Septic arthritis: Infection of the knee joint

27 February 2016
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27 February 2016, Comments: 0

An individual can end up with knee joint infection due to various causes. Always bear in mind that the knee joint is highly complex and comprised of cartilage, ligaments and other structures that facilitate movement. The fluid in the knee has a tendency to be infected which is called septic arthritis. The knee is the usual site for joint infections.

Indications of septic arthritis

The indications of septic arthritis include intense joint pain, high body temperature or fever, swelling, redness and warmth of the skin and limited joint movement. There are some individuals who initially notice fluid in the joint or effusion. Children who develop joint infections also appear sick, have poor appetite and irritable.

What are the causes?

There are various ways in which bacteria can spread into the joint space and trigger septic arthritis such as the following:

  • Direct penetrating trauma on the knee
  • Bacterial infection via the bloodstream or bacteremia
  • Spread of infection close to the knee

Other potential risk factors for septic arthritis include conditions that weaken the immune system, diabetes and conditions that affect the joints such as rheumatoid arthritis.

Septic arthritis

Septic arthritis is managed by draining the fluid in the joint space along with antibiotics.

Diagnosing septic arthritis

Assessment of fluid in the knee is vital in determining the diagnosis of septic arthritis as well as identifying the causative bacteria. The doctor will utilize a needle that is introduced into the patella and the fluid is aspirated. The fluid is sent to the laboratory for culture to check if bacteria grows as well as check the level of white blood cell count which is an indicator for infection.

Other tests that the doctor will request include MRI of the joint that can distinguish if there is a complementary bone infection as well as blood culture to check for the existence of bacteria in the bloodstream.


Septic arthritis is managed by draining the fluid in the joint space along with antibiotics. The drainage helps reduce the pressure in the joint as well as allow identification of the causative bacteria. Initially, the treatment involves broad-spectrum intravenous antibiotics to eliminate a wide variety of bacteria.

If the bacterium is identified, the treatment can be changed to oral antibiotics. In case the causative bacterium is not identified, an extended course of intravenous antibiotics might be required to eliminate the infection.

Early identification and management of septic arthritis is vital to prevent any long-term complications. If the condition is not treated, it can progress to chronic joint inflammation and deformity of the knee that can cause difficulty walking as well as limitations on leg movement.

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