anterior intermuscular septum of leg anterior intermuscular septum of leg the anterior intermuscular septum of leg or anterior crural intermuscular septum is a band of fascia which separates the lateral from the anterior compartment of leg. anterior intermuscular septum of legcross-section through middle of leg.detailsidentifierslatinseptum intermusculare cruris anteriusta98a04.7.03.022ta22709fma58755anatomical terminology the deep fascia of leg gives off from its deep surface, on the lateral side of the leg, two strong intermuscular septa, the anterior and posterior peroneal septa, which enclose the peroneus longus and brevis, and separate them from the muscles of the anterior and posterior crural regions, and several more slender processes which enclose the individual muscles in each region.