Effect of walking in footwear with varying heel sole differentials on shank and foot segment kinematics.

Background: When walking in footwear with a positive "heel sole differential", the sagittal kinematics of the base of the footwear appear to mimic normal barefoot foot kinematics, creating an "effective foot," yet sagittal shank, thigh, and trunk kinematics appear to remain unchanged. These observations have not been quantified.

Objectives: To quantify these observations by assessing the effect of different heel sole differentials on sagittal shank and foot segment kinematics of able-bodied walking.

Study Design: Cross-sectional study.

Methods: Gait data from 10 nondisabled females were collected while they walked with no-heel (mean heel sole differential = 0 (standard deviation = 0) mm), mid-heel (mean heel sole differential = 37 (standard deviation = 10) mm), and high-heel shoes (mean heel sole differential = 71 (standard deviation = 17) mm) to calculate the shank-to-vertical angle and foot-to-horizontal angle.

Results: There were no significant differences between shoe conditions in stride lengths ( p = 0.056) or shank kinematics between 0% and 50% gait cycle ( p = 0.079). There were significant differences in foot kinematics ( p = 0.000), with foot segment angle increasing with increasing heel sole differential.

Conclusion: The ankle joint and actual foot segment adapt their kinematics to maintain consistent shank kinematics. The finding that heel sole differential and foot segment angle can be varied without influencing shank segment kinematics has implications for orthotic and prosthetic practice. Clinical relevance Heel sole differentials of footwear can be varied without implications for shank kinematics, which is relevant for both orthotics and prosthetics. Assessments and interventions with varying heel sole differential footwear may be helpful in patients with short calf muscle or restricted ankle motion who may walk more normally if an appropriate heel sole differential were provided.