Development and validation of a software tool for knee joint biomechanics: extraction and processing of in vitro experimental motion capture data

Kinematics is the description in terms of relative motion between two rigid bodies. The knee joint is the largest in the human body and certainly one of the most complex, both from an anatomical and functional point of view, and thus its kinematics have involved researchers for a long time. In 1983, Grood and Suntay presented a joint coordinate system for the description of the three-dimensional rotational and translational motion between two rigid bodies, and they applied this system to the knee joint. A fundamental role in the kinematic analysis of the joints is played by motion capture systems; in fact, using certain experimental setups are obtained the coordinates of the markers which will be used to calculate, in the case of the knee, joint rotations and clinical translations. One of the major problems is to use the correct data acquisition protocol and above all to have the software tools to post-process the data and obtain joint kinematics also to carry out comparative and statistical analyzes. This thesis, therefore, describes an experimental protocol for in vitro kinematic analyzes of the knee joint, proposing a new experimental marker set and the development of the Kinematic Analysis Software (KKS), conceived as an application for the knee joint and implemented with MATLAB®. In particular, the software calculates clinical angles and translations elaborating the coordinates of markers positioned on specific landmarks of femur and tibia, compute measurements of mean and standard deviation of multiple tests and allows to perform a statistical analysis between two datasets, based on the Student’s t-test. The software has undergone a first phase of validation using an anatomical plastic model of the knee and is intended for further future tests to ensure its reliability.