Septic arthritis, also known as reactive arthritis and bacterial arthritis, is inflammation of a joint caused by infection. When it develops, it represents a medical emergency. It develops when bacteria or fungus is transmitted through an individual’s bloodstream to a joint. Individuals can develop septic arthritis at any age but it is less common between the ages of three to adolescence.
The majority of acute cases involve bacteria such as staphylococcus or streptococcus. However, children who develop septic arthritis tend to be infected with Group B streptococcus or Haemophilus influenza, if they have not been vaccinated. The number of cases that progress to chronic infection is less common. Chronic infections are generally caused by organisms such as Mycobacterium tuberculosis and Candida albicans.
Overall, the most common sites of infection are the hip and knee joints. The following are considered risk factors for septic arthritis: artificial joint implants, bacterial infection, chronic disease (diabetes, rheumatoid arthritis, and sickle cell disease), intravenous drug use, immunosuppressive medications, and recent joint surgery or arthroscopy.
Septic arthritis generally presents with a rapid onset of symptoms. Patients develop a fever in addition to joint swelling, redness, and pain in the infected joint. Patients may also experience pseudoparalysis, which is an inability to move the extremity possessing the infected joint. To diagnose septic arthritis, physicians will aspirate the joint fluid to check the cell count, look for crystals under the microscope, and perform a gram stain and culture. In addition, other tests include a blood culture and an X-ray of the affected joint.
Possible complications include joint degeneration and permanent joint damage, which can occur if appropriate treatment is delayed. If antibiotics are promptly given to treat the infection the patient has a good prognosis. If fluid accumulates in the joint, aspiration may be necessary. Aspiration involves a needle being inserted into the joint to drain off the excess fluid. Only severe cases require surgery to remedy the infected joint fluid; however, if a prosthetic joint is affected, it may need to be replaced.