Septic Arthritis

Diagnosis

The following tests are commonly used to diagnose septic arthritis:

Joint fluid analysis
A sample of fluid is withdrawn from the affected joint using a needle. Changes in the fluid’s color, consistency, volume, and composition can indicate infection. Laboratory tests identify the specific organism causing the infection, guiding treatment.

Blood tests
Blood samples are taken to detect signs of infection in the bloodstream.

Imaging tests
X-rays and other imaging studies can assess joint damage or loosening of an artificial joint. In some cases, a specialized scan using a small amount of radioactive material may be done, especially if a prosthetic joint infection is suspected more than a year after surgery.

Treatment

Treatment for septic arthritis focuses on joint drainage and antibiotics.

Joint drainage
Removing infected joint fluid is critical. Methods include:

• Needle aspiration to withdraw fluid directly from the joint

• Arthroscopy, where a small camera and drainage tubes are inserted through tiny incisions

• Open surgery, often required for joints that are difficult to drain, such as the hip

Antibiotics
The specific antibiotic depends on the microorganism causing the infection. Treatment usually starts with intravenous antibiotics and may later switch to oral antibiotics. Therapy typically lasts two to six weeks and may have side effects like nausea, vomiting, diarrhea, or allergic reactions.

Removal of replacement joint
If an artificial joint is infected, treatment may involve removing the joint and temporarily placing an antibiotic cement spacer. A new replacement joint is implanted after several months. In some cases, the joint may be cleaned and damaged tissue removed while keeping the artificial joint in place, followed by prolonged antibiotic therapy to prevent recurrence.