The fibularis muscles, also known as peroneus muscles or peroneals, constitute an important group of muscles located in the lower leg. This group is typically composed of three distinct muscles: the fibularis longus, fibularis brevis, and fibularis tertius. While they share a common name and contribute to foot movement, they exhibit differences in their location, nerve supply, and specific actions. Understanding this group provides a broader context
for the role of the fibularis longus in human anatomy.
Lateral and Anterior Compartment Divisions
The fibularis longus and fibularis brevis muscles are both situated within the lateral compartment of the leg. This shared location means they are supplied by the fibular artery and, importantly, by the superficial fibular nerve. Their anatomical proximity and shared nerve supply contribute to their coordinated actions in foot movement. In contrast, the fibularis tertius muscle is found in the anterior compartment of the leg. Its distinct location also means it receives its blood supply from the anterior tibial artery and is innervated by the deep fibular nerve. These differences in compartment and nerve supply highlight the specialized roles each muscle plays within the lower leg.
Diverse Actions in Foot Mechanics
Despite their different locations and nerve supplies, all three fibularis muscles share a common action: they move the sole of the foot outward, away from the midline of the body. This movement is medically termed eversion. However, their other primary actions on the foot differ. The fibularis longus and fibularis brevis muscles are both responsible for extending the foot downward, a movement known as plantar flexion. This action is crucial for activities like standing on tiptoes or pushing off the ground when walking or running.
Conversely, the fibularis tertius muscle performs an opposing action; it pulls the foot upward toward the body, a movement called dorsiflexion. This differentiation in action allows for a wide range of precise foot movements. The fibularis longus, being the longest and most superficial of the three, plays a prominent role in both eversion and plantar flexion, contributing significantly to the stability and mobility of the ankle and foot. The coordinated effort of these three muscles ensures the foot can adapt to various terrains and movements, providing both flexibility and support.
Variations Within the Fibularis Group
The fibularis muscles are known for their variability, and several anatomical variants are occasionally present in individuals. These can include additional muscles such as the peroneus digiti minimi and the peroneus quartus. The peroneus quartus, for instance, is often more closely associated with the tendons of the extensor digitorum longus and may even send a small tendon to the fifth, or little, toe. These variations underscore the complexity and adaptability of human anatomy, where additional structures can sometimes contribute to the intricate network of muscles and tendons controlling foot movement.
