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

Change in Lateral Patellar Tilt

Lateral patellar tilt will be measured in degrees on standardized weight-bearing cone beam CT images. The measure describes the sideways tilt of the kneecap in relation to the thigh bone. It is defined as the angle between the transverse axis of the patella and the posterior condylar axis of the femur. Measurements will be performed for each foot posture condition: natural foot posture, barefoot correction with foot orthoses, and correction with foot orthoses inside a neutral running shoe. Measurements will be assessed at both 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Bisect Offset

Bisect offset will be measured as a percentage on standardized weight-bearing cone beam CT images. The measure describes the sideways position of the kneecap in relation to the groove of the thigh bone. It is defined as the percentage of lateral displacement of the midpoint of the patella from the midpoint of the trochlear groove. Higher percentages indicate greater lateral displacement of the kneecap. Measurements will be performed for each foot posture condition: natural foot posture, barefoot correction with foot orthoses, and correction with foot orthoses inside a neutral running shoe. Measurements will be assessed at both 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Tibial Tuberosity-Trochlear Groove Distance

Tibial tuberosity-trochlear groove distance will be measured on standardized weight-bearing cone beam CT images and reported in millimeters. The measure describes the side-to-side distance between the tibial tuberosity, where the patellar tendon attaches on the shin bone, and the center of the trochlear groove of the thigh bone, where the kneecap moves. Measurements will be performed for each foot posture condition: natural foot posture, barefoot correction with foot orthoses, and correction with foot orthoses inside a neutral running shoe. Measurements will be assessed at both 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Transmalleolar Rotation Across Foot Posture Conditions

Transmalleolar rotation will be measured in degrees on standardized weight-bearing cone beam CT images. The measure describes the rotation of the ankle axis in relation to the long axis of the foot. The ankle axis is defined as a line through the medial and lateral malleoli. The foot axis is defined by an adjusted sagittal foot reference plane derived from calcaneal and metatarsal head landmarks on cone beam CT. Transmalleolar rotation is calculated as the angle between the malleolar line and this foot axis. Positive values indicate external rotation relative to the foot axis, and negative values indicate internal rotation. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion.

Change in Tibial Rotation Across Foot Posture Conditions

Tibial rotation will be measured in degrees on standardized weight-bearing cone beam CT images. The measure describes the rotation of the shin bone in relation to the long axis of the foot. It is defined as the angle between a line tangent to the posterior surface of the proximal tibia and the foot axial rotation reference. The foot axial rotation reference is an adjusted sagittal foot plane derived from calcaneal and metatarsal head landmarks on cone beam CT. Positive values indicate external rotation relative to the foot axis, and negative values indicate internal rotation. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Femoral Rotation Across Foot Posture Conditions

Femoral rotation will be measured in degrees on standardized weight-bearing cone beam CT images. The measure describes the rotation of the thigh bone in relation to the long axis of the foot. It is defined as the angle between a line tangent to the posterior femoral condyles and the foot axial rotation reference. The foot axial rotation reference is an adjusted sagittal foot plane derived from calcaneal and metatarsal head landmarks on cone beam CT. Positive values indicate external rotation relative to the foot axis, and negative values indicate internal rotation. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Navicular Plantar Position Across Foot Posture Conditions

Navicular plantar position will be measured in millimeters on standardized weight-bearing cone beam CT images. The measure describes the vertical position of the navicular bone, which is a bone on the inner side of the midfoot and an indicator of medial arch position. It is defined as the perpendicular distance between the lowest point of the navicular bone and the tripod-adjusted axial foot plane. This reference plane is based on the plantar support points of the foot. Greater values indicate that the navicular bone is positioned farther from the plantar reference plane. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Navicular Medial Displacement Across Foot Posture Conditions

Navicular medial displacement will be measured in millimeters on standardized weight-bearing cone beam CT images. The measure describes the side-to-side position of the navicular bone, which is a bone on the inner side of the midfoot and an indicator of foot pronation and medial arch position. It is defined as the perpendicular distance from the most medial point of the navicular bone to the adjusted sagittal foot reference plane. This reference plane is derived from calcaneal and metatarsal head landmarks on cone beam CT and approximates the long axis of the foot. Greater values indicate that the navicular bone is positioned farther medially relative to the foot reference plane. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Change in Foot Axial Rotation Across Foot Posture Conditions

Foot axial rotation will be measured in degrees on standardized weight-bearing cone beam CT images. The measure describes the toe-in or toe-out orientation of the foot. It is defined as the angle between the adjusted sagittal foot reference plane and the global sagittal plane. The adjusted sagittal foot reference plane is derived from calcaneal and metatarsal head landmarks and approximates the long axis of the foot. Positive values indicate external rotation, or toe-out, and negative values indicate internal rotation, or toe-in. Measurements will be performed for each foot posture condition at 0 and 20 degrees of knee flexion. Change will be reported as the within-participant difference between foot posture conditions.

Baseline Femoral Anteversion

Femoral anteversion will be measured in degrees on the baseline weight-bearing cone beam CT scan. The measure describes the forward rotation of the femoral neck in relation to the distal femur. It is defined as the angle between the femoral neck axis and the posterior condylar axis of the distal femur. The femoral neck axis is defined as a line connecting the center of the femoral head and the center of the femoral neck. The posterior condylar axis is defined as a line tangential to the most posterior aspects of the medial and lateral femoral condyles. Positive values indicate increased femoral anteversion. This measure will be used to describe baseline femoral morphology and to account for anatomical variation that may influence lower-limb rotational alignment.