The bone diagnostic instrument is designed to measure materials properties of bone even if it is covered with soft tissue such as periosteum, connective tissue and skin. It uses (1) a probe assembly, consisting of a reference probe that penetrates soft tissue and stops on the surface of the bone and a test probe that is inserted into the bone, (2) an actuation system that can move the test probe, typically into and out of the bone, (3) a sensing system that can determine the dynamics of the test probe as it moves in the bone, and (4) a measurement system to record the data that is sensed during the motion. In our current prototype, a sharpened, solid test probe slides inside a sharpened hypodermic syringe that serves as the reference probe. A load cell senses the force as a function of the distance that the test probe is inserted into the bone relative to the position of the reference probe that rests on the surface of the bone, measured with a linear variable displacement transformer. Examples of the type of data that can be taken with this prototype include cyclic force versus distance curves that show differences in material properties of different types of bone. (c) 2006 American Institute of Physics.