septic arthritis in adults". UpToDate. Waltham, MA: UpToDate Inc.
  8. Shirtliff, Mark E.; Mader, Jon T. (October 2002). "Acute Septic Arthritis". Clinical Microbiology Reviews. 15 (4): 527–544. doi:10.1128/CMR.15.4.527-544.2002. ISSN 0893-8512. PMC 126863. PMID 12364368.
  9. Shirtliff, Mark E.; Mader, Jon T. (2002-10-01). "Acute Septic Arthritis". Clinical Microbiology Reviews. 15 (4): 527–544. doi:10.1128/cmr.15.4.527-544.2002. ISSN 0893-8512. PMC 126863. PMID 12364368.
  10. "Osteomyelitis and Septic Arthritis". Principles and practice of hospital medicine. McKean, Sylvia C.,, Ross, John J. (John James), 1966-, Dressler, Daniel D.,, Scheurer, Danielle (Second ed.). New York: McGraw-Hill Education. 2017. ISBN 9780071843133. OCLC 950203123.CS1 maint: others (link)
  11. 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.
  12. 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.
  13. 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 1752430. 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 1752863. PMID 10364899.
  14. O'Callaghan C, Axford JS (2004). Medicine (2nd ed.). Oxford: Blackwell Science. ISBN 978-0-632-05162-5.
  15. Flynn, John A.; Choi, Michael J.; Wooster, L. Dwight (2013). Oxford American Handbook of Clinical Medicine. OUP USA. p. 400. ISBN 978-0-19-991494-4.
  16. Seidman, Aaron J.; Limaiem, Faten (2019), "Synovial Fluid Analysis", StatPearls, StatPearls Publishing, PMID 30725799, retrieved 2019-12-19
  17. Kocher, Mininder S.; Mandiga, Rahul; Murphy, Jane M.; Goldmann, Donald; Harper, Marvin; Sundel, Robert; Ecklund, Kirsten; Kasser, James R. (June 2003). "A clinical practice guideline for treatment of septic arthritis in children: efficacy in improving process of care and effect on outcome of septic arthritis of the hip". The Journal of Bone and Joint Surgery. American Volume. 85-A (6): 994–999. ISSN 0021-9355. PMID 12783993.
  18. Courtney, Philip; Doherty, Michael (2013). "Joint aspiration and injection and synovial fluid analysis". Best Practice & Research Clinical Rheumatology. 27 (2): 137–169. doi:10.1016/j.berh.2013.02.005. PMID 23731929.
  19. 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.
  20. Berbari, Elie; Baddour, L. M. (2017). "Prosthetic joint infection: Epidemiology, clinical manifestations, and diagnosis". UpToDate. Waltham, MA: UpToDate Inc.
  21. Barbari, Elie; Baddour, L. M. (2017). "Prosthetic joint infection: Treatment". UpToDate. Waltham, MA: UpToDate, Inc.
  22. Delgado-Noguera, Mario F; Forero Delgadillo, Jessica M; Franco, Alexis A; Vazquez, Juan C; Calvache, Jose Andres (2018-11-21). "Corticosteroids for septic arthritis in children". Cochrane Database of Systematic Reviews. 11: CD012125. doi:10.1002/14651858.cd012125.pub2. ISSN 1465-1858. PMC 6517045. PMID 30480764.
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