Bursae are fluid-filled cavities located at tissue sites where tendons or muscles pass over bony prominences near joints. Their function is to facilitate movement and reduce friction between moving parts. When a bursa becomes infected, traumatized, or injured it is referred to as bursitis.Review Date:8/14/2011Reviewed By:Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.