The posterior tibial artery [a. tibialis postica] is situated along the back part of the leg, between the superficial and deep layers of muscles, being firmly bound down to the latter by the deep fascia.
This artery, extends from the lower border of the popliteus muscle, where it is continuous with the popliteal artery, down to the inner border of the calcaneum, where it terminates beneath the origin of the abductor pollicis muscle, by dividing into the external and internal plantar arteries.
Placed, at its origin, at equal distances between the two sides of the limb, and opposite to the interval between the tibia and fibula, it approaches the inner side of the leg as it descends, and lies behind the tibia ; and at its lower end is placed midway between the inner malleolus and the prominence of the heel. Very deeply seated at its upper part, where it is covered by the fleshy portion of the gastrocnemius and soleus muscles, it becomes comparatively superficial towards its lower part, being covered only by the integument and by two layers of fascia (the annular ligament) behind the inner malleolus. In front, the artery rests successively against the tibialis posticus, the flexor longus digitorum, and, at its lower end, directly on the tibia, and behind the ankle-joint. — The posterior tibial artery is accompanied by two veins. The posterior tibial nerve is at first on the inner side of the artery, but in the greater part of its course the nerve is close to the outer side of the vessel.
Behind the inner ankle, the tendons of the tibialis posticus and flexor longus digitorum lie between the artery and the malleolus; whilst the tendon of the flexor longus pollicis is to its outer side.
The posterior tibial artery furnishes numerous small branches; and, besides these, one large branch, named the peroneal artery, which will be presently described.
Several muscular branches [rami musculares] arise from this artery in its course along the leg, and are distributed principally to the deep-seated muscles in its neighborhood, besides one or two of considerable size to the inner part of the soleus muscle.
The nutrient artery [nutriens tibiae] of the tibia, the largest of this class of arteries in the body, arises from the posterior tibial artery, near its commencement, and, after giving small branches to the muscles, enters the nutrient foramen in the bone, and ramifies on the medullary membrane. This vessel not infrequently the anterior tibial artery. — A communicating branch from the peroneal artery joins the posterior tibial about two inches above the ankle-joint.
Peculiarities of the posterior tibial artery
When the popliteal artery divides prematurely, the posterior tibial, as well as the anterior tibial, is necessarily longer than usual. In some of these cases, it has been observed that the posterior tibial artery does not give origin to the peroneal.
Size. — The posterior tibial artery is not unfrequently diminished in size in different degrees ; this deficiency being compensated for by an enlarged peroneal artery in the leg, or by the anterior tibial artery in the foot. See the account of these arteries respectively.
The posterior tibial is sometimes absent ; in which case the peroneal is enlarged, and takes its place from above the ankle downwards into the sole of the foot.
From Quain's anatomy.