Plantar flexion

The Plantar flexion is a functionally very important movement of the foot. It plays a determining role in activities that help you get around.

What is plantar flexion?

Plantar flexion and dorsiflexion are the common names for the movements of the foot in the ankle joint. They take place around an imaginary axis of rotation that runs through the two ankles. Although the assignment of the terms extension and inflection in this case always leads to discussions, a clear definition is guaranteed by using a directional indication.

'Plantar' describes a movement of the foot "in the direction of the sole of the foot", which is also described as flexion. This means lowering the foot. Plantar flexion is performed by the very strong calf muscles, mainly the triceps surae muscle. This consists of 3 parts that come from the lower end of the thigh bone and from the back of the shin. They unite in the further course to form the Achilles tendon and start at the heel bone.

Plantar flexion has a greater range of motion than dorsiflexion due to an anatomical feature. The inner sides of the ankle, the so-called malleolar fork, laterally limit the upper ankle. The other joint partner, the talus roll, has more freedom of movement to the side during plantar flexion and can rotate as much as possible downwards. With dorsiflexion, the malleolar fork is spread apart until the stabilizing ligaments are maximally tensioned. The talus is pinched and the dorsiflexion is limited.

Function & task

Plantar flexion plays a crucial role in activities that lift the body off the ground, which include many types of locomotion. A sufficient range of motion is the basic requirement for this process, while the executing muscles, the plantar flexors, are responsible for actively overcoming gravity. When walking, plantar flexion ends the standing leg phase and initiates the following swing leg phase.

This activity is particularly accentuated when jumping, climbing, climbing stairs and running. All sporting disciplines that involve jumps are shaped by the function of the plantar flexors. As a rule, running and jumping phases alternate in the various sports. In athletics, for example, high jump, long jump and triple jump jump activities are in the foreground, as well as ball sports such as basketball and volleyball. In soccer and handball, plantar flexion is required alternately in running and jumping phases. A very special and extreme form of plantar flexion is the tip dance in ballet. It requires exceptional mobility and a strong ability of the plantar flexors to stabilize the foot with its small contact area.

In some situations, the normal functioning of the movement is reversed, then the foot is fixed and the lower leg moves away from it, or muscle activity occurs in this direction. This movement or stabilization process is an important part of equilibrium reactions. It always appears when the body threatens to fall forward or the forward movement is abruptly stopped because an obstacle or danger may appear.

A completely different mode of action requires the body to move with the foot in the free chain, i.e. without contact with the ground or any other fixation of the foot. In this case a medium is necessary that presents a certain resistance in order to propel the organism forward. When swimming, for example, this is the frictional resistance of the water. The swimmer uses the strong plantar flexion as the end component of the leg kick in order to propel himself forward with powerful stretching movements.

Illnesses & ailments

Typical injuries that impair plantar flexion are fractures in the area of ​​the upper ankle. The so-called Weber fractures, in which the outer malleolus and the ligaments in the region are affected, often occur. Depending on the severity of the trauma, conservative care with immobilization or surgical therapy is carried out. Both methods result in a more or less long-term impairment of the movements of the foot, especially in the ankle joint.

An Achilles tendon rupture is a sudden occurrence in which the main muscles of plantar flexion are overridden in one fell swoop. The remaining plantar flexors are not able to lift the body against gravity, which is why the functional restrictions in this injury are enormous. After the surgical treatment, there is a long rehabilitation phase. To protect the sutured tendon, the foot must not be brought into dorsiflexion for a long time so that there is no tension on the surgical suture. The Achilles tendon rupture is a typical sports injury.

Hemiplegia as a result of a stroke often leads to spasticity in the leg. The tone of the plantar flexors is also greatly increased and the foot cannot be pulled up. When walking, the forefoot is placed on the foot and the sole of the foot only reaches the ground through the pressure of the body weight. Together with the components in the other joints, a typical gait pattern is created that is named after Wernicke.

Other neurological symptoms such as peripheral nerve damage or polyneuropathy lead to flaccid paralysis of the foot, which also affects plantar flexion. In the case of complete paralysis, the foot can no longer be actively pressed down, it almost falls down due to gravity. This has negative effects on gait security, which are particularly bad if the dorsiflexion is also affected.

Plantar flexion, like all movements, can be affected by diseases that cause systemic muscle breakdown, such as muscular dystrophies.

After a long period of rest or inactivity, an equinus foot can develop in which the dorsiflexion of the Achilles tendon is not used to stretch. It stays close for a long time and massively shortens in this position if no therapeutic countermeasures are taken.