An Investigation of Heel Rise Test, Postural and Tibial Sway During Single-Leg Stance in Pes Planus: A Pilot Study

Background: Pes planus (PP) is a common orthopedic condition in adults, characterized by a reduction in medial longitudinal arch (MLA) height. Reduced MLA height and excessive pronation may alter lower-limb biomechanics and impair balance performance in PP. This study aimed to investigate the relationship between plantar flexor endurance and postural and tibial sway under varying visual conditions in PP. Methods: In this cross-sectional study, 41 adults with a navicular drop greater than 10 mm were included. Plantar flexor endurance was assessed using the heel rise test. Postural and dominant/non-dominant tibial sway were assessed during single-leg stance under eyes-open and eyes-closed conditions using the wearable IMU-based ALDA Balance Gear, with the sensor positioned at the distal one-third of the tibia for tibial sway and at the L3–L5 level for postural sway. Results: In eyes-open condition, dominant AP tibial sway was moderately negative correlated with dominant heel rise test performance (r = −0.553, p < 0.001). No other significant correlations were observed under either the eyes-open or eyes-closed condition (p > 0.05). Conclusions: These findings suggest that reduced plantar flexor endurance may be associated with lower-limb movement control during single-leg stance in PP. Further studies including healthy controls and broader biomechanical assessments are warranted.