Giant pes anserinus bursitis: A rare soft tissue mass of the medial knee

Bursae are small, jelly-like sacs that are located throughout the body, mainly around the shoulder, elbow, hip, knee, and heel in a number over 150. They contain a small amount of fluid, and are positioned between bones and soft tissues, acting as cushions to help reduce friction. Pes anserinus bursae, despite being clinically frequent, are not visible either by ultrasound (US) or magnetic resonance image (MRI). In some cases, we may observe a small fluid collection. The present case-report demonstrates the full clinical picture of a giant pes anserinus bursae beginning from clinical observation to its final pathology exam.