Biomechanical effects of three types of foot orthoses in individuals with posterior tibial tendon dysfunction

•Custom orthoses decreased foot and hindfoot eversion angle compared to PFO and shoe.•Custom orthoses decreased ankle inversion moment compared to PFO and shoe.•Custom orthoses increased knee abduction moment compared to PFO and shoe.•CVFO acted for a longer duration of change in the stance phase of gait than CFO. Posterior tibial tendon dysfunction (PTTD) is characterized by degeneration of this tendon leading to a flattening of the medial longitudinal arch of the foot. Foot orthoses (FOs) can be used as a treatment option, but their biomechanical effects on individuals with PTTD are not yet fully understood. The aim of this study was to investigate the effects of three types of FOs on gait biomechanics in individuals with PTTD. Fourteen individuals were recruited with painful stage 1 or 2 PTTD based on Johnson and Strom’s classification. Quantitative gait analysis of the affected limb was performed in four conditions: shoes only (Shoe), prefabricated FO (PFO), neutral custom FO (CFO) and custom varus FO (CVFO) with a 5° medial wedge and a 4 mm medial heel skive. A curve analysis, using 1D statistical parametric mapping, was undertaken to assess differences in lower limb joint motion, joint moments and muscle activity over the stance phase of gait across conditions. Decreased hindfoot eversion angles, decreased ankle inversion moments and increased ankle eversion moments were observed with custom FOs compared to the Shoe and PFO conditions (p