Biomechanical and Morphological Characterization of PTTD

Posterior tibial tendon dysfunction (PTTD) is a progressive condition of the tendon of the tibialis posterior muscle with symptoms of tendinopathy or even rupture. Functionally, it is associated with the inability to lock the mid foot and thus manifests itself as a main contributor to adult acquired flatfoot deformity. Concerning treatment, clinical decision making is currently based on a classification integrating various parameters as pain, flexibility of the foot joints, the condition of the posterior tibial tendon assessed through ultrasound imaging and radiographic assessment of arthritic changes. Surprisingly, this classification does not consider any morphologic characteristics (the shape of a bone or joint) or functional, biomechanical characteristics of the foot and ankle, i.e. based on kinematics (e.g. range of motion) and/or kinetics (center of pressure, angular velocity, moment, power absorption and power generation of a joint). Detailed biomechanical characteristics of the foot and ankle can be reliably collected by instrumented gait analysis wherein a 3D camera system is combined with a force plate and plantar pressure platform. Kinematic studies in the field of PTTD typically considered the foot as a structure consisting of three segments: hind foot, forefoot and hallux. Consequently, the mid foot segment (the Chopart and Lisfranc joints) has been neglected, although it is this segment that is particularly affected in PTTD patients. The aim of this research is to overcome the limitations of the current classification system and treatment of PTTD patients, by complementing the current standard-of-care clinical assessment with better insight in the pathologic changes that occur in PTTD patients.

Inclusion criteria: * Patient groups: * Posterior tibial tendon dysfunction (all clinical stages) * Age 18-675 year * ICF obtained * Control group: * No pain complaints * No pes plano valgus, PTTD or pes cavo varus or other foot and ankle pathology * Age 18-75 year * ICF obtained Exclusion criteria patient and control groups: * Being younger than 18 years * Inability to walk without mobility aids * Inability to walk \< 100 meter * Difference in leg length \> 3cm * Subjects with BMI\>30 kg/m², due to less accurate gait analysis by absence of anatomical landmarks * Subjects unable to perform a gait analysis * Any medical condition possibly affecting normal gait. * Pregnancy: at the start or during the study