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updated July 28, 2010

Septic arthritis

Filed under: Boomer's Health
Septic arthritis is an intensely painful infection in a joint. Bacteria, or less commonly fungi, can spread from other infected areas in your body to a joint. Sometimes bacteria infect only the joint, leaving other areas of your body unharmed.

In septic arthritis, germs infiltrate your joint — usually just one — and damage it, causing severe pain, warmth and swelling. Bacteria most commonly target your knee, though other joints can be affected by septic arthritis, including your ankle, hip, wrist, elbow and shoulder.

Young children and older adults are most likely to develop septic arthritis. If treated within a week after symptoms first appear, most people make a complete recovery.

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Septic arthritis typically causes extreme discomfort and difficulty using the affected joint. Signs and symptoms may include:

  • Fever
  • Severe pain in the affected joint, especially when you move that joint
  • Swelling of the affected joint
  • Warmth in the area of the affected joint

In children, additional symptoms may include:

  • Poor appetite
  • Malaise
  • Rapid heartbeat (tachycardia)
  • Irritability

If you're taking medications for other types of arthritis, you may not feel severe pain with septic arthritis because those medications may mask the pain and fever.

In adults, the joints of the arms and legs — especially the knees — are most commonly affected by septic arthritis.

In children, the hip is the joint most likely to be affected. Children with septic arthritis of the hip often hold their hip in a fixed position and try to avoid any joint rotation.

In rare cases other joints, such as those in the back, neck and head, may be affected.

When to see a doctor
See your doctor if you have signs and symptoms that may indicate septic arthritis, such as sudden onset of severe pain in a joint. If you're at an increased risk of infection and you notice signs and symptoms of infection, such as fever and chills, see your doctor right away. Prompt treatment may prevent the spread of infection and minimize the damage to your affected joint.

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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 near a joint may allow bacteria into the joint space.

The lining of your joints (synovium) has little to protect itself from infection. Once bacteria reach the synovium, they enter easily and can begin destroying cartilage. Your body's reaction to the bacteria — including inflammation around the joint, increased pressure in your joint and reduced blood flow to the joint — contributes to the damage of your joint.

Types of bacteria
A number of strains of bacteria can cause septic arthritis. The most common type involved in septic arthritis is Staphylococcus aureus (staph) — a type of bacteria commonly found on your skin and in your nose.

In the past, septic arthritis was more frequently caused by the bacterium that causes the sexually transmitted disease gonorrhea. But use of safer sex practices has led to a decline in gonorrhea and its complications, including septic arthritis. Still, in younger sexually active people, gonorrhea is a potential cause of septic arthritis.

Other infectious causes of arthritis
Bacteria are just one cause of joint infections. Viruses also can attack joints (viral arthritis), though this condition usually resolves on its own and causes little joint damage. In rare cases, joint infections can be caused by a fungus (fungal arthritis). Another infectious type of arthritis is reactive arthritis, which causes joint pain in response to an infection in another part of the body, though the joint itself isn't infected.

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Risk factors for septic arthritis include:

  • Existing joint problems. Diseases and conditions that affect your joints — including other types of arthritis, gout, pseudogout and lupus — may increase your risk of septic arthritis. An artificial (prosthetic) 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 systems (immunosuppressive drugs) 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.

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Prompt treatment with antibiotics combined with drainage of fluid from the joint usually resolves the infection. If treatment is delayed, however, the infection can quickly lead to joint degeneration and permanent damage.

Complications of septic arthritis often include:

  • Osteoarthritis
  • Joint deformity

In severe cases, the joint may need to be surgically reconstructed. If the infection affects a prosthetic joint, the prosthetic joint may need to be replaced.

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If you have painful and inflamed joints, you're likely to start by seeing your primary care doctor or a general practitioner. However, in some cases you may be referred to an infectious disease or joint specialist. If you've been seeing a joint specialist for an existing condition such as arthritis, you may start by seeing this doctor first.

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?

What you can do in the meantime
Avoid activities that seem to make your symptoms worse. To ease joint pain, try resting your affected joint and applying warm compresses. Pain relievers, such as ibuprofen (Advil, Motrin, others) and aspirin, also may help.

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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.

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Doctors rely on antibiotic drugs and joint drainage when treating septic arthritis.

Antibiotic drugs
Your doctor must identify the bacterium that's causing your infection, and then select the most effective antibiotic to target that specific bacterium. Antibiotics are usually given through a vein in your arm (intravenously) at first. Later, in some cases, you may be able to switch to oral antibiotics. How long you undergo antibiotic treatment depends on your health, the type of bacterium you're infected with and the extent of the infection. 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.

Joint drainage
Draining the infected synovial fluid from your joint serves three purposes: It removes bacteria from your joint, reduces pressure on your joint, and gives your doctor a sample to test for bacteria and other organisms. The most common method of removing joint fluid is through arthroscopy (ahr-THROS-skuh-pee). In arthroscopy, 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 to siphon off infected synovial fluid.

Your doctor may be able to remove fluid from your joint with a needle (arthrocentesis). Arthrocentesis may be repeated, usually daily, until no bacteria are found in the extracted fluid. Hip joints, which are difficult to access, may require open surgery for fluid drainage. Repeat surgery is sometimes necessary.

Once the infection is under control, your doctor may recommend gentle movement to keep your joint functional. Motion can keep your joint from becoming stiff and your muscles from becoming weak. Movement also encourages blood flow and circulation, which helps your body's healing process.

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If you've been diagnosed with septic arthritis, self-care measures may help you feel better during treatment. Here are some suggestions:

  • Follow your doctor's instruction for exercising your affected joint.
  • With your doctor's permission, engage in low-impact activities.
  • Use nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin, others) or aspirin, to ease joint pain. Resting the affected joint and applying warm compresses also may help relieve pain and inflammation.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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