What type of injury involves the swelling and inflammation of a bursa?

Bursitis is the inflammation of the bursa, which are small, fluid-filled sacs that provide cushioning and reduce friction between tissues in the body, such as bone, muscle, tendons, and skin. When a bursa becomes irritated or injured, it swells and can cause pain in the affected area. This condition can result from repetitive movements, prolonged pressure, or direct trauma to the joint, leading to symptoms like swelling, tenderness, and restricted movement.

In contrast, tendinitis refers to the inflammation of a tendon, which connects muscle to bone, while a stress fracture is a hairline crack in a bone caused by overuse. IT Band Syndrome involves irritation of the iliotibial band, a ligament running along the outside of the thigh, but does not specifically relate to bursa inflammation. Thus, the characteristics and symptoms associated with bursitis clearly distinguish it as the correct answer.