Infectious arthritis is an infection in a joint. It may also be referred to as septic arthritis. It occurs when an infection caused by a bacteria or virus spreads to a joint or the fluid surrounding the joint. This fluid is called the synovial fluid. This infection usually begins in another area of the body and spreads through the bloodstream to the joint tissue. The infection may also enter the body through surgery, open wounds, or injections.
Infectious arthritis usually only occurs in one joint. The condition typically affects a large joint such as the knee, hip, or shoulder. It occurs more often in children, older adults, and people who use illegal drugs.
The symptoms of infectious arthritis can vary depending on your age and the medications you're taking. The symptoms may include:
- severe pain that worsens with movement
- swelling of the joint
- warmth and redness around the joint
- a fever
- decreased appetite
- a rapid heart rate
Certain people are more likely to get infectious arthritis than others. The risk factors include:
- having joint problems such as arthritis, gout, or lupus
- having a history of joint surgery
- having certain skin conditions
- having open wounds
- abusing illegal drugs or alcohol
- taking drugs that suppress the immune system
- having a weakened immune system
- having cancer
- having diabetes
Your doctor will examine your joint and ask you questions about your symptoms. If they suspect you have infectious arthritis, they may order additional tests.
An arthrocentesis is a test frequently used to diagnose this condition. It involves inserting a needle into the affected joint to take a sample of synovial fluid. The sample is sent to the lab to be examined for color, consistency, and the presence of white blood cells and bacteria. The information from this test can tell your doctor if you have an infection in the joint and what is causing the infection.
Your doctor may also take a blood sample from you. This is another way to check your white blood cell count and to determine if any bacteria are present in your bloodstream. This information can help your doctor determine the severity of the infection.
Imaging tests may also be ordered to confirm the presence of infection. These tests can also help your doctor see if your joint has been damaged by the infection. Imaging tests used for infectious arthritis include:
- MRI scans
- CT scans
- nuclear scans
Treatment for infectious arthritis caused by a bacteria usually begins with antibiotics to kill the bacteria causing the infection. Your doctor will use the information from your tests to choose an antibiotic that's effective for the type of bacteria present in your joint. The infection needs to be treated promptly and aggressively to prevent osteoarthritis and damage to your joint. As a result, your doctor may order intravenous antibiotics, which are given through your veins. This treats the infection more quickly than oral antibiotics. Most people begin to feel better within 48 hours of their first antibiotic treatment.
Your doctor may also prescribe oral antibiotics to treat the infection. Oral antibiotics for infectious arthritis usually need to be taken for six to eight weeks. It's important to take the entire course of antibiotics to treat the infection effectively.
Your doctor will prescribe antifungal medication instead of antibiotics if a fungus is causing your infection.
Infectious arthritis caused by a virus doesn't require medication.
Synovial Fluid Drainage
Many people with infectious arthritis need to have their synovial fluid drained. This is done to remove the infected fluid, ease pain and swelling, and prevent further damage to the joint. Synovial fluid is often drained using arthroscopy, but it can be done in an open surgical procedure.
With arthroscopy, your doctor will make several small incisions near the affected joint. Then, they'll insert a small tube containing a camera into the incision. Your doctor will use the camera image to guide them in suctioning the infected fluid from your joint. Usually, a drain or tube will be inserted and left in the joint to keep the joint from swelling again. This drain is then removed in a few days.
Sometimes, a doctor can use a small needle to remove infected fluid without requiring surgery. This is called arthrocentesis. This procedure often has to be repeated over the course of several days to ensure the fluid has been removed.
Other Treatment Options
Most cases of infectious arthritis require surgery, such as arthroscopy or an open procedure, to wash out the joint. On occasion, surgery is required to remove any damaged sections of the joint or replace the joint, but this is only done after the infection has been treated.
Other treatment methods to reduce pain may be used along with treatment for the infection. These methods include:
- using nonsteroidal anti-inflammatory drugs
- resting the joint
- splinting the affected joint
- going to physical therapy