It marks the lower limit of the insertion of the Popliteus, serves for the attachment of the fascia covering this muscle, and gives origin to part of the Soleus, Flexor digitorum longus, and Tibialis posterior muscles.
12.
Plantarflexion of the foot : Primary muscles for plantar flexion are situated in the Posterior compartment of leg, namely the superficial Gastrocnemius, Soleus and Plantaris ( only weak participation ), and the deep muscles Flexor hallucis longus, Flexor digitorum longus and Tibialis posterior.
13.
The two portions join at an acute angle, and end in a flattened band which is inserted into the lateral margin and upper and under surfaces of the tendon of the flexor digitorum longus, forming a kind of groove, in which the tendon is lodged.
14.
The sheath for Flexor hallucis longus reaches up to the level of the tip of the malleolus, while that for the Flexor digitorum longus is slightly higher; the former is continued to the base of the first metatarsal, but the latter stops opposite the first cuneiform bone.
15.
Opposite the bases of the first phalanges, each tendon divides into two slips, to allow of the passage of the corresponding tendon of the flexor digitorum longus; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying long Flexor tendon.
16.
The "'lumbricals "'are four small skeletal muscles, accessory to the tendons of the flexor digitorum longus and numbered from the medial side of the foot; they arise from these tendons, as far back as their angles of division, each springing from two tendons, except the first.
17.
The middle third of the posterior surface is divided by a vertical ridge into two parts; the ridge begins at the popliteal line and is well-marked above, but indistinct below; the medial and broader portion gives origin to the Flexor digitorum longus, the lateral and narrower to part of the Tibialis posterior.
18.
Enumerated from the medial side, the four canals which it forms transmit the tendons of the tibialis posterior and flexor digitorum longus muscles; the posterior tibial vessels and tibial nerve, which run through a broad space beneath the ligament; and lastly, in a canal formed partly by the talus, the tendon of the flexor hallucis longus.
19.
The flexor retinaculum sends fibrous septa to the bone to form four separate osseofibrous tunnels for the following structures which are from anterior to posterior : the tendon and the synovial sheath of tibialis posterior, the tendon and synovial sheath of flexor digitorum longus, the posterior tibial vessels and their tibial nerves and the tendon and synovial sheath of flexor hallucis longus.
20.
The "'posterior surface "'presents, at its upper part, a prominent ridge, the popliteal line, which extends obliquely downward from the back part of the articular facet for the fibula to the medial border, at the junction of its upper and middle thirds; it marks the lower limit of the insertion of the Popliteus, serves for the attachment of the fascia covering this muscle, and gives origin to part of the Soleus, Flexor digitorum longus, and Tibialis posterior.
