The overall goal of this thesis is to evaluate a novel variable-stiffness sole intervention shoe in its ability to reduce the adduction moment at the knee and to improve pain and functionality in patients with medial compartment knee osteoarthritis. The adduction moment at the knee has been shown to be related to the progression of medial compartment knee osteoarthritis. Thus, if the footwear intervention is able to reduce the adduction moment at the knee, it has the potential to slow the progression of this debilitating disease, and to improve clinical symptoms including pain and functionality in patients. This thesis provides the results of a comprehensive one-year randomized controlled study of the variable-stiffness intervention shoe.

Immediate effects of the intervention shoes showed a reduced peak knee adduction moment compared to a constant-stiffness sole control shoe at self-selected slow, normal, and fast walking speeds, with reductions increasing with increased walking speed. Secondary changes in frontal plane moments showed primarily reductions in other lower extremity joints, suggesting that the intervention shoes reduce the adduction moment at the knee without adversely affecting other joints. Analysis of the adduction moment after six months of shoe wear revealed that the variable-stiffness shoe continued to provide reduction in the peak knee adduction moment. Additionally, the WOMAC score, a disease-specific survey of pain and difficulty with functionality in osteoarthritic patients, was significantly reduced from the baseline test. The reductions in the adduction moment and improvements in pain and functionality were not seen in the patients randomly and blindly assigned to the constant-stiffness control shoes over the 6 month period. Furthermore, the intervention group had a significantly greater proportion of patients achieving a clinically important improvement in pain, defined as a 30% reduction in the pain score of the WOMAC survey, than the control group. Results after 12 months of shoe wear indicated that disease severity influences patient response to the intervention, with greater efficacy in reducing the knee adduction moment and in reducing pain and improving functionality for the less severe intervention group. Restriction of ankle motion by application of a semi-rigid ankle brace in conjunction with the intervention shoe in healthy subjects showed greater reductions in the knee adduction moment, suggesting that ankle motion restriction may enhance the effects of the intervention shoe. Finally, in order to implement such an intervention in a clinical or retail setting without the need for a gait laboratory, we demonstrated in healthy individuals that increases or decreases in the knee adduction moment with a footwear intervention can be predicted from changes in pressure distribution at the foot.

There is a clear need for non-invasive treatments for osteoarthritis that have the ability to slow the progression of the disease. Taken together, the results of mis project indicate that a variable-stiffness sole intervention shoe has the potential to serve as an inexpensive, non-invasive treatment for medial compartment knee osteoarthritis, and to improve the quality of life for many individuals afflicted with this disease.