The peroneus longus tendon is a stout band of connective tissue that passes behind the lateral malleolus (network of nerves and muscles around the ankle) to insert the peroneus longus muscle at the foot. The peroneus longus muscle is the evertor muscle, meaning to turn the sole of the foot outward. It is a long, strap-like muscle located on the outside of the lower leg. It connects the tibia and the fibula (the lower leg bones) to the foot. It functions in eversion of the foot, assists in plantar flexion (moving it downward), and helps support the arch of the foot.