Translational medicine must increasingly turn its attention to the aging population and the musculoskeletal deterioration that it entails. The latter involves the integrated function of both muscle and bone. Musculoskeletal science has an established interest in such problems in relationship to osteoporosis of bone. The introductory concepts in this paper consider the extent to which loss of muscle mass and function, or sarcopenia, will be the next major translational target. Its epidemiology shows parallels with that of osteoporosis, and the two tissues have a close functional relationship. Its etiology likely involves a loss of motor units combined with cellular signaling and endocrine changes. Finally, the possibility of modification of these physiological changes in the context of management of the sarcopenic condition is considered.