The purpose of this investigation was to develop a new ultrasound technique capable of enhancing the present understanding of Total Knee (TKR) contact mechanics. Specifically, it was desired to measure contact areas as the primary path towards understanding fibio-femoral TKR articulation. Both ultrasound and Fujifilm methods were employed for comparison.

To this end, the present work was composed of four phases. In the first, a theoretical model was developed ultrasound behaviour at the interface of two mating bodies of known geometry. Two factors are especially influential in diagnostic ultrasound imaging, namely the ultrasound wavelength (i.e. Wavelength effect) and ultrasound beam width (i.e. Beam Thickness effect). Thus, the effect of these on the measurement of contact areas was modeled.

The second step involved the design and development of unique test targets and imaging protocols for determining ultrasound resolutions and important conversion factors. A comparison of two acoustic working media were studied, namely water and Ultra, High Molecular Weight Polyethylene (UBMWPE). It was found that the constants determined for these parameters were adequate in characterizing the ultrasound unit.

Third, another set of test objects and protocols was developed for experimental ultrasound validation of the theoretical two-body contact models. Specifically, several metal-0on-UHMWPE test interfaces of known geometry were constructed mimicking point and nonpoint contact. The existence of both the Wavelength and Beam Thickness effects was demonstrated experimentally, their behaviour being in good agreement with theory. The effect of load on Wavelength theory was also shown to be negligible.

The fourth phase involved the design and construction of an apparatus for testing a TKR at various load-angle configurations. Both ultrasound and Fujifilm methods were employed in measuring the contact areas at the tibio-femoral interface of the TKR. It was found that ultrasound and Fujifilm provided upper and lower-bound contact area solutions, respectively, based on their physical operating principles.

The larger implications of this study are threefold. (1) A New Technique for detecting 2D, in vitro, TKR contact areas was developed whose key feature is its non-intrusivity. However, the modality's potential in its present form is limited for in vivo clinical wear assessment, being potentially more useful as an industrial TKR design tool. (2) Upper and Lower-bounding of Contact Area solutions, using ultrasound and Fujifilm supports the idea that every technique indirectly measures the “gap” between mating parts because of limited resolution. Focus on bounding the contact arm solution using several methods rather than relying on one method should become characteristic of future studies. (3) The Contact Stress Criterion:​ Because of the precedent set in the literature in enlarging contact area (i.e. reducing contact strew) and, hence, diminishing fatigue-related wear, investigators have given relatively little attention to tangential stresses. The potential damage instigated by tangential tensile stresses at the outer edges of the contact area needs to be reconsidered in future TKR contact mechanics studies.