The purpose of the current work is to determine the prevalence of calf muscle tightness in asymptomatic flat foot subjects.

Pes planus (Flat foot) deformity is a common chronic foot and ankle condition characterized by flattening of the medial longitudinal arch (MLA), rearfoot valgus and abduction of the midfoot on the hind foot.

A flexible pes planus is caused by tibialis posterior dysfunction, ligament loosening, Achilles tendon shortening, and weakness of the intrinsic foot muscles. These deformations cause plantar flexion and adduction of the talus bone and valgus of the calcaneus bone.

Up to our knowledge:

1. No previous studies investigated whether all flat foot is usually associated with gastrocnemius and soleus muscle tightness or it is a random association.
2. And whether tightness of gastrocnemius and soleus is highly found in all cases of flat foot.

Consequently this study is conducted.

Inclusion Criteria:

1. Subjects should have flexible flat foot.
2. Age between 20 and 40 years.
3. Navicular drop of more than 10 mm.
4. Body Mass Index from 18.5 kg/m2 to 29.9 kg/m2.
5. Subjects will sign the written consent form after the aim and methods of the study are explained clearly.

Exclusion Criteria:

1. Subjects with history of foot and ankle surgery, trauma, fracture or dislocation.
2. Subjects with congenital deformities in the ankle and foot.
3. Subjects with systemic or neurologic diseases that could affect lower extremity biomechanics.

Subjects with flexible flat foot aged between 20 and 40 years old . They should have navicular drop more than 10 mm and their body mass index is between 18.5 kg/m2 to 29.9 kg/m2.