Septic arthritis (SA) is a joint infection. The joint reacts to it by filling with pus. It may also become swollen.


Bacteria is the most common cause of SA. It attaches to tissue and spreads.

Viruses and fungi can also cause SA. It is not as common.

The infection may be started by an organism:

  • That has entered the blood from an infection somewhere else in the body
  • That entered the bloodstream from IV drug use
  • That is outside the body and entered through a wound or incision from surgery

Joint Damage in Knee

Knee arthitis
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Risk Factors

SSA is more common in older adults and children 2-3 years old.

Here are some factors that may raise your risk:

  • Taking medicines or having diseases that weaken the immune system, such as HIV
  • A history of joint problems or having other types of arthritis
  • A history of IV drug use
  • Long-term health problems, such as diabetes
  • Joint replacement or organ transplant surgery
  • Recent joint injections

Risk factors in children are:

  • Trauma
  • Weakened immune system
  • Respiratory distress syndrome
  • Umbilical artery catheterization
  • History of a urinary tract infection


The knee and hip are the most common site for SA in children. The knee, hip, shoulder, ankle, elbow, and wrist are the most common sites in adults.

Symptoms may include:

  • Adults:
    • Warm, red, painful joint
    • Joint swelling
    • Problems moving the joint or limb
    • Fever
  • Children:
    • Crying when a joint is moved, such as during a diaper change
    • Warmth and redness
    • Swelling
    • Problems moving a joint or limb
    • Problems walking
    • Fever


You will be asked about you or your child’s symptoms and health history. A physical exam will be done. Your doctor may refer you to a specialist.

Body fluids may need to be tested. This can be done with:

  • Testing joint fluids
  • Blood tests

Pictures may be taken of your bodily structures. This can be done with:


Antibiotics are given as soon as SA is found. They are given by IV to start. This helps the joint get medication to kill the bacteria. The medicine you get depends on what is causing your infection. The rest of the antibiotics may be given by mouth.

Fluid may be removed from the joint so it is not harmed. This may be done with a needle or through surgery.

Rest, keeping the joint still, and warm packs may be used for pain. Physical therapy or exercises may also help you get better more quickly.


To lower your chance of SA, get treated for possible infections right away.