Tibialis Anterior

The tendon of the anterior tibial descends along the anterior edge of the internal malleolus and inserts into the lower inner surface of the internal cuneiform bone and base of the first metatarsal bone.

Tibialis Posterior

Its tendon passes down close behind the posterior edge of the internal malleolus, crosses the internal lateral ligament of the ankle, passes under the inferior calcaneonavicular (scaphoid) ligament and in front of the sustentaculum tali to insert into the tubercle of the navicular (scaphoid). From the tubercle its tendon sends slips to all the tarsal bones except the talus (astragalus) and to the bases of the second, third, fourth, and sometimes fifth metatarsal bones.

Flexor Longus Digitorum

Its tendon passes behind the internal malleolus immediately posterior to the tibialis posterior and then curves around the sustentaculum tali to enter the foot, passing forward to insert into the base of the terminal phalanges of the outer four toes.

Flexor Longus Hallucis

This tendon descends across the middle of the posterior part of the ankle-joint and curves forward under the sustentaculum tali. It is the most posterior of the structures running behind the internal malleolus. It lies deeper than the tendon of the flexor longus digitorum, and as it crosses it gives to it a small slip. It then inserts into the base of the terminal phalanx of the big toe.

Peroneus Longus

This tendon overlies the tendon of the peroneus brevis as it passes down immediately behind the external malleolus. It then winds around the outer surface of the os calcis behind the peroneal tubercle to pass obliquely inward and forward across the sole of the foot, in a canal formed by the long plantar ligament and a groove in the cuboid bone, to insert into the base of the first metatarsal bone and internal cuneiform.

Peroneus Brevis

This tendon passes down behind the external malleolus beneath and a little anterior to the tendon of the peroneus longus. It passes in front of the peroneal tubercle and then goes forward to insert into the tuberosity of the fifth metatarsal bone.

Peroneus Tertius

This tendon descends in front of the external malleolus and inserts into the upper surface of the fifth metatarsal bone near its base.

The other muscles of the leg do not support the tarsal arch. In considering the insertions of these tendons it will be seen that the tibialis anterior, peroneus tertius, and peroneus brevis are practically inserted into the convexity of the tarsal arch and tend to support it by pulling it upward. The flexor longus hallucis and flexor longus digitorum run longitudinally beneath the arch and so directly support it. The tibialis posterior and peroneus longus, one from the inner and the other from the outer side, meet and cross on the sole of the foot, thus forming a double sling immediately beneath the arch on which it rests when those muscles contract.

If these muscles, on which the arch directly relies for its support when subjected to the strain of locomotion, are unable to meet the demands made upon them then the strain falls on the ligaments, and as these are intended for static and not dynamic purposes they weaken and give way and the arch descends. To cure such a condition over use must be avoided and the strength of the muscles is to be restored by exercise, massage, electricity, etc.