Characterisation of Knee Brace Migration and Associated Skin Deformation During Flexion by Full-Field Measurements

Fabric-based knee braces are widely used as orthotic devices to support and align the joint. Despite significant prescription, compliance with the treatment is often negatively affected by discomfort issues, in particular brace slippage and migration. Full-field measurements associated with digital image correlation were performed on 11 subjects to determine if the brace was able to follow skin deformation during knee flexion, which was suspected to be a primary slippage mechanism. This technique allowed measurement of relatively small slippage magnitudes, which proved to be mostly reversible on re-extension of the leg. Strain fields derived from these measurements indicated a strong influence of gender on skin deformations, and showed that slippage may be due to the inability of the brace fabric to match the non-linear mechanical behaviour of the skin. Consequently, compliance to knee braces may be improved by differentiating their design between genders and judiciously selecting fabrics based on their mechanical behaviour.