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Infectious Arthritis

(Septic Arthritis)


Steven Schmitt

, MD, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University

Last full review/revision Jun 2022| Content last modified Sep 2022

Infectious arthritis is infection in the fluid and tissues of a joint usually caused by bacteria but occasionally by viruses or fungi.

  • Bacteria, viruses, or fungi may spread through the bloodstream or from a nearby infection into a joint, causing infection.

  • Pain, swelling, and fever usually develop within hours or a couple of days.

  • Joint fluid is withdrawn with a needle and tested.

  • Antibiotics are begun immediately.

There are two types of infectious arthritis:

  • Acute

  • Chronic

Acute infectious arthritis

Acute infectious arthritis that is caused by bacteria begins quickly. Most cases of infectious arthritis are acute. Acute infectious arthritis can affect healthy people as well as people who have risk factors Acute infectious arthritis Infectious arthritis is infection in the fluid and tissues of a joint usually caused by bacteria but occasionally by viruses or fungi. Bacteria, viruses, or fungi may spread through the bloodstream... read more . Cartilage within the joint, which is essential for normal joint function, can be destroyed or damaged within hours or days.

Sometimes, arthritis develops in people who have infections that do not involve the bones or joints, such as infections of the genital organs or digestive organs. This type of arthritis is a reaction to that infection and so is called reactive arthritis Reactive Arthritis Reactive arthritis (previously called Reiter syndrome) is a spondyloarthritis causing inflammation of the joints and tendon attachments at the joints, often related to an infection. Joint pain... read more Reactive Arthritis . In reactive arthritis, the joint is inflamed but not actually infected.

Chronic infectious arthritis

Chronic infectious arthritis begins gradually over several weeks. Very few cases of infectious arthritis are chronic. Chronic infectious arthritis most often affects people who have risk factors Chronic infectious arthritis Infectious arthritis is infection in the fluid and tissues of a joint usually caused by bacteria but occasionally by viruses or fungi. Bacteria, viruses, or fungi may spread through the bloodstream... read more .

The joints most commonly infected are the knee, shoulder, wrist, hip, elbow, and the joints of the fingers. Most bacterial, fungal, and mycobacterial infections affect only one joint or, occasionally, several joints. For example, the bacteria that cause Lyme disease most often infect knee joints. Gonococcal bacteria (gonococci), which cause gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, and throat or the membranes that cover... read more Gonorrhea , viruses (such as hepatitis), and occasionally some other bacteria can infect a few or many joints at the same time.

Causes of Infectious Arthritis

Acute infectious arthritis

Acute infectious arthritis is usually caused by bacteria and viruses.

Different bacteria can infect a joint, but the bacteria most likely to cause acute infectious arthritis depend on a person’s age:

There are many risk factors for infectious arthritis. Most children who develop infectious arthritis do not have identified risk factors.

Risk factors for acute infectious arthritis include

Chronic infectious arthritis

Risk factors for chronic infectious arthritis include

Did You Know...

  • People who have chronic arthritis, such as rheumatoid arthritis, and suddenly develop pain and swelling in a single joint should contact their doctor promptly, because they may have an infection even if they have no fever.

Symptoms of Infectious Arthritis

In acute infectious arthritis, symptoms usually begin over hours to a few days. The infected joint usually becomes severely painful and sometimes red and warm. Moving or touching it is very painful. Fluid collects in the infected joint, causing it to swell and stiffen. Symptoms sometimes also include fever and chills. Very rarely, septic shock Sepsis and Septic Shock Sepsis is a serious bodywide response to bacteremia or another infection plus malfunction or failure of an essential system in the body. Septic shock is life-threatening low blood pressure ... read more develops.

Gonococcal arthritis usually causes milder symptoms. People typically have a fever for 5 to 7 days. People may have skin blisters, bumps, sores, or rashes, or sores on the mouth or genitals and on the trunk, hands, or legs. Pain may move from one joint to another before a joint becomes swollen and tender. Tendons may become inflamed.

Infants and children too young to talk tend not to move the infected joint, are irritable, may refuse to eat, and may have a fever, or may have no fever. Young children with knee or hip infections may refuse to walk.

In chronic infectious arthritis, symptoms are usually gradual swelling, mild warmth, minimal or no redness of the joint area, and aching pain that may be mild and less severe than in acute infectious arthritis. Usually, a single joint is involved.

People may have other symptoms depending on the cause of infectious arthritis, such as symptoms of Lyme disease, or swollen lymph nodes if the cause is an infected bite wound.

Diagnosis of Infectious Arthritis

  • Analysis and culture of joint fluid

  • Blood tests

  • Sometimes sputum, spinal fluid, and urine tests

  • Sometimes x-rays, magnetic resonance imaging (MRI), or ultrasonography

Doctors typically suspect the diagnosis of infectious arthritis in people who have severe or unexplained arthritis and in people who have other combinations of symptoms that are known to occur in people who have infectious arthritis.

Usually, a sample of joint fluid is removed with a needle (called joint aspiration Joint aspiration (arthrocentesis) A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more Joint aspiration (arthrocentesis) , or arthrocentesis) as soon as possible. It is examined for an increased number of white blood cells and tested for bacteria and other organisms. The laboratory can usually grow and identify the infecting bacteria from the joint fluid (called a culture), unless the person has recently taken antibiotics. However, the bacteria that cause gonorrhea, Lyme disease, and syphilis are difficult to recover from joint fluid. If bacteria do grow in culture, the laboratory then tests which antibiotics would be effective.

A doctor usually does blood tests because bacteria causing joint infections often appear in the bloodstream. Sputum, spinal fluid, and urine may also be tested for bacteria to help determine the source of infection and determine whether the infection is anywhere else.

To make the bacteria easier to detect and identify, doctors may analyze the joint fluid using the polymerase chain reaction technique (a type of nucleic acid amplification test [NAAT]) to detect the DNA of gonococci and mycobacteria.

Prognosis for Infectious Arthritis

Infectious arthritis that is caused by nongonococcal bacteria can permanently destroy joint cartilage within hours or days.

Infectious arthritis that is caused by gonococcal bacteria does not usually damage joints permanently.

People with rheumatoid arthritis usually do not regain total use of the infected joint, and the risk of death is increased.

Treatment of Infectious Arthritis

  • Antibiotics or antifungal drugs

  • Removal of pus

  • Splinting of the joint, followed by physical therapy


It is important to start antibiotics as soon as an infection is suspected, even before the laboratory has identified the infecting organism. Antibiotics that kill the bacteria that are most likely causing the infection are given until the infecting organism is identified, usually within 48 hours of testing the joint fluid. Antibiotics are given by vein (intravenously) at first to ensure that enough of the drug reaches the infected joint.

If the antibiotics are effective against the infecting bacteria, some improvement usually occurs within 48 hours. As soon as the doctor receives the laboratory results, the antibiotic may be changed depending on the sensitivity of the particular bacteria to specific antibiotics. Intravenous antibiotics are continued for 2 to 4 weeks. Then, antibiotics are given by mouth at high doses for another 2 to 6 weeks.

An infection that lasts a long time and that does not go away after use of conventional antibiotics may be caused by mycobacteria or fungi. Infections caused by fungi are treated with antifungal drugs. Infections caused by mycobacteria are treated with a combination of antibiotics. Infections caused by fungi and mycobacteria require long-term treatment.

Infections caused by viruses usually get better without antibiotic treatment.

Removal of pus

The doctor often removes pus with a needle (aspiration) to prevent its accumulation because accumulated pus may damage a joint and may be more difficult to cure with antibiotics. If drainage with a needle is difficult (as with a hip joint) or unsuccessful, arthroscopy Arthroscopy A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more Arthroscopy (a procedure using a small scope to view the inside of the joint directly) or surgery may be needed to drain the joint. Aspiration is often done more than once. Sometimes a tube is left in place to drain the pus.

Splinting and physical therapy

Splinting of the joint (to keep it from moving) is done for the first few days of the infection to help ease pain, but physical therapy Physical Therapy (PT) Physical therapy, a component of rehabilitation, involves exercising and manipulating the body with an emphasis on the back, upper arms, and legs. It can improve joint and muscle function, helping... read more is then started to strengthen muscles and prevent stiffness and permanent loss of function.

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • Arthritis Foundation: Comprehensive information on various types of arthritis, including infectious arthritis, and information regarding living with arthritis

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