1School of Mechanical Engineering, Purdue University Lafayette, Indiana, U.S.A.
All joints of human and animal bodies permit six degrees of freedom to varying extents. Thus to accurately measure the motion permitted by any anatomical joint, all six degrees of freedom must be taken into account. The objective of Part I of this paper is to present the analytical basis for a measurement system which incorporates an instrumented spatial linkage capable of doing this.
The system permits both the study of the overall relative motion between two adjacent body segments (e.g. bones) as well as the detailed study of the relative motion between the two complementary articular surfaces of the intervening joint. The mathematical development is carried out in matrix algebra to facilitate data reduction using the digital computer.