- Septic arthritis (infectious arthritis) is a form of joint inflammation caused by a bacterial, viral or fungal infection.
- Common symptoms of septic arthritis include joint pain and swelling, and fever.
- Factors that increase the risk for contracting septic arthritis include conditions that weaken the immune system, and existing arthritis or other joint disease.
- Bacterial and fungal infections are usually treated with antibiotics and anti-fungal medication; viral infections generally resolve by themselves.
- If the infection is diagnosed and treated promptly, there is usually no lasting joint damage.
Septic arthritis (infectious arthritis) is a form of joint inflammation that results from a bacterial, viral or fungal infection. It represents a serious type of arthritis, as there is a potential for severe joint damage and in the case of bacterial arthritis, can result in severe and potentially life threatening sickness, requiring urgent treatment.
Who gets it and who is at risk?
- Anyone can get septic arthritis, although the following factors can put you at higher risk:
- Sickle-cell anaemia.
- Severe kidney disease.
- Some forms of cancer.
- Intravenous drug abuse.
- Infants and elderly people are generally more susceptible to infection.
- Existing arthritis or other joint disease: infectious agents tend to infect joints that are already damaged.
- Surgery to replace a damaged joint carries a small chance of septic arthritis. Infection mostly occurs within days to months after surgery, but can appear several years later.
- Certain drugs can decrease the body's ability to resist infection. Examples of such medications are azathioprine, methotrexate and cyclophosphamide, used to treat rheumatoid arthritis; and corticosteroids, such as prednisone. People who receive repeated injections of corticosteroids into the same joint have an increased risk of septic arthritis in that joint.
- Certain jobs can expose workers to disease-producing agents associated with septic arthritis. For example, people who work with animals, plants, soil or marine life, which can carry the infectious agents, may be predisposed to septic arthritis.
- Septic arthritis is not contagious (spread from one person to another). However, certain infections that may result in septic arthritis (e.g. German measles and gonorrhoea) are contagious.
Septic arthritis is caused by bacteria, viruses or fungi that enter the body through the skin, nose, throat, ears or through a wound. The infectious agents can travel in the bloodstream to settle in the joints.
Usually, one has already been sick from the infection elsewhere in your body before it reaches the joints. For example, if you develop septic arthritis from the pneumococcus bacterium, which causes pneumonia, you may already have experienced pneumonia in the lungs. After the initial infection, the bacteria can reach the joints and cause inflammation there.
Septic arthritis may also occur without a prior infection, but this is less common. Sometimes, an infectious agent may enter a joint directly through a nearby wound. Tissue around the joint can become infected after surgery, an injection or trauma (injury). Therefore any injection or procedure penetrating into the joint should be done in a sterile manner.
Post-infectious or reactive arthritis
Certain infectious agents may cause reactive (post-infectious) arthritis, in which the agent is no longer present, but arthritis develops weeks, months or even years later, as a reaction to the initial infection. The infection that precipitates the arthritis occurs at a site distant from the joint. Approximately three weeks later the arthritis activates, usually in the lower limb, especially in the ankle or knee. This is thought to occur because, in genetically susceptible people, the immune system "perceives" proteins normally present in the joint as similar to the prior infectious agent, triggering an autoimmune inflammatory reaction. Therefore you need genetic predisposition, and to “meet” the infective agent in the environment to precipitate the disease. The pathology thereafter is referred to an autoimmune reaction – i.e. immune against self.
Infections of the genital and gastrointestinal tract are the most common trigger sites of infection that lead to reactive arthritis. Common bacteria causing reactive arthritis include chlamydia, klebsiella, yersinia streptococcus and salmonella. However, in most cases the actual original bacterium or infectious agent is not identified and one obtains a history of an infective problem, such as diarrhoea or genital infection, with mouth ulcers and frequently a conjunctivitis occurring at the time or before the joints get inflamed. The triad of arthritis, conjunctivitis and urethritis (genital infection), used to be called Reiter syndrome.
Because these are not really associated with infection actively inside the joint, antibiotics are not necessarily the therapies of choice. The arthritis usually persists for two to six months before subsiding in the majority. However, in some people it continues and may even become severe requiring immunosuppressant therapy. In this situation, a referral to a rheumatologist or specialist is required to best treat the disease.
In those who have disease remission, potential for reactivation remains a possibility.
Bacteria and viruses cause most cases of septic arthritis.
Septic arthritis can arise from many viral diseases, including upper respiratory tract infections, HIV, hepatitis, German measles, parvovirus, mumps and infectious mononucleosis (glandular fever). In general, the arthritic symptoms disappear in a few days to one or two weeks, when the underlying disease has run its course. Some viruses, including Hepatitis B, Hepatitis C and HIV, may cause more chronic joint pain or inflammation. Several joints may be simultaneously affected.
Fungi are the least common cause of septic arthritis. Types of fungi that can result in arthritis are usually found in soil, bird droppings and certain plants (especially roses).
Symptoms and signs
Symptoms of septic arthritis often resemble those of several other medical conditions, and may include the following:
- Joint pain, stiffness and swelling.
- Usually only one joint is involved, though sometimes two or three joints become infected (depending on the infectious agent).
- Typically, the large joints (shoulders, hips, knees, elbow) are affected, but smaller joints (fingers, wrists, ankles) can also be involved. Smaller joints are more likely to become infected from a nearby wound. Among intravenous drug users, less commonly infected joints, such as those in the spine or breastbone, may be involved.
- Warmth and redness in surrounding tissue.
- Chills, fever, weakness.
- Skin rash.
Common symptoms of bacterial joint infection:
- Pain and swelling in only one joint, often the knee.
- Fever and shaking chills.
- Begins quite suddenly.
- Is usually severely swollen with heat and redness in the joint.
- The joint may have a lot of fluid in it – called an effusion.
- The pain is often extremely severe.
Common symptoms of viral joint infection:
- Aching all over the body.
- Mild fever or none.
- Usually resolves on its own.
- Many joints usually with milder generalised pain.
Common symptoms of tuberculosis or fungal joint infection:
- Pain and swelling may be in one area or throughout the body.
- Mild fever or none.
- Usually begins quite slowly, over weeks or months.
- Progressive disability.
- Weight loss and general ill health.
- Night sweats may occur.
To determine if you have septic arthritis, your doctor will ask about your symptoms and any other medical conditions, recent travel, illness or contact with people who have had infections. Work or home conditions might also provide diagnostic clues.
Your doctor will then likely perform a physical examination and order laboratory tests to find out if an infection is present, and its cause.
If the joint is swollen, and there is suspicion of infection, the joint should be aspirated with a needle – removing fluid for the laboratory.
Bacteria and fungi can usually be identified from the sample of joint fluid or tissue from the infected area. Blood and urine tests may also be helpful. If tuberculosis or fungi are suspected, a small sample of tissue (biopsy) may need to be taken from the joint and examined.
A viral infection is usually diagnosed by symptoms and medical history. After the infection has been present for weeks or longer, blood tests may show the body's virus-fighting proteins (antibodies), produced in response to a specific viral infection.
Prompt diagnosis of bacterial, tuberculous and fungal septic arthritis is necessary to prevent permanent damage to the joint. X-rays may be taken to determine if joint damage has occurred. More sophisticated scans may be required as early on, X-rays may be normal, and deep infection in bone and joints may be missed. Technetium bone scanning or magnetic scanning are quite useful to detect sites of deep infection.
Septic arthritis may require hospitalisation for diagnosis and treatment; the length of stay varies depending on the type of illness present. Sometimes, hospitalisation may be recommended in order to drain fluid from the infected joint, for surgery to the joint, or to allow for resting of the joint.
Treating bacterial infections
Septic arthritis caused by bacteria almost always requires immediate treatment with antibiotics, which can often improve symptoms within 48 hours. The antibiotic prescribed depends on the type of bacteria present, and can be taken orally or intravenously.
Often, antibiotics destroy an infection in days or weeks, but in some cases they must be continued over several months. In fact most infected joints require at least six weeks of antibiotics. Even though symptoms disappear, bacteria may still be present and can re-infect the area, so it is important to take all the antibiotics prescribed.
Treating viral infections
Viruses do not respond to antibiotics, and viral infections usually have to resolve on their own. Bed rest and drinking plenty of liquids helps with recovery. Viral infections do not usually cause joint damage.
Treating fungal infections
Septic arthritis caused by a fungus is the most resistant to treatment. Anti-fungal medications may be prescribed and often need to be taken for many months. Recurrence of the infection is always a possibility.
Frequently infected joints must be drained of excess fluid that has accumulated and can damage the joint. This is done by inserting a needle directly into the joint and withdrawing fluid. (Sometimes the joint is drained with a drainage tube, or by surgery.) The same joint may need to be drained several times if fluid build-up recurs. This procedure is generally simple and usually not very painful. In most cases, repeated drainage, together with appropriate doses of intravenous antibiotics, can prevent the need for surgery.
In some cases, the joint may need to be opened surgically so that damaged tissue can be removed. If serious damage has already occurred, surgical reconstruction of the joint may be considered. Surgery is also sometimes performed in the case of fungal infections to clean out the infected joint.
Resting and protecting the joints
Treatment may also include resting and protecting the joints, either at hospital or at home. While the joint is recovering from the infection, it may be necessary to immobilise the area with a splint. This helps reduce pain and tissue damage.
Once the infection has cleared up, your doctor will frequently recommend exercises to build up muscle strength and increase the joint's range of motion. A physical therapist can instruct you in how to do suitable exercises.
Unlike other types of arthritis, septic arthritis is usually not a long-term illness. Diagnosed promptly and treated properly, it generally has a good outcome. However, without proper treatment, the affected joints can become seriously damaged, and the infection can spread to other parts of the body. Most often, people with septic arthritis are able to resume their normal activities once the infection has been adequately treated.