Lateral malleolus

Of the Lateral malleolus is the thickened end of the fibula that is involved in the upper ankle. This so-called outer ankle creates the conditions for the flexion and extension of the foot in a dorsal and plantar direction. Fractures of the ankle joint are the most common broken bones and often correspond to a malleolus fracture.

What is the lateral malleolus?

The fibula is one of two lower leg bones and rests against the shin. It is a typical long bone, which is thickened at the lower end. The thickening at the bottom of the fibula is called the lateral malleolus.

More precisely, the lateral malleolus is the lateral protrusion of bone at the distal end of the fibula. The anatomical structure, together with the medial malleolus, is involved in the formation of the so-called malleolar fork, which surrounds the ankle bone in the form of a fork and ends in the ankle joint. The two main joints of the human foot are known as the ankle and can move the foot on three different levels. The human lateral malleolus is even more specifically involved in the lateral malleolus. The structure is different from the fibrous structures of most animals.

Ruminants carry what is left of a separate bone at the lower end of the fibula, the so-called malleolar bone. Horses have fibula that are completely fused with the shin. Your fibula is only formed as a separate bone in the upper half of the lower leg. The lateral malleolus is also known as the fibula tip or fibula bone.

Anatomy & structure

As a long bone, the fibula is a long bone made up of two bone ends called the epiphyses. There is also a shaft of bone: the so-called diaphysis. The transition from the epiphysis to the diaphysis is called the metaphysis. The epiphyses are made up of a network of trabeculae that align with the directions of the forces acting on them.

The trabeculae form a spongy bone substance and carry cavities with red bone marrow between each other. The substantia spongiosa is covered on the outside with compact bone substance and has a layer of hyaline cartilage on the joint surfaces. At the diaphysis there is an artery for supplying bones. Except for the cartilaginous joint surfaces, the entire area of ​​tubular bones is covered by the periosteum, the so-called periosteum.

The lateral malleolus forms the lower end of the long bone fibula and has a thickening. A furrow runs over the outside of the bone: the lateral malleolar sulcus, which carries the tendons of the peroneus muscle. On the inside there is a joint surface, which is called the facies articularis malleoli and which creates a connection with the talus. With these structures, the lateral malleolus participates in the ankle and also forms a pit. Ligaments attach to this pit-shaped lateral malleoli fossa.

Function & tasks

The anatomical structure of the lateral malleolus or fibula is significantly involved in the formation of the ankle and outer ankle. The most important functions of the fibula process include, in particular, the individual forms of movement of the ankle in the upper ankle. Every joint has certain axes of movement. The human ankle joint has a total of three different axes of movement and can therefore perform six different forms of movement of the foot.

Inversion, eversion, supination and pronation take place in the lower ankle. The extent of these movements differ depending on the type of movement. The lateral malleolus does not play a role for the lower, but rather for the upper ankle, where movements take place on one axis. The upper ankle is most likely a hinge joint. The lateral malleolus in this joint creates the conditions for two different movements of the foot: for extension and flexion in a dorsal or plantar direction. Without the lateral malleolus, for example, the foot could neither bend towards the back of the foot nor towards the sole of the foot. Nor would it be possible for him to stretch out from these positions.

The individual types of diffraction have different degrees. The flexion of the foot towards the back of the foot shows a range of motion of 30 degrees from the zero position. The flexion towards the sole of the foot only encompasses 20 degrees. The types of movement of the ankle play a major role in everyday movement sequences. Without the ability to move in the ankle, a person could neither walk, run nor jump well. Because the lateral malleolus is involved in the ankle joint, its structure is also irreplaceable for the everyday movements mentioned.

Diseases

With regard to the lateral malleolus, ankle fractures and deformities play a role in clinical practice. The ankle is exposed and exposed to heavy loads every day. Ankle injuries are therefore not uncommon.

Injuries to the ligamentous apparatus in the lateral malleolus are among the most common injuries to the upper ankle and in most cases result from a twisted ankle. Such phenomena can, for example, overstretch the ligaments in the pit of the lateral malleolus or, in the worst case, tear them. All ligament injuries in this area are summarized as ankle sprains. In addition to pain and movement pain, limited flexions and extensions of the foot characterize a distortion in this area. In addition to ligament injuries, fractures of the upper ankle are also common.

In adults, such fractures are even the most common fractures. A fracture of the ankle joint is usually preceded by a dislocation in the joint. The bone loosens from its articulated connection and the outer ankle breaks. The sprained fracture is noticeable through pain and restricted mobility in the upper ankle. If the fracture is not treated in time, permanent malpositions of the ankle can result. Such misalignments can permanently restrict the ability to move and also promote arthrosis in the upper ankle.