Progress in the development of surgical implant materials has been hindered by the lack of basic information on the nature of the tissues, organs and systems being repaired or replaced. Materials' properties of living systems, whose study has been conducted largely under the rubric of tissue mechanics, has tended to be more descriptive than quantitative. In the early days of the modern surgical implant era, this deficiency was not critical. However, as implants continue to improve and both longer service life and higher reliability are sought, the inability to predict the behavior of implanted manufactured materials has revealed the relative lack of knowledge of the materials properties of the supporting or host system, either in health or disease. Such a situation is unacceptable in more conventional engineering practice: the success of new designs for aeronautical and marine applications depends exquisitely upon a detailed, disciplined and quantitative knowledge of service environments, including the properties of materials which will be encountered and interacted with. Thus the knowledge of the myriad physical properties of ocean ice makes possible the design and development of icebreakers without the need for trial and error. In contrast, the development period for a new surgical implant, incorporating new materials, may well exceed a decade and even then only short term performance predictions can be made.