Septic arthritis is an infection in the joint (synovial) fluid and joint tissues. It occurs more often in children than in adults. The infection usually reaches the joints through the bloodstream. In some cases, joints may become infected due to an injection, surgery, or injury.

Different types of bacteria, viruses, and fungi can infect a joint. The types that can cause septic arthritis include:

• Staphylococcus aureus. These are common bacteria that often cause skin infections.
• Haemophilus influenzae. These are bacteria that can infect the larynx, trachea, and bronchi.
• Gram negative bacilli. This is a group of bacteria that includes E. coli.
• Streptococci. This is a group of bacteria that can lead to a wide variety of diseases.
• Gonococci. This is the bacterium that causes gonorrhea.
• Viruses. Viruses, such as HIV, can infect the joints of people of all ages.

The most common type of bacteria that causes septic arthritis is Staphylococcus aureus. It's also known as S. aureus. The bacteria can enter the body in a number of ways, such as:

• A broken bone that goes through the skin (open fracture).
• An infection that spreads from another place on the body, such as the skin or genitals.
• An infected wound.
• A foreign object that goes through the skin.
• An injury that breaks the skin.

Risk factors for septic arthritis include:

• A systemic blood-borne infection.
• I.V. (intravenous) drug use.
• Osteoarthritis.
• A past history of septic arthritis.
• Rheumatoid arthritis.

Other factors that may increase the risk for septic arthritis include:

• Alcoholism.
• Diabetes.
• HIV.
• Lung or liver disorders.
• An older age.
• A suppressed immune system.

The most common joints affected by septic arthritis are the knee, hip, shoulder, elbow, wrist, and finger. Most often, only one joint is affected. Symptoms can occur a bit differently in each person, but common symptoms include:

• Fever.
• Joint pain.
• Joint swelling.

The symptoms of septic arthritis can look like other health conditions. Make sure you see your doctor for a diagnosis.

Early diagnosis of septic arthritis is important. This is to prevent lasting joint damage. The process starts with a medical history and a physical exam. Tests may also be done, such as:

• Removal of joint fluid. This is done to check the fluid for white blood cells and bacteria.
• Blood tests. These are done to look for bacteria.
• Phlegm, spinal fluid, and urine tests. These are done to look for bacteria and find the source of infection.

Treatment will depend on your symptoms, age, and general health. It will also depend on what type of germ is causing the infection and how severe the condition is.

Bacterial septic arthritis often needs treatment right away with antibiotics. This can improve symptoms within 48 hours. Some infections caused by fungi need treatment with anti-fungal medicine. Viral infections are not treated with medicine.

Fluid (pus) may be drained from the joint. A buildup of pus can damage the joint. The pus is drained with a needle, tube, or surgery. It's possible that pus may need to be drained multiple times from the joint over the course of treatment. Other treatment may include:

• Medicines for pain and fever.
• Physical therapy and gentle exercise to keep muscle strength.
• A splint on the joint to relieve pain.

Septic arthritis can destroy the joint cartilage. This can cause lasting damage to the joint.

If your symptoms get worse or you have new symptoms, let your doctor know.

• Septic arthritis is an infection in the joint (synovial) fluid and joint tissues.
• Different types of bacteria, viruses, and fungi can infect a joint.
• Symptoms include fever, joint pain, swelling, redness, and warmth.
• Quick treatment with antibiotics for bacterial septic arthritis is needed to halt the risk of joint damage.
• Other treatments include medicines for pain and fever, drainage of the joint, physical therapy, and a splint.
• Septic arthritis is a serious condition that can cause significant illness or even lead to death if not treated properly.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new directions your doctor gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions.