I have osteoarthritis in both my knees, but recently developed septic arthritis in one of them. What is this?
Septic or infectious arthritis is an infection in the fluid and tissues of a joint. More commonly caused by bacteria, it may also be result from viruses or fungi.
Infection elsewhere in the body can travel through the bloodstream and infect a joint. Infection can also result from surgery, an injection or an injury to the joint.
Symptoms can develop over hours or days. The infected joint typically becomes red and warm. Moving or touching it can be very painful. Fluid collects in the infected joint, causing it to swell and stiffen. Fever and chills may also develop.
The joints most commonly infected are the knee, hip, shoulder, elbow, wrist and fingers. While usually only one joint is affected, occasionally several joints may be involved depending on the cause of the infection.
Those with other joint conditions – rheumatoid arthritis, osteoarthritis or arthritis from injury – are at increased risk of developing infectious arthritis.
Diagnosis is made by removing a sample of joint fluid with a needle. This fluid is examined for white blood cells, bacteria and other organisms.
Blood, sputum, spinal fluid and urine may also be tested for bacteria to help determine the source of infection.
At the hospital I was initially put on an intravenous antibiotic. After a day this was changed to a different type. Why was this?
Because an infected joint can be destroyed without prompt treatment, intravenous antibiotics are usually started as soon as an infection is suspected.
The antibiotic, however, may be changed depending on the sensitivity of the particular bacteria to specific antibiotics. If the antibiotics are effective against the infecting bacteria, improvement usually occurs within 48 hours.
Infections caused by fungi are treated with antifungal drugs while those caused by viruses usually get better without specific treatment.
Treatment may also include the removal of pus from the joint using a needle.
Where this is not possible, an arthroscopy – a procedure that uses a small scope to view the interior of the joint directly – or surgery may be needed to drain the joint.
Splinting of the joint may be helpful initially to help ease pain. Physiotherapy is also needed to prevent stiffness and permanent loss of function.
Non-steroidal anti-inflammatory drugs may be prescribed for temperature and pain control.
