Effect of Foot Orthoses on Kneecap Position in Adults With Flexible Flatfoot

Does Correction of Pronated Foot Posture Alter Patellofemoral Alignment? A Weight-Bearing Cone Beam CT Proof-of-Concept Study in Individuals With Flexible Flatfoot

This study will look at whether correcting a flat foot position with foot orthoses, also called shoe inserts, can change the position of the kneecap during standing.

Some people with flexible flatfoot have a foot position that may affect how the lower leg and knee are aligned. This may influence the way the kneecap sits or tilts in relation to the thigh bone. Foot orthoses are often used for knee and foot problems, but it is not clear whether they directly change kneecap position when a person is standing and bearing weight.

The study will include adults with flexible flatfoot. Each participant will have low-dose, three-dimensional weight-bearing cone beam CT scans while standing in different foot positions: their natural foot position, with foot orthoses, and with foot orthoses inside a neutral running shoe. Scans will be performed with the knees straight and slightly bent.

The main hypothesis is that correcting a pronated flat foot position with foot orthoses will reduce sideways tilt and outward shift of the kneecap compared with the participant's natural foot position. The study will also examine whether changes in foot position are accompanied by changes in lower-limb rotation.

This study does not test whether foot orthoses reduce pain. Instead, it is designed to understand the immediate mechanical effect of foot correction on kneecap position.

Inclusion criteria

• Age 18-35 years

• Pronated foot posture, defined as a Foot Posture Index (FPI) score of ≥ +6, including a calcaneal frontal plane position sub-score of +2. 25,26

  ○ A trained examiner will assess FPI; inclusion is based on the right foot.

• Flexible flatfoot deformity, defined as restoration of the medial longitudinal arch during lift of the first toe.

Exclusion criteria

• Knee pain during standing or at 20° knee flexion
• Clinical signs of tibiofemoral instability
• Previous knee or foot surgery
• History of patellar dislocation
• Neuromuscular disease
• Pregnancy
• Inability to perform full weight bearing during scans