Motor vehicle and work-related accidents, competitive athletics, and vigorous recreational activities frequently cause strains, sprains, contusions, lacerations, and ruptures of the musculoskeletal soft tissues. These injuries can lead to significant pain and disability and may be more difficult to treat than fractures. Despite the importance of these injuries, clinical studies and scientific investigations of musculoskeletal soft-tissue injuries have lagged behind similar work on bone fracture and repair. The lack of sufficient clinical and scientific information has limited progress in understanding of specific soft-tissue injury and repair responses and the development of new methods to accelerate repair and improve the quality of the repair tissue.