Early identification of patients that are at risk of developing foot complications is essential in preventing serious consequences such as chronic pain or even am putation. Foot pressure distribution is a well-established technique in the assessm ent of foot disorders especially in diabetic ulceration cases. However pressure m easurem ents alone do not provide enough information to evaluate a foot problem. It is believed that shear stress m easurem ents, along with pressure recordings, will increase our understanding of various mechanisms of foot disorders.

The purpose of this study was to investigate the pressure and shear stress profiles under the foot of subjects with a number of foot problems. The subject population consisted of adult and pediatric control subjects, diabetic neuropathic, rheumatoid arthritis and hallux valgus patients, and athletic individuals with a history of foot blisters. A custom-built pressure-shear platform consisting of 80 transducers was used to collect plantar stresses. Subjects were asked to walk barefoot over the measuring device which looks like a chessboard in appearance.

It was shown that there is neither a linear nor a non-linear relationship betw een plantar pressure and shear magnitudes, which suggests plantar shear should be measured rather than predicted. Locations of peak shear deviated from the locations of peak pressure by 2.3cm and 2.5cm under the fe et of control and diabetic subjects, respectively. This finding may explain the low correlation betw een the locations op peak pressure and ulceration. Diabetic and rheumatoid arthritis patients had increased shear magnitudes com pared with the control subjects. Shear-time integral values under the feet of athletic individuals were more than 40% higher with regard to both pediatric and adult control subjects. Plantar shear loading in hallux valgus subjects was observed to exhibit a lateral shift. As expected, propulsive shear forces under the hallux of these patients w ere reduced by 32%.

The results of this study will contribute to better understanding of foot interface stresses and their relationship with some of the major foot disorders which in turn may enable early diagnosis of these serious foot problems and yield to better management of complications.