The fibula is one of the two bones located in the lower leg. Positioned on the lateral side of the leg, it runs parallel to the larger tibia, often referred to as the shinbone. While slender compared to the tibia, the fibula performs distinct and important functions, providing structural support and facilitating movement for the body’s lower leg and ankle.
Key Roles in Ankle Stability
The fibula contributes to the stability of the ankle joint, specifically the talocrural joint. Its distal end forms the lateral malleolus, a bony protrusion felt on the outside of the ankle. This lateral malleolus articulates with the talus bone of the foot and the tibia, creating a secure bony enclosure.
This articulation, along with strong ligaments like the lateral collateral ligaments, helps prevent excessive side-to-side movement and rotation of the ankle. These connections maintain proper alignment of the foot and lower leg during activities like standing, walking, and running. The fibula acts as a lateral buttress, stabilizing the ankle joint.
Muscle Attachment and Lower Leg Movement
Beyond its role in stability, the fibula serves as an attachment point for several lower leg muscles. These muscles originate from or insert onto various surfaces of the fibula, including its head, shaft, and lateral malleolus. This arrangement allows the fibula to act as a lever for muscle action, enabling a wide range of foot and ankle movements.
Muscles attached to the fibula are involved in actions such as eversion (turning the sole of the foot outwards) and plantarflexion (pointing the toes downwards). Other muscles facilitate dorsiflexion, which lifts the toes upwards. These muscular attachments control foot position, maintain balance, and propel the body during locomotion.
Non-Weight Bearing Support
The fibula differs from the tibia in its role concerning body weight support. It is not a primary weight-bearing bone, carrying only a small percentage of the body’s weight, typically ranging from about 6% to 17% of an axial load. Despite this, the fibula provides important structural integrity to the lower leg. It functions as a scaffold, helping to maintain the overall shape and alignment of the lower leg alongside the tibia.
The fibula also assists in absorbing rotational forces that occur during movement. Its connection to the tibia via the interosseous membrane, a fibrous sheet, helps to distribute forces and provide secondary support to the lower leg.
Impact of Fibula Injuries
When the fibula is injured, its functions can be compromised, affecting mobility and stability. Fractures, especially those involving the lateral malleolus at the ankle, can disrupt the ankle joint’s structural integrity. Such injuries may also affect ligaments connecting the fibula to the tibia and talus, impairing ankle stability.
Injuries to the fibula can also affect muscle attachment points, impacting lower leg and foot movement. Consequences, like ankle fractures or high ankle sprains, include pain, swelling, and difficulty bearing weight. These impairments limit daily activities, highlighting the fibula’s importance despite its non-weight-bearing role.