REFRAME

Introduction

Kinematic analysis involves calculating signals from optical or inertial datapoints to represent the relative movement of joint segments. The exact choice of local segment frame orientation and position in a bone segment has been shown to drastically influence the shape and magnitude of the associated kinematic signals, making the consistent interpretation of the underlying joint motion a challenge. Despite ISB recommendations aiming to standardise the reporting of these signals, a lack of consensus around joint coordinate frame definitions remains. An approach capable of accommodating different analytical methods and ultimately reconciling these differences in frame alignment, while ensuring consistent interpretations, is therefore crucial.
Here, we present REFRAME (REference FRame Alignment MEthod), an approach to minimise cross-talk between axes of a movement, and thereby provide kinematic patterns that can be reliably compared without requiring direct knowledge of the relative poses of the different segment frames. In this manner, REFRAME can enable the consistent interpretation and comparison of joint kinematics derived using different approaches.