flexor digitorum longus
flexor digitorum longus muscle

It lies on the posterior aspect of the tibialis posterior and flexor digitorum longus muscles, and medial to the belly of flexor hallucis longus.

The tendon of the flexor digitorum longus muscle forms two: the crural chiasm (with the tendon of the tibialis posterior muscle) and the plantar chiasm (with the tendon of the flexor hallucis longus muscle).

On the other side of the fascia are the tibialis posterior muscle, the flexor digitorum longus muscle, and the flexor hallucis longus muscle, along with the posterior tibial artery and posterior tibial vein and the tibial nerve.