The fibular head is the enlarged, rounded upper end of the fibula bone, one of the two bones in the lower leg. It is situated just below the knee joint on the outer side of the leg, making it easily palpable. This anatomical structure serves as a point of attachment for various soft tissues, including muscles and ligaments. The fibular head plays a role in the stability and movement of the knee joint.
Ligaments Connecting to the Fibular Head
The fibular head serves as an attachment point for several ligaments that contribute to the stability of the knee and the proximal tibiofibular joint. A prominent ligament attaching to the fibular head is the Lateral Collateral Ligament (LCL), also known as the fibular collateral ligament. This cord-like structure originates from the lateral epicondyle of the femur, the lower end of the thigh bone, and extends downward to insert onto the fibular head.
The LCL is a primary stabilizer on the outer side of the knee joint. Its main function involves resisting varus stress—a force that pushes the knee inward—preventing excessive sideways movement. It also helps to prevent external rotation of the tibia relative to the femur. Unlike some other knee ligaments, the LCL does not attach directly to the knee joint capsule or the lateral meniscus, allowing it some independence of movement. The ligament’s tension changes with knee position; it becomes taut when the knee is fully extended and loosens as the knee flexes.
Beyond the LCL, other fibrous connections exist at the fibular head. The tibiofibular ligaments, specifically the anterior and posterior ligaments of the fibular head, connect the fibula to the tibia. These ligaments help to stabilize the proximal tibiofibular joint, the articulation between the fibula and the tibia just below the knee. The popliteofibular ligament, part of the posterolateral corner of the knee, also attaches to the fibula and contributes to knee stability.
Muscles Connecting to the Fibular Head
The fibular head provides attachment sites for several muscles that influence both knee and ankle movements. The biceps femoris is a muscle that inserts onto the fibular head. This muscle, part of the hamstring group at the back of the thigh, has two distinct parts: a long head and a short head.
Its common tendon inserts onto the lateral aspect of the fibular head, with its fibers often splitting around the Lateral Collateral Ligament. The biceps femoris flexes the knee joint. The long head also assists in extending the hip, while both heads contribute to the lateral rotation of the lower leg, especially when the knee is slightly bent. A strong, sudden contraction of the biceps femoris can sometimes cause an avulsion fracture of the fibular head, where a piece of bone is pulled away by the tendon.
Another muscle connected to the fibular head is the Peroneus Longus, also known as the Fibularis Longus. This muscle originates from the fibular head and the upper two-thirds of the lateral surface of the fibula. Its long tendon extends down the leg, passing behind the outer ankle bone, and then courses along the sole of the foot to insert onto the medial cuneiform bone and the base of the first metatarsal bone. The Peroneus Longus everts the foot (turning the sole outward) and assists in plantarflexion (pointing the foot downward). It also supports the arches of the foot.
Other muscles originate near or partially on the fibular head. The Soleus muscle, a large calf muscle, originates from the posterior aspect of the fibular head and the upper part of the posterior fibula. Its action causes plantarflexion of the foot. The Extensor Digitorum Longus, a muscle in the front of the lower leg, originates from the anteromedial aspect of the proximal fibula, as well as the lateral condyle of the tibia and the interosseous membrane. This muscle extends the second through fifth toes and assists dorsiflexion of the foot (pulling the foot upward towards the shin). While the Tibialis Anterior muscle primarily originates from the tibia, it also arises from the adjacent interosseous membrane and intermuscular septum. It is the main dorsiflexor of the ankle and inverts the foot (turning the sole inward).