Inclusion Criteria:  Being routinely scheduled for a reconstructive surgical procedure for the following indications or involving the following type of procedure:  Any reconstructive procedure for Pes Planus, Pes Plano-valgus, or Posterior Tibial Tendon Dysfunction Tibio-talar arthrodesis or prosthesis Sub-talar -and/or (partial) Chopart - and/or Triple arthrodesis  Pantalar arthrodesis with or without inclusion of the Chopart joint  Exclusion Criteria:  Age under 18 Need of tools (eg walker or crutches) to walk less than 100m Inability to walk less than 100 m anyway Differences in leg length exceeding 3 cm (measured clinically) Extreme in-or outtoeing Subjects with BMI > 27.5 require very careful further consideration whether or not the obesity prevents the accurate palpation of anatomical landmarks necessary prior to marker placement. This will be judged on an individual basis.