Most people are familiar with osteoarthritis - the common "wear and tear" arthritis that occurs over years of musculoskeletal stress and injury, and the source of many of the aches and pains we attribute to aging. Another well-known ailment is rheumatoid arthritis, an autoimmune disease that usually affects several joints in the body at once. But there are actually about 100 types of arthritis and related disorders, many of which are caused by bacteria or viruses.
Arthritis is a condition in which the joints of the body become swollen, tender and inflamed. "With infectious arthritis, a bacterium, virus or other infection directly invades the joint and causes pus to form there," says James J. Nocton, MD, Associate Professor of Pediatrics at the Medical College of Wisconsin. "While infectious arthritis itself is not contagious, the cause of the infection can be." Dr. Nocton practices in the Division of Pediatric Rheumatology, Department of Pediatrics, at Children's Hospital of Wisconsin, a Medical College affiliate.
Bacteria such as staphylococcus aureus ("staph") and streptococcus ("strep") are the most common causes of infectious arthritis. These bacteria can gain access to the body in various ways, for example through a cut or break in the skin or via an ear infection. The infectious agent travels through the bloodstream and settles in a joint, where the body's own defense system - the immune response - fights against the intruder. The end result is inflammation.
Untreated Lyme disease, caused by a bacterium carried by the deer tick, can lead to infectious arthritis, as can untreated sexually transmitted diseases, particularly gonorrhea.
In addition to certain common bacteria, some viruses can also initiate arthritic disorders. Parvovirus, which causes the common childhood infection known as "fifth disease," can cause infectious arthritis in children or adults. While illness from parvovirus generally resolves without treatment, anti-inflammatory medications may be prescribed to treat joint swelling and pain if infectious arthritis develops.
People whose immune systems are already compromised by health conditions such as diabetes or sickle cell anemia may be at even greater-than-average risk of developing infectious arthritis.
Symptoms and Treatment
Infectious arthritis is usually quite painful. Children who are affected may even refuse to walk if their leg, ankle or foot joints are involved. In joints other than the hip or shoulder, swelling may be apparent, and the affected area might feel hot or look red. There is almost always a fever. (Infectious arthritis caused by Lyme disease, however, does not usually cause severe pain, fever or swelling.)
"With most cases of infectious arthritis, the patient feels sick," Dr. Nocton says. "The presence of a fever raises your suspicions that the cause of joint pain or swelling that does not resolve by itself may be infectious arthritis."
Health care providers typically diagnose bacterial arthritis by removing fluid from the affected joint through a needle, then culturing the fluid in the laboratory. The fluid will grow staph, strep or another infectious agent, thereby identifying the cause of the inflammation. X-rays or similar imaging tests may also be used, primarily to rule out other causes of inflammation.
Patients who are diagnosed with infectious arthritis of bacterial origin receive antibiotics - usually intravenously at first, followed by oral medications. Depending on the location of the joint and the severity of the inflammation, treatment might also include draining the joint of pus, particularly in the case of the hip, which is more sensitive to damage from inflammation. Infectious arthritis caused by Lyme disease does not usually require joint drainage, and only oral antibiotics are necessary for treatment.
Protection, Prevention
Since many cases of infectious arthritis begin with a skin injury, good wound care is essential to avoid future problems. In addition, there are ways to provide some degree protection from other sources of infection. Safe sex practices and anti-tick measures (e.g., using insect repellant and wearing long sleeves and pants when in the woods) can help prevent the infections that may lead to an arthritic condition.
If not treated promptly and properly, infectious arthritis can destroy cartilage, which lines bone surfaces in the joint, acts as a shock absorber and helps the joint move smoothly. Eventually, the cartilage could break down completely and the inflammation would cause the bone itself to deteriorate. Furthermore, the infection could spread to adjacent tissues or to other parts of the body through the bloodstream.
"The key is to diagnose the infection as soon as possible and start treatment," Dr. Nocton says. "This usually prevents the permanent damage to the joint."
