Children - Septic (Infectious) Arthritis

What is septic arthritis?

Septic arthritis is an infection in the joint fluid (synovial fluid) and joint tissues. It occurs more often in children than in adults. The infection usually reaches the joints through the bloodstream. In some cases, joints may become infected due to an injection, surgery, or injury.

What causes septic arthritis?

Different types of bacteria, viruses, and fungi can infect a joint. The types that can cause septic arthritis include:

  • Staphylococci. These are common bacteria that often cause skin infections.
  • Haemophilus influenzae. These are bacteria that can infect the larynx, trachea, and bronchi.
  • Gram-negative bacilli. This is a group of bacteria that includes Escherichia coli, or E. coli.
  • Streptococci. This is a group of bacteria that can lead to a wide variety of diseases.

The most common type of bacteria that causes septic arthritis is called Staphylococcus aureus. It is also known as S. aureus. The bacteria can enter the body in a number of ways, such as:

  • An infection that spreads from another place on the body, such as the skin or genitals
  • An infected wound
  • A broken bone that goes through the skin (open fracture)
  • Foreign object that goes through the skin
  • Injury that breaks the skin

Who is at risk for septic arthritis?

Septic arthritis may occur without any known risk factors. However, children who have an open skin wound and an impaired immune systems due to diabetes, kidney disease, HIV infection, or cancer may be at greater risk of septic arthritis.

What are the symptoms of septic arthritis?

The most common joints affected by septic arthritis are the knee, hip, shoulder, elbow, and wrist. Most often, only one joint is affected. Symptoms can occur a bit differently in each child, but common symptoms include:

  • Fever
  • Joint pain, usually severe
  • Joint swelling
  • Redness in the affected area
  • Warmth around the infected area
  • Limited use of the affected limb, such as refusal to walk
  • Guarding or protecting the affected area to prevent it from being touched or seen
  • Other symptoms of illness, such as vomiting, sore throat, or headache
  • Irritability
  • Loss of appetite

The symptoms of septic arthritis can be like other health conditions. Make sure your child sees his or her healthcare provider for a diagnosis.

How is septic arthritis diagnosed?

Early diagnosis of septic arthritis is important. This is to prevent permanent damage to the joint. The process starts with a medical history and a physical exam. Tests may also be done, such as:

  • Removal of joint fluid. This is done to check for white blood cells and bacteria.
  • Blood tests. These are done to look for bacteria.
  • Phlegm, spinal fluid, and urine tests. These are done to look for bacteria and find the source of infection.
  • X-ray. This is a test that uses a small amount of radiation to create images of internal tissues, bones, and organs.
  • Bone scan. This imaging test uses a tiny amount of radioactive substance to look for arthritis changes in the joints.
  • MRI. This test uses large magnets and a computer to create detailed images of organs and other tissues.
  • Radionuclide scans. These scans use a tiny amount of radioactive substance to look at organs and blood flow to them.


Treatment will depend on your child's symptoms, age, and general health. It will also depend on how severe the condition is.

Septic arthritis often needs treatment right away with antibiotics. This can improve symptoms within 48 hours. Some infections caused by fungi need treatment with antifungal medicine. Viral infections are not treated with medicine.

A fluid called pus may be drained from the joint. Build up of pus can damage the joint. The pus is drained with a needle, tube, or surgery. Other treatment may include:

  • Medicines for pain and fever
  • Physical therapy to keep muscle strength
  • A splint on the joint to relieve pain

What are the complications of septic arthritis?

Septic arthritis can cause joint damage. If the growth plate was affected, this may cause an arm or leg to not grow to the full adult length. The growth plate is the part of the bone where new bone is created. This area of the bone helps determine its final adult length. Make sure to follow up with your child's health care provider to prevent long-term complications.

When should I call my child’s healthcare provider?

If your child’s symptoms get worse or he or she has new symptoms, let the healthcare provider know.

Key points about septic arthritis

  • Septic arthritis is an infection in the joint fluid (synovial fluid) and joint tissues.
  • Different types of bacteria, viruses, and fungi can infect a joint.
  • Symptoms include fever, joint pain, swelling, redness, and warmth.
  • Quick treatment with antibiotics is needed to halt the risk of joint damage.
  • Other treatments include medicines for pain and fever, drainage of the joint, physical therapy, and splints.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Before your visit, write down questions you want answered.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you for your child.
  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.
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