Infectious arthritis (in-FEK-shus ar-THRY-tis) is a bacterial, fungal, or viral infection of the tissue and fluid within a joint*. The infection causes inflammation and can result in pain, swelling, and limited motion of the joint.
- is the structure where two or more bones come together, allowing flexibility and motion of the skeleton.
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Most of the time, bacteria cause infectious arthritis. This form of arthritis is also called septic arthritis, and the infected joint is referred to as a “septic joint.” Staphylococcus (stah-fih-lo-KAH-kus) or Streptococcus (strep-tuh-KAH-kus) bacteria are the culprits in most cases of septic arthritis. Arthritis also can occur in Lyme disease, tuberculosis, and many other infections. Bacteria can be introduced directly into the joint by injury or surgery, but more often the bacteria are carried to the joint through the bloodstream from an infection somewhere else in the body. The most common cause of septic arthritis in young adults is Neisseria gonorrhoeae (nye-SEER-e-uh gah-no-REE-eye), the bacterium that causes gonorrhea. These bacteria may spread from infected areas, such as the cervix* and rectum*, and infect joints at the hands, wrists, elbows, and knees. Certain viruses, including those that produce measles, rubella (roo-BEH-luh, a rash-causing viral infection that is also called German measles), and hepatitis B or C, also can cause arthritis. Fungi found in soil, bird droppings, and some plants are uncommon causes of infectious arthritis.
- (SIR-viks) is the lower, narrow end of the uterus that opens into the vagina.
People whose immune systems are weak because they have a disease such as diabetes*, sickle-cell disease*, certain cancers, lupus*, or AIDS are more likely to get infectious arthritis. Alcoholism and intravenous drug use also put people at higher risk. Because a joint that is damaged is more vulnerable to germs, people with existing disease involving the joints (for example, rheumatoid arthritis*) are more likely to develop infectious arthritis. Anyone who has had joint-replacement surgery is at increased risk for infection of that joint in the future.
- (dye-uh-BEE-teez) is a condition in which the body’s pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.
- *sickle-cell disease
- is a hereditary condition in which the red blood cells, which are usually round, take on an abnormal crescent shape and have a decreased ability to carry oxygen throughout the body.
- (LOO-pus) is a chronic, or long-lasting, disease that causes inflammation of connective tissue, the material that holds together the various structures of the body.
- *rheumatoid arthritis
- (ROO-mahtoyd ar-THRY-tis) is a chronic disease characterized by painful swelling, stiffness, and deformity of the joints.
Some places in the world have more cases of infectious arthritis than others. Rates are highest in Africa, Latin America, and Asia. In the United States, about 20,000 cases of infectious arthritis occur each year. Men, women, and children of all ages can get infectious arthritis, but almost half of patients in whom the illness is diagnosed are 65 years or older.
Infectious arthritis is not contagious, but certain viruses and the bacterium that causes gonorrhea can be transmitted from one person to another. This does not necessarily mean that someone who gets a particular infection caused by these organisms will also get infectious arthritis.
The symptoms of infectious arthritis vary by type of infection and the particular joint that is affected. With septic arthritis, symptoms usually appear within a few hours or days and include redness, warmth, swelling, pain, and sometimes fever and chills. It is difficult to move the affected joint because of the pain and swelling. Arthritis from a viral infection tends to come on more slowly, often with absence of fever and with less swelling, limitation of movement, and pain at the affected joint. Viruses may infect the joint directly, or sometimes the response of the body’s immune system to a virus may cause joint inflammation (called “postinfectious arthritis”). Inflammation stemming from a fungal infection or tuberculosis usually develops very slowly, sometimes over weeks or months. The bacteria that cause Lyme disease can settle in a joint and may lead to recurrent bouts of arthritis. Usually, swelling and limitation of movement of the joint are the main symptoms of this form of arthritis.
A doctor who suspects infectious arthritis based on a patient’s symptoms and the findings of a physical examination will want to know the details of the person’s medical history. Taking a medical history might include asking questions about whether the patient is sexually active, injects drugs, has been bitten by a tick (which can cause Lyme disease), has had arthritis in the past, or has recently been injured, hospitalized, or exposed to an illness. Laboratory tests can help confirm the diagnosis. A common diagnostic test is aspiration* of some of the synovial fluid* within the affected joint. The doctor inserts a thin, sterile needle through the skin directly into the joint and removes a sample of fluid. The fluid is then examined under a microscope to look for evidence of microorganisms (such as bacteria) and infection-fighting white blood cells. Some of the sample is put in a jelly-like medium containing nutrients that support the growth of bacteria, and this is placed in an incubator for a few days. If bacteria grow, bacterial infectious arthritis is diagnosed. This synovial fluid also can be tested for evidence of viral or fungal infections. In addition, blood tests can help diagnose arthritis caused by a virus or bacterium. If the suspected cause of inflammation is a fungus or tuberculosis, a tissue sample from the infected joint may need to be removed and analyzed. X rays, computerized tomography*, or magnetic resonance imaging* studies can detect excess fluid and sometimes destruction of the tissues within or surrounding an affected joint.
- (as-puh-RAY-shun) is the sucking of fluid or other material out of the body, such as the removal of a sample of joint fluid through a needle inserted into the joint.
- (sih-NO-vee-ul) fluid is the fluid produced in the synovium, the inner lining of the flexible capsule that encloses the joint space between two bones. This fluid lubricates and nourishes the joint.
- *computerized tomography
- (kom-PYOO-ter-ized toe-MAH-gruh-fee) or CT, also called computerized axial tomography (CAT), is a technique in which a machine takes many X rays of the body to create a three-dimensional picture.
- *magnetic resonance imaging (MRI)
- uses magnetic waves, instead of X rays, to scan the body and produce detailed pictures of the body’s structures.
The type of organism causing arthritis determines which medicines are needed to treat the infection. Antibiotics are prescribed to treat joint in- fections caused by bacteria, and anti-fungal medications are given for infection due to a fungus. Doctors also may recommend that a person with infectious arthritis keep the affected joint elevated, or raised up, and avoid moving it. Over-the-counter anti-inflammatory medications, such as ibuprofen, can relieve swelling and pain. Sometimes, to help healing and decrease discomfort, some of the excess synovial fluid is removed from a joint. This procedure may have to be repeated several times. In certain cases, a septic joint might be drained by a surgical procedure to help cure the infection.
Eliminating the infection can take time. Antibiotics may need to be given intravenously for 3 weeks or more. It may take even longer for someone to be able to use an affected joint without pain. In cases of severe infectious arthritis, physical therapy may be recommended after other treatment has been completed, to help patients recover full movement and function of the joint. Infectious arthritis can be cured with prompt and proper treatment. In cases that are severe or where treatment is delayed, the infection may cause permanent damage to the joint and the bone, sometimes resulting in persistent pain and disability.
Abstinence (not having sex) will prevent arthritis caused by STDs like gonorrhea. For sexually active people, the use of latex condoms can lessen the risk of exposure to bacteria that can cause arthritis. Doctors may recommend that people who have a high risk of the disease, such as those with artificial joints, take antibiotics to prevent an infection in the joint, even when the person has no symptoms of disease.
Rubella (German Measles)
Sexually Transmitted Diseases
The Arthritis Society, 393 University Avenue, Suite 1700, Toronto, Ontario, Canada M5G 1E6. The Arthritis Society details types of arthritis on its website and tracks research on causes and treatment of the disease.
Telephone 416-979-7228 http://www.arthritis.ca
U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894. The National Library of Medicine has a website packed with information on diseases and drugs, consumer resources, dictionaries and encyclopedias of medical terms, and directories of doctors and helpful organizations.
Telephone 888-346-3656 http://www.nlm.nih.gov
Infectious arthritis, which is sometimes called septic arthritis or pyogenic arthritis, is a serious infection of the joints characterized by pain, fever, occasional chills, inflammation and swelling in one or more joints, and loss of function in the affected joints. It is considered a medical emergency.
Infectious arthritis can occur in any age group, including newborns and children. In adults, it usually affects the wrists or one of the patient's weight-bearing joints-most often the knee-although about 20% of adult patients have symptoms in more than one joint. Multiple joint infection is common in children and typically involves the shoulders, knees, and hips.
Some groups of patients are at greater risk for developing infectious arthritis. These high-risk groups include:
- Patients with chronic rheumatoid arthritis.
- Patients with certain systemic infections, including gonorrhea and HIV infection. Women and male homosexuals are at greater risk for gonorrheal arthritis than are male heterosexuals.
- Patients with certain types of cancer.
- IV drug abusers and alcoholics.
- Patients with artificial (prosthetic) joints.
- Patients with diabetes, sickle cell anemia, or systemic lupus erythematosus (SLE).
- Patients with recent joint injuries or surgery, or patients receiving medications injected directly into a joint.
Causes and symptoms
In general, infectious arthritis is caused by the spread of a bacterial, viral, or fungal infection through the bloodstream to the joint. The disease agents may enter the joint directly from the outside as a result of an injury or a surgical procedure, or they may be carried to the joint by the blood from infections elsewhere in the body. The specific organisms vary somewhat according to age group. Newborns are most likely to acquire gonococcal infections of the joints from a mother with gonorrhea. Children may also acquire infectious arthritis from a hospital environment, often as a result of catheter placement. The organisms involved are usually either Haemophilus influenzae (in children under two years of age) or Staphylococcus aureus. In older children or adults, the infectious organisms include Streptococcus pyogenes and Streptococcus viridans as well as Staphylococcus aureus. Staphylococcus epidermidis is usually involved in joint infections related to surgery. Sexually active teenagers and adults frequently develop infectious arthritis from Neisseria gonorrhoeae infections. Older adults are often vulnerable to joint infections caused by gram-negative bacilli, including Salmonella and Pseudomonas.
Infectious arthritis often has a sudden onset, but symptoms sometimes develop over a period of three to 14 days. The symptoms include swelling in the infected joint and pain when the joint is moved. Infectious arthritis in the hip may be experienced as pain in the groin area that becomes much worse if the patient tries to walk. In 90% of cases, there is some leakage of tissue fluid into the affected joint. The joint is sore to the touch; it may or may not be warm to the touch, depending on how deep the infection lies within the joint. In most cases the patient will have fever and chills, although the fever may be only low-grade. Children sometimes develop nausea and vomiting.
Septic arthritis is considered a medical emergency because of the damage it causes to bone as well as cartilage, and its potential for creating septic shock, which is a potentially fatal condition. Staphylococcus aureus is capable of destroying cartilage in one or two days. Destruction of cartilage and bone in turn leads to dislocations of the joints and bones. If the infection is caused by bacteria, it can spread to the blood and surrounding tissues, causing abscesses or even blood poisoning. The most common complication of infectious arthritis is osteoarthritis.
The diagnosis of infectious arthritis depends on a combination of laboratory testing with careful history-taking and physical examination of the affected joint. It is important to keep in mind that infectious arthritis can coexist with other forms of arthritis, gout, rheumatic fever, Lyme disease, or other disorders that can cause a combination of joint pain and fever. In some cases, the doctor may consult a specialist in orthopedics or rheumatology to avoid misdiagnosis.
The patient's history will tell the doctor whether he or she belongs to a high-risk group for infectious arthritis. Sudden onset of joint pain is also important information.
The doctor will examine the affected joint for swelling, soreness, warmth, and other signs of infection. Location is sometimes a clue to diagnosis; infection of an unusual joint, such as the joints between the breastbone and collarbone, or the pelvic joints, often occurs in drug abusers.
Laboratory testing is necessary to confirm the diagnosis of infectious arthritis. The doctor will perform an arthrocentesis, which is a procedure that involves withdrawing a sample of synovial fluid (SF) from the joint with a needle and syringe. SF is a lubricating fluid secreted by tissues surrounding the joints. Patients should be warned that arthrocentesis is a painful procedure. The fluid sample is sent for culture in the sealed syringe. SF from infected joints is usually streaked with pus or looks cloudy and watery. Cell counts usually indicate a high level of white cells; a level higher than 100,000 cells/mm3 or a neutrophil proportion greater than 90% suggests septic arthritis. A Gram's stain of the culture obtained from the SF is usually positive for the specific disease organism.
Doctors sometimes order a biopsy of the synovial tissue near the joint if the fluid sample is negative. Cultures of other body fluids, such as urine, blood, or cervical mucus, may be taken in addition to the SF culture.
Diagnostic imaging is not helpful in the early stages of infectious arthritis. Destruction of bone or cartilage does not appear on x rays until 10-14 days after the onset of symptoms. Imaging studies are sometimes useful if the infection is in a deep-seated joint.
Infectious arthritis requires usually requires several days of treatment in a hospital, with follow-up medication and physical therapy lasting several weeks or months.
Because of the possibility of serious damage to the joint or other complications if treatment is delayed, the patient will be started on intravenous antibiotics before the specific organism is identified. After the disease organism has been identified, the doctor may give the patient a drug that targets the specific bacterium or virus. Nonsteroidal anti-inflammatory drugs are usually given for viral infections.
Intravenous antibiotics are given for about two weeks, or until the inflammation has disappeared. The patient may then be given a two- to four-week course of oral antibiotics.
In some cases, surgery is necessary to drain fluid from the infected joint. Patients who need surgical drainage include those who have not responded to antibiotic treatment, those with infections of the hip or other joints that are difficult to reach with arthrocentesis, and those with joint infections related to gun-shot or other penetrating wounds.
Patients with severe damage to bone or cartilage may need reconstructive surgery, but it cannot be performed until the infection is completely gone.
Monitoring and supportive treatment
Infectious arthritis requires careful monitoring while the patient is in the hospital. The doctor will drain the joint on a daily basis and remove a small sample of fluid for culture to check the patient's response to the antibiotic.
Infectious arthritis often causes intense pain. Patients are given medications to relieve pain, together with hot compresses or ice packs on the affected joint. In some cases the patient's arm or leg is put in a splint to protect the sore joint from accidental movement. Recovery can be speeded up, however, if the patient practices range-of-motion exercises to the extent that the pain allows.
The prognosis depends on prompt treatment with antibiotics and drainage of the infected joint. About 70% of patients will recover without permanent joint damage. However, many patients will develop osteoarthritis or deformed joints. Children with infected hip joints sometimes suffer damage to the growth plate. If treatment is delayed, infectious arthritis has a mortality rate between 5% and 30% due to septic shock and respiratory failure.
Some cases of infectious arthritis are preventable by lifestyle choices. These include avoidance of self-injected drugs; sexual abstinence or monogamous relationships; and prompt testing and treatment for suspected cases of gonorrhea. Patients receiving corticosteroid injections into the joints for osteoarthritis may want to weigh this treatment method against the increased risk of infectious arthritis.
Hellman, David B., "Arthritis & Musculoskeletal Disorders." In Current Medical Diagnosis and Treatment, 1998, edited by Stephen McPhee, et al., 37th ed. Stamford: Appleton & Lange, 1997.
Arthrocentesis— A procedure in which the doctor inserts a needle into the patient's joint to withdraw fluid for diagnostic testing or to drain infected fluid from the joint.
Pyogenic arthritis— Another name for infectious arthritis. Pyogenic means that pus is formed during the disease process.
Sepsis— Invasion of the body by disease organisms or their toxins. Generalized sepsis can lead to shock and eventual death.
Septic arthritis— Another name for infectious arthritis.
Synovial fluid (SF)— A fluid secreted by tissues surrounding the joints that lubricates the joints.