Septic arthritis: Clinical sciences

Septic arthritis refers to joint inflammation that occurs when a pathogen invades the joint space. Once within the synovial cavity, pathogens trigger the immune system and stimulate the production of cytokines that can eventually result in joint damage.

Now, there are various ways for bacteria to get into a joint. For example, it can spread directly from an infection in the adjacent bone, such as osteomyelitis. It can also reach the joint through hematogenous spread from a distant infectious site in the body; or by direct inoculation, which can occur as a complication of orthopedic surgery. Septic arthritis is usually monoarticular, affecting one large joint, and the diagnosis typically relies on synovial fluid aspiration and analysis.

Now, if you have a patient presenting with signs and symptoms of septic arthritis, you should first perform an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access, start IV fluids, and begin continuous vital sign monitoring including blood pressure, heart rate, and oxygen saturation. Provide supplemental oxygen, if needed, and don’t forget to start broad-spectrum IV antibiotics.

Okay, now let’s go back to the ABCDE assessment and look at stable patients. First, let’s start by taking a focused history and physical exam. Your patient will typically report monoarticular joint pain and swelling, commonly of the hips, knees, shoulders, or ankles. These joints are the most vulnerable to infection because they have a richer blood supply than small joints, and that enables pathogens to more easily reach the larger joints. Your patient might also report systemic symptoms, such as fever, malaise, and decreased appetite. They may also have a history of risk factors, including overlying skin infection or ulceration, history of a prosthetic joint or recent joint surgery, immunosuppression, IV drug use, and smoking.

Additionally, a physical exam may reveal an ill-appearing patient with a joint effusion, or erythema and warmth of the skin overlying the affected joint. Also, local edema and pain typically results in a limited range of motion of the affected joint.