Infectious arthritis is a painful infection in the 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 (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. Most often, the joint affected is a large joint such as the knee, hip, or shoulder. It occurs more often in children and older adults.
Certain people are more likely to have infectious arthritis than others. Risk factors include:
- joint problems such as arthritis, gout, and lupus
- previous joint surgery
- skin conditions and open wounds
- drug or alcohol abuse
- drugs that suppress the immune system
- weakened immune system
Symptoms of infectious arthritis can vary depending on the individual’s age, as well as the medications the individual is taking. Symptoms may include:
- severe pain that worsens with movement
- swelling of the joint
- warmth and redness around the joint
- decreased appetite
- rapid heartbeat
Your doctor will begin with an exam of the joint and by asking questions about your symptoms. If they suspect 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 how serious the infection is.
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 X-ray, MRI, CT scans, and nuclear scans.
Treatment for infectious arthritis 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 is effective for the type of bacteria present in your joint. To prevent osteoarthritis and damage to your joint, the infection needs to be treated promptly. As a result, your doctor may order antibiotics intravenously (IV), as this treats the infection more quickly than oral antibiotics. Most individuals 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 is important to take the entire course of antibiotics to treat the infection effectively.
If your infection is caused by a fungal infection, your doctor will prescribe antifungal medication instead of antibiotics.
Infectious arthritis caused by a virus does not require medication.
Synovial Fluid Drainage
Many individuals with infectious arthritis need to have their synovial fluid drained. This is done to remove the infected fluid, ease pain and swelling, and increase the speed of recovery. Synovial fluid is most often drained by arthroscopy. In this procedure, your doctor will make several small incisions near the affected joint. Then he or she will feed 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.
Sometimes doctors are able to use arthrocentesis, which uses a small needle, to remove infected fluid without requiring surgery. This procedure often has to be repeated over the course of several days to ensure enough fluid is drained.
Other Treatment Options
Rarely, more severe cases of infectious arthritis require surgery to wash out the joint, remove damaged sections of the joint, or replace the joint.
Other treatment methods to reduce pain may be used in conjunction with treatment of the infection. These methods include:
- using non-steroidal anti-inflammatory medications (NSAIDs)
- resting the joint
- applying heat to the joint
- splinting the affected joint
- physical therapy