The limitations of the instantaneous centre of rotation in joint research.

The limitations on the use of the instantaneous centre of rotation (ICR), as calculated from discrete displacement data, are often not fully appreciated. As a consequence, the concept of the ICR has been improperly applied in some instances. In this paper, the procedures used to compute the ICR are developed in detail, and the factors that affect the computed results are identified. With an example, it is shown that in addition to being path dependent, ICR location is also sampling increment size dependent. Therefore, it is not appropriate to consider the ICR as a rotation centre if the body is undergoing general planar (combined translation and rotation) motion because it does not uniquely characterize the movement.