Computational assessment of combinations of gait modifications for knee osteoarthritis rehabilitation

Abstract

Gait modification is a noninvasive strategy for reducing the external knee adduction torque in patients with medial compartment knee osteoarthritis. Recently, a novel "medial thrust" gait pattern characterized by knee medialization during stance phase has been shown to reduce both adduction torque peaks significantly. While changes in footpath (i.e., toe out angle and stance width) also affect the adduction torque peaks, the extent to which footpath changes may alter the effectiveness of medial thrust gait is unknown. This study used a validated patient-specific computational model to investigate this issue. A dynamic optimization framework that accurately predicted adduction torque changes caused by knee medialization or footpath alteration for a specific patient was modified to predict the simultaneous effect of both factors. Medial thrust gait optimizations were then performed for the same patient using imposed footpath alterations consisting of all possible combinations of three toe out angles (nominal +/- 15 degrees) and three stance widths (nominal +/- 50 mm). Overall, predicted adduction torque reductions produced by medial thrust gait were relatively insensitive to footpath alterations. The 32%-34% reduction in both peaks achieved with the nominal footpath was augmented by at most 9% and reduced by at most 3% for the altered footpaths. When combined with knee medialization, footpath alterations would likely have only a secondary effect on knee adduction torque reductions for this particular patient.

Figure 1

Left knee adduction (a), hip abduction (b), knee extension (c), and ankle inversion (d) torque curves measured for the patient’s nominal gait motion (solid line) and predicted for the patient’s medial thrust gait motion using the nominal foot path (dashed line). Shaded regions indicate range of predicted torque curves for medial thrust gait with 9 foot path variations.