Septic arthritis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 9, 2016
StartDiseasesSeptic arthritis

Septic arthritis, also known as infectious arthritis is an infection of the joint that is caused by germs or other microorganisms. When joint fluid is contaminated through contact with bacteria, viruses, or fungi, it loses its ability to properly lubricate the joint. This causes pain and can lead to lasting damage to the cartilage and bone within the joint, necessitating immediate medical attention and often surgical drainage of the joint fluid. 


Definition & Facts

Septic arthritis can be caused by a variety of microorganisms. Infants and the elderly are most susceptible to septic arthritis, just as they are more susceptible to more traditional infections. Although this type of arthritis mainly occurs in one large joint of the body, there are rarer cases where it affects several different joints simultaneously.

Septic arthritis commonly affects knees, but can also occur in hips, shoulders, and ankles. The condition causes inflammation of the joint and extreme discomfort in those affected. Infectious arthritis is relatively easy to diagnose, but related health problems often crop up and complicate recovery and surgery

Symptoms & Complaints

A great deal of pain is a major symptom. Joint swelling and high grade fever are also major symptoms. Chills, general fatigue and weakness, and increased warmth in the joint are secondary symptoms. The increased warmth occurs because of a rapid increase in blood flow to the impacted area, a consequence of the body's effort to fight the infection.

The joint itself will also be red and stiff, and the patient will typically experience difficulty attempting to bend or otherwise move the limb or appendage.

These symptoms tend to occur in large joints such as the knee or elbow, but patients should not rule similar symptoms out if they are occurring in smaller joints. Patients with previous risk factors, and those experiencing infection by unusual microbes, could experience these symptoms in fingers, collarbones, or even breast bones


The three main causes of septic arthritis are contact with bacteria, viruses, or fungi. The most common cause of this type of arthritic problem is the onset of a staph infection, caused by the bacteria, Staphylococcus aureus. Staph bacteria exist on the surface of healthy skin but can cause serious problems if they find their way into joint fluid and cause infection.

Other bacteria that can cause infection include streptococcus and Haemophilius influenza. Most bacterial infections are the result of contaminated open wounds or even contamination during joint surgery. Any bacteria that enter the bloodstream, even from an unrelated infection like a urinary tract infection, could cause joint inflammation. 

Viruses and fungal infections can also lead to septic arthritis, although these instances are considered rarer. Viral infections such as hepatitis A, hepatitis B, and hepatitis C, the mumps, HIV, and the herpes virus infection can all cause septic arthritis if they are treated improperly. Histoplasmosis and blastomyocis are two fungal infections that can cause septic arthritis. Although these infections are typically slower to develop than bacterial infections, they are still harmful to an individual's joints. 

Diagnosis & Tests

Doctors usually are able to detect the presence of septic arthritis by using physical examination techniques, but most doctors will administer a series of tests rather than diagnose purely by eye. A joint fluid analysis technique called arthrocentesis is the most common test employed by doctors in this situation. In this procedure, the joint is punctured surgically by a needle and the fluid is examined under a microscope so that the doctor can determine which microbe is causing the infection. Close examination of the joint fluid, also called synovial fluid, allows the doctor to prescribe the correct medicine to the patient.

Less commonly, blood tests or imaging tests are used to determine the cause of the infection. Imaging tests are mainly used to determine the extent of the damage to the joint, so that doctors can assess if surgery would be necessary, and if so, which specific surgical approaches would be appropriate. 

Treatment & Therapy

Doctors use a dual treatment approach to combat septic arthritis. Traditional methods pair joint fluid drainage with powerful antibiotic drugs, designed to both combat the spread of the infection and clear the joint of contaminated fluid. Joint drainage can be accomplished in several different ways: by using a needle, by utilizing arthroscopic methods and placing delicate suction tubes into small cuts around the joint, or by performing open surgery on the affected area. 

Even before the joint is drained, antibiotics will be administered to the impacted region. There are several different antibiotic regimens, and doctors must choose the most appropriate one based on whether or not the infection is caused by bacteria, and if so, which kind of bacteria. Antibiotics are administered intravenously initially at the hospital, then orally at home.

Despite the power of many modern antibiotics, it still typically takes anywhere from four to six weeks of consistent treatment to rid the body and joint of infection. Even if a precise cause of infection cannot be ascertained, the doctor can prescribe antibiotics that are capable of treating a wide array of infections. Side effects, including nausea or allergic reactions, are possible during the course of treatment. 

Prevention & Prophylaxis

Septic arthritis is difficult to prevent because it arises as the result of persistent infectious microbes. Patients at risk are advised to avoid puncture wounds or other damage to the skin. There are a number of risk behaviors that should be avoided if one is worried about septic arthritis. These behaviors include IV drug use and unprotected sex.

Individuals should also recognize if they are already susceptible to septic arthritis due to pre-existing conditions. People with immunodeficiency disorders, cancer, and diabetes are at a high risk for joint infection, and should exercise proper caution and joint care. Visiting the doctor immediately after the onset of severe pain in a joint is important in that it allows for quick administration of medication.