The peroneal muscles, also known as the fibularis muscles, are a group of three muscles located on the outer side of the lower leg. These muscles play an important role in the movement and stability of the foot and ankle. Their actions allow for various foot motions and contribute to overall balance during daily activities.
Anatomical Overview
The peroneal muscle group consists of the fibularis longus, fibularis brevis, and fibularis tertius. The fibularis longus originates from the upper fibula. Its tendon travels down the leg, wraps around the outer ankle bone, and crosses underneath the foot to insert into the first metatarsal and medial cuneiform bones.
The fibularis brevis lies beneath the fibularis longus and originates from the lower fibula. Its tendon also passes behind the outer ankle bone, inserting into the base of the fifth metatarsal bone. The fibularis tertius is a smaller muscle, originating from the lower fibula and interosseous membrane. Its tendon inserts onto the dorsal surface of the fifth metatarsal bone.
Key Roles in Movement
The primary actions of the fibularis longus and brevis muscles are eversion and plantarflexion of the foot. Eversion involves turning the sole of the foot outwards, away from the body’s midline. This movement helps navigate uneven terrain and maintain balance. Both muscles work together to achieve this outward rotation, with the fibularis longus also assisting in depressing the first metatarsal.
Plantarflexion, the action of pointing the foot downwards, is also performed by the fibularis longus and brevis muscles. This movement aids in pushing off the ground during walking or running. The fibularis longus contributes to this pushing motion. The fibularis tertius, while also contributing to eversion, primarily functions in dorsiflexion, which is pulling the foot upwards towards the shin.
Contribution to Stability and Locomotion
The peroneal muscles maintain ankle stability, particularly during dynamic movements. Their ability to evert the foot helps to counteract excessive inversion, the inward rolling of the ankle that often leads to sprains. By providing dynamic support to the ankle joint, they protect ligaments from injury. This protective mechanism is important when walking or running on unstable surfaces.
These muscles play a role in efficient locomotion by adapting the foot to various ground conditions. As the foot makes contact with the ground, the peroneal muscles adjust its position, allowing for effective shock absorption and propulsion. They contribute to the controlled lowering of the foot after toe-off and prepare it for the next ground contact. This continuous adjustment helps maintain balance and reduces the risk of falls.