What is the medical term for fluid around a knee joint after injury?

• A. Edema
• B. Synovitis
• C. Hemarthrosis
• D. Effusion

Answer: (D)

Effusion is the accumulation of fluid within the joint capsule, so when the knee swells after an injury, the fluid inside the joint is called an effusion. Edema refers to general swelling in the surrounding tissues, not inside the joint space. Synovitis is inflammation of the joint's synovial lining, which can contribute to swelling but isn’t the term for the fluid itself. Hemarthrosis means blood in the joint, a specific type of effusion caused by bleeding. So the fluid around the knee after injury is best described as an effusion.