Septic arthritis, infectious arthritis 3.5/5 (6)

Share Button
Septic Knee Arthritis, Caused by Tuberculosis: Lynn MM, 2012. Rheumatology Department, Queen Elisabeth Hospital, London, UK. CC BY 2.0


Septic arthritis / infectious arthritis is arthritis (Arthritis) caused by bacteria or other microorganisms. Infections of the vertebrae are termed Pyogen vertebral osteomyelitis and infection of intervertebral discs such as disk. Septic arthritis is devastating compared to other forms of arthritis, and therefore early diagnosis and treatment are especially important.


The number who have septic arthritis (prevalence) is estimated at 2-10 / 100.000 in Western Europe, but significantly depends on risk factors (reference: Mathews CJ, 2010). The incidence is significantly higher among rheumatologists who have prosthetic joints (Mathews CJ, Lancet. 2010). Bacterial arthritis after intra-articular steroid injection performed by experienced doctors has a low infection rate (septic / infectious arthritis) of 0,037% -0,01% (Geirsson AJ; Hartmann H, 2000). Among children, the incidence is highest at 2-3 years of age. 

Disease Cause

The most common in septic arthritis is that bacteria spread via the blood from another infection and migrate from the blood into one (rarely more) joint. Less often, bacteria enter from skin, wounds or stings.

Risk factors for septic arthritis

  • Age over 80 years
  • Osteoarthritis
  • Bacteria in wounds and skin in other infections
  • Diabetes mellitus (diabetes)
  • HIV infection
  • Immunosuppressants (cortisone, biologics, other DMARDs)
  • Injections in joints
  • Intravenous substance abuse
  • Surgical intervention
  • Liver disease, chronic
  • Prosthetic joints
  • Rheumatic disease, chronic as in Arthritis, RA where the risk 4-15 doubled
  • Sexual partners, alternating (gonococci)
  • venous Catheters

(reference: Horowitz DL, 2011)

Bacteria and other microorganisms

Bacteria are the cause of septic arthritis for approx. 80% of cases. The most common cause in adults in Europe is the bacterium Staphylococcus aureus (S. aureus). Among children aged 6-36 months, the bacterium Kingella kingae the most common cause of infectious arthritis and osteomyelitis. In neonates, group B streptococci, staphylococcus aureus, neisseria gonorrhea and gram-negative bacteria are seen.. Staphylococci have their own ability to infect joints. They can form a biofilm in the infected joint, making it difficult to get rid of the infection. Rare bacteria are streptococci, gonorrhea, Lyme disease (after being bitten by a tick), Tuberculosis (often little pain, but great damage to the joint).


The general condition is usually affected, so night sweats, fever and frostbite are typical. With a weakened immune system (high doses of cortisone, other immunosuppressive drugs or old age) the symptoms may be less obvious.

One joint commonly attacked (monoarthritis) and knee (> 50%), hip, ankle, shoulder or wrist are most exposed outside the spine (vertebral osteomyelitis, discitis). Prosthetic joints can also become infected.

Dan infected joint is characterized by severe pain, so that one can not strain. The skin over the joint is warmer than the surroundings and sometimes also red. Swelling can be seen or felt.


Medical history includes predisposing factors and typical symptoms (see above).

Clinical examination reveals one (rarely more) painful, hot, head joint with impaired mobility and affected general condition. Signs of infections in other organs that may be the starting point and other predisposing disease are considered.

Blood tests shows remarkably high CRP (often> 200 mg / L) and high lowering reaction (SR). High numbers of white blood cells (leukocytes) with the subgroup neutrophils strengthen the suspicion.

Urin test examined to rule out urinary tract infection as a possible trigger (urosepsis).

Imaging. MRI scans show signs of arthritis and cartilage damage combined with more marked bone marrow edema than in non-infectious arthritis. X-rays or CT images can show remarkably rapidly developing destruction of bone tissue at the joint. Suspected skeletal injuries are also detected in the back.

Joint fluid examination under a microscope, by cultivation and other special undergrowths. Suspicion is due to the medical history and the detection of a high number of leukocytes in synovial fluid (> 50), typically with a predominance of neutrophils. The synovial fluid is often stained and not very viscous.


The diagnosis is based on the medical history and examinations as described above. About 50% have bacteria in the blood. Joint fluid and blood samples for the detection of bacteria are essential and should be sought before antibiotics are given.

Incorrect diagnosis, Similar conditions, Differential diagnoses


Antibiotics given intravenously are most often needed. Treatment over 3-8 weeks may be necessary, even longer if the spine is affected. In addition, the affected joint may need to be rinsed and drained repeatedly. This is usually done in the department of orthopedics. In tuberculous arthritis, treatment is usually done in collaboration with a specialist in infectious disease or lung diseases. Children with septic arthritis are treated by a pediatrician.


Infectious arthritis can lead to potentially life-threatening complications in the lining of bacterial skeletal infection (osteomyelitis) and spread to other organs via the blood. Without antibiotics, two out of three patients die with infectious arthritis. Elderly people and people with weakened immune systems for other reasons are most at risk. With recommended treatment, mortality is low. After completion of antibiotic treatment, up to 50% regain their joint function after infection with S. aureus. Better results are seen after pneumococcal infection where 95% regain function.

Guidelines / recommendations

EULAR 2016 (Combe B, Management early arthritis)

ACR 2017 (Ringhold S, 2017; JIA and tuberculosis)

International 2014 (Inanone F, 2014)

Norwegian Rheumatological Association


This page has had 1 visits today

Please rate this page