This study aims to investigate the effects of pes planus deformity on gait spatiotemporal parameters and pelvic kinematics during walking on different inclines. Participants will include healthy adults aged 18-35 years with flexible bilateral pes planus and normal body mass index. Pes planus severity will be evaluated using the Jack's toe-raise test and the navicular drop test. Gait parameters such as walking speed, cadence, stride length, stance and swing phase percentages, gait cycle duration, as well as pelvic tilt, obliquity, and rotation symmetry will be measured using the BTS-G wireless sensor system. Assessments will be performed on both flat and inclined treadmill conditions. The findings are expected to provide new insights into the biomechanical adaptations of pes planus during walking and contribute to the development of an individualized rehabilitation protocol.

This study will evaluate the effects of pes planus deformity on gait spatiotemporal parameters and pelvic kinematics during walking on flat and inclined surfaces. Flexible pes planus will be confirmed with Jack's toe-raise test, and severity will be assessed using the navicular drop test.

Healthy adults aged 18-35 years with bilateral flexible pes planus and normal BMI will be included. Exclusion criteria are lower extremity injury or surgery in the last 6 months, chronic ankle instability, other musculoskeletal disorders, or orthotic use.

Gait will be assessed with the BTS-G wireless sensor system, recording speed, cadence, stride length, stance and swing phase percentages, gait cycle duration, pelvic tilt, obliquity, and rotation symmetry. Participants will walk in standard sports shoes on level and inclined treadmill conditions. Data will be analyzed to determine biomechanical differences across surfaces.

The findings may provide insights into how pes planus influences gait and contributes to rehabilitation and footwear strategies.

Inclusion Criteria: **Pes Planus Group

• Age 18-35 years

• Normal BMI

• Bilateral, asymptomatic flexible pes planus

• Navicular drop ≥10 mm (both feet)

• Willing and able to provide informed consent and complete the procedure.

  **Healthy Control Group

• Age 18-35 years

• Normal BMI

• No pes planus deformity; otherwise healthy and able to complete procedures

Exclusion Criteria:** both groups

• Use of orthotics/insoles
• Musculoskeletal disorders affecting gait (other than pes planus in the case group)
• Lower extremity injury or surgery within the last 6 months
• Chronic ankle instability
• Any treatment related to the lower extremity/pes planus within the last 6 months

Adults aged 18-35 years with normal body mass index will be recruited. The study will include two groups:

Flexible Pes Planus Group: Participants with bilateral, asymptomatic, flexible pes planus confirmed by Jack's toe-raise test and a navicular drop ≥10 mm.

Healthy Control Group: Participants without pes planus deformity and with normal foot posture.