The peroneal artery, [a. peronea] lies deeply along the back part of the leg, close to the fibula : hence its names, peroneal or fibular. Arising from the posterior tibial artery, about an inch below the lower border of the popliteus muscle, it inclines at first obliquely towards the fibula, and then descends nearly perpendicularly along that bone and behind the outer ankle, to reach the side of the os calcis.

In the upper part of its course, this artery is covered by the soleus muscle and the deep fascia, and afterwards by the flexor longus pollicis, which is placed over the artery as far as the outer malleolus; below this point, the vessel is covered only by the common integument and the fascia. The peroneal artery rests at first against the upper part of the tibialis posticus muscle, and afterwards in the greater part of its course on the back of the interosseous membrane, lying close under a projecting ridge of the fibula, — in a depression formed between the membrane and the bone.

Two veins accompany this artery.

Branches

The upper part of the peroneal artery gives numerous muscular branches to the soleus, the tibialis posticus, the flexor longus pollicis, and the peronei muscles, the largest branches being those to the soleus. It likewise furnishes a nutrient artery to the fibula.
Having descended beyond the outer malleolus, the peroneal artery terminates by giving off a series of branches, which ramify on the outer surface of the os calcis. These anastomose with the external malleolar and with the tarsal arteries on the outer side of the foot ; and behind the os calcis with ramifications of the posterior tibial artery.

Anterior peroneal artery [a. peronea ant.] — About two inches above the outer malleolus, the peroneal artery gives off its anterior branch, named anterior peroneal. This immediately pierces the interosseous membrane to reach the fore part of the leg. It then descends along the front of the fibula, covered by the peroneus tertius muscle, and dividing into branches, reaches the outer ankle, and anastomoses with the external malleolar branch of the anterior tibial artery.
It supplies vessels to the ankle-joint, and ramifies on the front and outer side of the tarsus, inosculating more or less freely with the tarsal arteries.
Communicating branch to posterior tibial artery. — Lying close behind the tibia, about two inches from its lower end, a transverse branch will be found connecting the peroneal with the posterior tibial artery, and seeming, by its direction, to pass from the former to the latter vessel.

Peculiarities of the peroneal artery.

The peroneal artery presents occasional deviations from its ordinary condition, in regard to its place of origin, its size, and the extent of its distribution.
This artery has been found to arise lower down than usual, about three inches below the popliteus muscle ; and, on the contrary, it sometimes commences higher up from the posterior tibial, or even from the popliteal artery itself.
When the popliteal artery divides prematurely, the peroneal artery is, in some cases, transferred to the anterior tibial.
Variations in its size constitute the most frequent peculiarities to which the peroneal artery is liable. It more frequently exceeds than falls short of the ordi-
When larger than usual, it is often found to reinforce a small posterior tibial, either by a transverse vessel which joins the diminished artery in the lower part of the leg; or two such reinforcing vessels may be present, one crossing close to the bone, and one over the deep muscles. But the occurrence of a second communicating branch is rare. Again, a large peroneal artery has been observed to take the place of the posterior tibial at the lower part of the leg, and thence onwards to the foot ; the last-named vessel, in such cases, existing only as a short muscular branch at the upper. part of the leg.

The anterior division of the peroneal artery (anterior peroneal) has in some cases more than its ordinary size, and compensates for a small anterior tibial artery in the lower part of the leg or supplies the place of that artery on the dorsum of the foot.
The peroneal artery is rarely smaller than usual. When its anterior division only is wanting, a branch of the anterior tibial supplies the deficiency ; but when the decrease is carried so far that the peroneal artery is expended before reaching the lower part of the leg, a branch of the posterior tibial supplies its place on the outer side of the foot.

In one singular case, recorded by Otto, the peroneal artery was wholly wanting.