A prosthesis for reducing injury to soft tissues of the body, comprising an implantable member adapted to simulate at least one of a size or a shape of a naturally occurring bursa, where the member may be inflatable or otherwise expandable, flexible or rigid, and may be composed of a biocompatible, biodegradable, or non-biodegradable material. The member is adapted to be implanted at a musculoskeletal attachment site or at a site between a muscle and a bone, and is shaped and sized to reduce injury to the site. The prosthesis may also include a plug which seals the prosthesis automatically upon removal of an inflation tube.