Infectious Arthritis

Organisms that cause infection, mainly bacteria, usually spread to the joint from a nearby infection (such as osteomyelitis Osteomyelitis Osteomyelitis is a bone infection usually caused by bacteria, mycobacteria, or fungi. Bacteria, mycobacteria, or fungi can infect bones by spreading through the bloodstream or, more often, by... read more or an infected wound) or through the bloodstream. A joint can be infected directly if it is contaminated during surgery or by an injection or an injury (such as a bite wound from a person Human Bites Because human teeth are not particularly sharp, most human bites cause a bruise and only a shallow tear ( laceration), if any. Exceptions are on fleshy appendages, such as the ears, nose, and... read more or a bite from a dog, cat, or rat Animal Bites Most animal bites in the United States are from dogs and cats. Wounds should be cleaned and cared for as soon as possible. (See also Introduction to Bites and Stings.) Although any animal may... read more ).

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.

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 , 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.

If doctors suspect the infectious arthritis is caused by gonococci Gonorrhea Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae, which infect the lining of the urethra, cervix, rectum, or throat, or the membranes that cover... read more , samples are also taken from the urethra, cervix, rectum, and throat. Tests for chlamydial infection Chlamydia and Other Nongonococcal Infections Chlamydial infections include sexually transmitted infections of the urethra, cervix, and rectum that are caused by the bacteria Chlamydia trachomatis. These bacteria can also infect... read more of the genitals (another sexually transmitted infection) are also done because many people who have gonorrhea also have a chlamydial infection.

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.

Doctors may take x-rays X-rays 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 of the affected joint to rule out other conditions. Doctors may do magnetic resonance imaging Computed tomography (CT) and magnetic resonance imaging (MRI) 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 (MRI) if the joint cannot be easily examined or aspirated. MRI or ultrasonography Ultrasonography Ultrasonography is a type of medical imaging that uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. During an ultrasound, a device called a... read more is also done to identify accumulations of fluid or collections of pus (abscesses).

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.

Nonsteroidal anti-inflammatory drugs Nonsteroidal Anti-Inflammatory Drugs Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most pain... read more (NSAIDs) and sometimes other analgesics are used to help reduce pain, inflammation, and fever.

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