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Septic arthritis

Definition

Septic arthritis is an intensely painful infection in a joint. The joint can become infected with germs that travel through your bloodstream from another part of your body. Septic arthritis can also occur when a penetrating injury brings germs directly into the joint.

Infants and older adults are most likely to develop septic arthritis. The most common joints affected are the knees and hips. Septic arthritis can quickly and severely damage the cartilage and bone within the joint, so prompt treatment is crucial.

Treatment involves draining the joint with a needle or via an operation. Intravenous antibiotics also may be necessary to stop the infection.

Symptoms

Septic arthritis typically causes extreme discomfort and difficulty using the affected joint. The joint may be swollen, red and warm, and you might have a fever.

When to see a doctor
See your doctor if you have sudden onset of severe pain in a joint. Prompt treatment may help minimize joint damage.

Causes

Septic arthritis can be caused by bacterial, viral or fungal infections. Bacterial infection with Staphylococcus aureus (staph) is the most common cause. Staph commonly lives on even healthy skin.

Septic arthritis may develop when an infection elsewhere in your body, such as an upper respiratory tract infection or urinary tract infection, spreads through your bloodstream to a joint. Less commonly, a puncture wound, drug injection or surgery in or near a joint may give the germs a pathway into the joint space.

The lining of your joints (synovium) has little ability to protect itself from infection. Your body's reaction to the infection including inflammation that can increase pressure and reduce blood flow within the joint contributes to the damage.

Risk factors

Risk factors for septic arthritis include:

  • Existing joint problems. Chronic diseases and conditions that affect your joints such as osteoarthritis, gout, rheumatoid arthritis or lupus may increase your risk of septic arthritis. An artificial joint, previous joint surgery and joint injury also increase your risk.
  • Taking medications for rheumatoid arthritis. People with rheumatoid arthritis have a further increase in risk because of the medications they take. Rheumatoid arthritis medications may suppress the immune system, making infections more likely to occur. Also, diagnosing septic arthritis in people with rheumatoid arthritis is difficult because many of the signs and symptoms are similar.
  • Skin fragility. If your skin breaks easily and heals poorly, bacteria may have constant access to your body. Skin conditions such as psoriasis and eczema increase your risk of septic arthritis, as do infected skin wounds. People who regularly inject drugs also have a higher risk of infection at the site of injection.
  • Weak immune system. A weak immune system may give you a higher risk of septic arthritis because your body can't defend itself against infections. People with diabetes, kidney and liver problems, and those taking drugs that suppress their immune system have an increased risk of infections.

Having a combination of risk factors usually puts you at a greater risk than having just one risk factor.

Complications

If treatment is delayed, septic arthritis can quickly lead to joint degeneration and permanent damage.

Preparing for your appointment

If you have painful and inflamed joints, you're likely to start by seeing your family doctor. He or she may refer you to an infectious disease or joint specialist.

Because appointments can be brief and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Write down key personal information, including other medical conditions you may have and any recent infections.
  • Make a list of all medications, as well as any vitamins or supplements, that you're taking.
  • Take a family member or friend along, if possible. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor.

List your questions from most important to least important in case time runs out. For septic arthritis, some basic questions to ask your doctor include:

  • What is likely causing my symptoms or condition?
  • Are there any other possible causes?
  • Do I need any tests to confirm the diagnosis?
  • What treatment approach do you recommend?
  • How soon do you expect my symptoms to improve with treatment?
  • Is there anything I can do now to help relieve my joint pain?
  • Am I at risk of long-term complications from this condition?
  • When should I be seen for a follow-up exam?
  • I have these other health conditions. How can I best manage them together?
  • Should I see a specialist?
  • Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • What are your symptoms, and when did you first notice them?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?
  • Have you had any recent infections?
  • Do you have any chronic illnesses?
  • What medications are you currently taking, including vitamins and supplements?
  • Have you ever had joint surgery or joint replacement?
  • Do you use recreational drugs?

Tests and diagnosis

The following tests typically help diagnose septic arthritis:

  • Joint fluid analysis. To discover exactly what bacterium is causing your infection, your doctor usually takes a sample of the fluid within your joint (synovial fluid) through a needle inserted in the space around your joint. Synovial fluid normally appears clear and thick. Bacterial infections can alter the color, consistency, volume and makeup of the synovial fluid. Lab analysis of your synovial fluid iincludes tests to determine what organism is causing your infection.
  • Blood tests. Your doctor may order blood tests to see if bacteria are present in your bloodstream.
  • Imaging tests. X-rays and other imaging tests of the affected joint also may be ordered to assess any damage to the joint.

Treatments and drugs

Doctors rely on joint drainage and antibiotic drugs to treat septic arthritis.

Joint drainage
Removing the infected joint fluid is crucial. Drainage methods include:

  • Needle. In many cases, your doctor can withdraw the infected fluid with a needle inserted into the joint space.
  • Scope procedure. In arthroscopy (ahr-THROS-kuh-pee), a flexible tube with a video camera at its tip is placed in your joint through a small incision. Suction and drainage tubes are then inserted through small incisions around your joint.
  • Open surgery. Some joints, such as the hip, are more difficult to drain with a needle or arthroscopy, so an open surgical procedure might be necessary.

Antibiotic drugs
To select the most effective medication, your doctor must identify the specific microbe that's causing your infection. Antibiotics are usually given through a vein in your arm at first. Later, you may be able to switch to oral antibiotics. Typically, treatment lasts about two to six weeks. Antibiotics carry a risk of side effects, including nausea, vomiting and diarrhea. Allergic reactions also can occur. Talk to your doctor about the side effects to expect from your specific medication.

Updated: 1/17/2013

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