Health Library

Septic 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.
  • Gonococci. This is the bacterium that causes gonorrhea.
  • Viruses. Viruses such as HIV can infect the joints of people of all ages.

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?

Risk factors for septic arthritis include:

  • Past history of septic arthritis
  • IV drug use
  • Rheumatoid arthritis
  • Osteoarthritis
  • A systemic blood-borne infection

Other factors that may increase the risk for septic arthritis include:

  • Diabetes
  • Lung or liver disorders
  • Old age
  • Alcoholism
  • HIV
  • A suppressed immune system

What are the symptoms of septic arthritis?

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

  • Fever
  • Joint pain
  • Joint swelling

The symptoms of septic arthritis can be like other health conditions. Make sure you see your health care 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.

How is septic arthritis treated?

Treatment will depend on your 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. A buildup of pus can damage the joint. The pus is drained with a needle, tube, or surgery. Other treatment may include:

  • Medications 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 destroy the joint cartilage. This can cause permanent damage to the joint.

When should I call my health care provider?

If your symptoms get worse or you have new symptoms, let your health care 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 a splint.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
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