Also known as the peroneus brevis, the fibularis brevis is a short, peroneal muscle that lies just underneath the peroneus longus muscle. The peroneal muscles extend along the outer portion of the lower leg and foot.
The peroneus brevis attaches to the lower two-thirds of the fibula bone and the fifth metatarsal bone of the foot. The superficial peroneal nerves (L5 and S1) are the power source behind this muscle.
The peroneus brevis plays an important role in the motor functions of the foot. The muscle assists in the flexion that moves the ball of the foot away from the body. The muscle also assists with the eversion (turning outward) of the inner portion of the foot. Each of these movements helps keep the body balanced when walking on uneven surfaces.