Infectious arthritis is an inflammation of one or more joints that occurs as a result of infection by bacteria, viruses or, less frequently, fungi or parasites. The symptoms of Infectious arthritis depend upon which agent has caused the infection but symptoms often include fever, chills, general weakness, and headaches, followed by inflammation and painful swelling of one or more joints of the body.

Most often, the infection begins at some other location in the body and travels via the bloodstream to the joint. Less commonly, the infection starts in the joint in the course of a surgical procedure, injection or other action.

If septic Arthritis occurs in an artificial joint (prosthetic joint infection), signs and symptoms such as minor Pain and Swelling may develop months or years after knee replacement or hip replacement surgery. Also, a loosening of the joint may occur, which causes Pain while moving the joint or while putting weight on the joint. Typically, the Pain goes away when at rest. In extreme cases, the joint may become dislocated.

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 can develop when an infection, such as a skin 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 — including joint replacement surgery — can give the germs entry into the joint space.

The lining of your joints 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.

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 some 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.

Antibiotics

To select the most effective medication, your doctor must identify the microbe 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 from two to six weeks. Antibiotics carry a risk of side effects, including nausea, vomiting and diarrhea. Allergic reactions also can occur. Ask your doctor about what side effects to expect from your medication.

Removal of replacement joint

If an artificial joint is infected, treatment often involves removing the joint and temporarily replacing it with a joint spacer — a device made with antibiotic cement. Several months later, a new replacement joint is implanted.

If a replacement joint can't be removed, a doctor may clean the joint and remove damaged tissue but keep the artificial joint in place. Intravenous antibiotics are followed by oral antibiotics for several months to prevent the infection from coming back.

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 — can increase your risk of septic arthritis, as can previous joint surgery and joint injury.
• Having an artificial joint. Bacteria can be introduced during joint replacement surgery, or an artificial joint may become infected if germs travel to the joint from a different area of the body through the bloodstream.
• Taking medications for rheumatoid arthritis. People with rheumatoid arthritis have a further increase in risk because of medications they take that can suppress the immune system, making infections more likely to occur. Diagnosing septic arthritis in people with rheumatoid arthritis is difficult because many of the signs and symptoms are similar.
• Skin fragility. Skin that breaks easily and heals poorly can give bacteria 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. People with a weak immune system are at greater risk of septic arthritis. This includes people with diabetes, kidney and liver problems, and those taking drugs that suppress their immune systems.
• Joint trauma. Animal bites, puncture wounds or cuts over a joint can put you at risk of septic arthritis.

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