Osteoporosis (IMAGE) University of Texas at San Antonio Caption UTSA scientists believe that proteoglycans, which occur naturally in bones' extrafibrillar matrix in a small amount (less than 1.0% in volume), interact with water to sustain bones' ductility, or their ability to absorb energy and resist fracture. Credit Photo Courtesy of UTSA Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.