Plantar flexion is a functionally very important movement of the foot. It plays a determining role in activities that serve locomotion.
What is plantar flexion?
Plantar flexion and dorsiflexion are the common names for the movements of the foot in the upper ankle joint. Plantar flexion and dorsiflexion are the common names for the movements of the foot in the upper ankle joint. They take place about an imaginary axis of rotation that passes through both ankles. Although the assignment of the terms extension and flexion in this case always leads to discussion, the use of a directional designation ensures a clear definition. ‘Plantar’ describes a movement of the foot “in the direction of the sole of the foot”, which is additionally described as flexion. What is meant by this is the lowering of the foot. Plantar flexion is performed by the very powerful calf muscles, mainly the triceps surae muscle. This consists of 3 parts, which come from the lower end of the femur and from the back of the tibia. They further unite to form the Achilles tendon and attach to the calcaneus. Plantar flexion has a greater amplitude of motion than dorsiflexion due to an anatomical feature. The inner sides of the ankle, the so-called malleolar fork, limit the upper ankle joint laterally. The other joint partner, the talus pulley, has more lateral range of motion in plantar flexion and can rotate downward to a maximum. In dorsiflexion, the malleolar fork is spread apart until the stabilizing ligaments are maximally taut. The talus is pinched and dorsiflexion is limited.
Function and Purpose
Plantar flexion plays a critical role in activities that involve lifting the body off the ground, which includes many modes of locomotion. An adequate range of motion is the basic requirement for this process, while the executing muscles, the plantar flexors, are responsible for actively overcoming gravity. In walking, plantar flexion terminates the stance leg phase and initiates the subsequent swing leg phase. This activity is particularly accentuated during jumping, climbing, stair climbing and running. All athletic disciplines that involve jumping are characterized by the function of the plantar flexors. As a rule, running and jumping phases alternate in the various sports. In athletics, for example, jumping activities are prominent in the high jump, long jump and triple jump, as well as in 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 manifestation of plantar flexion is pointe dancing in ballet. It requires exceptional flexibility 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 there is muscle activity in that direction. This movement or stabilization process is an important part of balance reactions. It occurs whenever 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 movement of the body with the foot in the free chain, that is, without contact with the ground or any other fixation of the foot. In this case, a medium that presents some resistance is necessary to propel the organism forward. In swimming, for example, this is the frictional resistance of the water. The swimmer uses strong plantar flexion as the end component of the leg stroke to propel him or herself with powerful extension movements.
Diseases and ailments
Typical injuries that affect plantar flexion are fractures in the upper ankle. So-called Weber fractures are common, affecting the lateral malleolus and ligaments in the region. Depending on the severity of the trauma, conservative treatment with immobilization or surgical therapy is performed. Both methods result in a more or less long-lasting impairment of the movements of the foot, especially in the upper ankle joint.An Achilles tendon rupture is a sudden event in which a single blow disables the major muscles of plantar flexion. The remaining plantar flexors are unable to lift the body against gravity, so the functional limitations of this injury are enormous. Surgical treatment is followed by a long rehabilitation period. In order to protect the sutured tendon, the foot must not be brought into dorsiflexion for a considerable period of time so that no traction occurs on the surgical suture. Achilles tendon rupture is a typical sports injury. Hemiplegia due to a stroke often leads to extensor spasticity in the leg. In this case, the tone of the plantar flexors is also greatly increased and the foot cannot be pulled up. Therefore, when walking, it is placed with the forefoot and the sole of the foot reaches the ground only by the pressure of the body weight. Together with the components in the other joints, a typical gait pattern named after Wernicke is formed. Other neurological clinical pictures such as peripheral nerve damage or polyneuropathy lead to a flaccid paralysis of the foot, which also affects plantar flexion. In the case of complete paralysis, the foot can no longer be actively pushed downwards; it virtually falls down due to gravity. This has negative effects on gait stability, which are particularly bad when dorsiflexion is also affected. Plantar flexion, like all movements, can be affected by those conditions that cause systemic muscle loss, such as muscular dystrophies. After prolonged immobilization or inactivity, a pointed foot may develop in which the stretch stimulus is absent due to the disuse of the dorsiflexion of the Achilles tendon. It lingers in approximation for a long time and shortens massively in this position if therapeutic countermeasures are not taken.
