Dorsal extension is the term used to describe regular specific movements of the hand and foot. At the toes and at the spine the term appears only alternatively, more usual are there other designations.
What is dorsiflexion?
Dorsiflexion is the term used to describe regular specific movements on the hand and foot. The term dorsiflexion comes from anatomical nomenclature. It is composed of two Latin vocabulary words. ‘Dorsal’ indicates the direction of the movement: ‘directed toward the back’ (‘dorsum’). It runs from the front down to the back up. ‘Extension’ means ‘stretching‘ and is the opposite of ‘flexion’ (bending). As a term, dorsal extension is used to extend the hand and foot. It describes the lifting of the respective two body parts in the wrist and in the upper ankle joint, respectively. The imaginary axis of movement runs across the body through the knuckles in the lower leg and through the proximal carpus. Starting from the zero position, the hand or foot describe a circular path on which they approach the forearm or lower leg. A special feature of the foot is that the zero position is the 90° position. The opposite direction on the hand is called palmar flexion and on the foot plantar flexion. The usual definition of flexion and extension causes difficulties with dorsal extension. It is not accompanied by an increase of the joint angle as described in other joints. For this reason, the term dorsiflexion is sometimes used in the literature. For the movements in the toes and spine, extension has become the usual term; dorsiflexion is rarely used there.
Function and task
Dorsiflexion has an important role in many activities, both as a free movement and as a stability component. All activities in which the hand grasps and holds something require a stable position in the wrist in slight dorsiflexion. This functional position provides the joint with the necessary stability, which is the basis for optimal strength development of the fingers. Not only does holding heavy weights challenge the muscles active in this position, but more often functions with little load, while simultaneously moving the entire arm and fingers. Typical examples are long typing activities with the keyboard or using the mouse. As a free movement, dorsiflexion in the wrist plays an important role in all reaching movements of the hand. The entire joint chain is brought into a pre-stretched position, allowing the subsequent throwing or striking motion to be launched more efficiently. A typical movement in sports in which the entire chain from the shoulder joint to the elbow joint to the wrist and fingers is brought into a pre-stretched position is the lunge in volleyball before the smash. The same is true for the overhead volley in tennis, except that the fingers are closed by the grip. Dorsiflexion on the foot has its most important function in walking. Together with the toe extensors, the foot is lifted in the swing leg phase so that the leg can be placed forward freely and without interference. Increased this form of activity occurs when the pace is increased. When running and especially sprinting, the leg and foot are lifted off the ground significantly more than when walking. The function of the performing muscles is thus challenged even more.
Diseases and ailments
Lifting of the hand and foot can be affected by various injuries or diseases. One specific cause of weakness in the executing muscles and a resulting deficit in dorsiflexion is nerve lesions. Damage to the radial nerve leads to failure of the dorsal extensors of the hand and the appearance of the so-called drop hand. In the case of complete paralysis, lifting is no longer possible at all; in the case of incomplete paralysis, residual functions are still present. The cause of nerve damage can be injuries such as bone fractures, but also pressure loads caused by a cast that is too tight and neurological diseases such as hemiplegia or polyneuropathy. The complementary phenomenon on the foot is the so-called foot jack weakness. It can be caused by a lesion of various nerve branches supplying the dorsal extensors. Causes can be the same as in the arm.More often than in the upper extremity, pressure damage due to a herniated disc is the reason for this loss of function, as it presses on the nerve root. The lack of or limited dorsiflexion is particularly noticeable when walking or running. The foot cannot be lifted or lifted only slightly and drags across the ground in the swing leg phase. It becomes dangerous if sensitivity is disturbed at the same time. Sensitivity disorders of this kind occur in neurological disorders, such as stroke, polyneuropathy and as a result of a herniated disc. All forms of muscle diseases sooner or later lead to restricted dorsiflexion of the hand and foot. These include muscular dystrophies and amyotrophic lateral sclerosis. A special form of restriction of foot mobility is the so-called pointed foot. Due to immobilization, but more often due to a long period of inactivity, the Achilles tendon shortens massively. As a result, the movement into dorsiflexion is increasingly reduced and at some point is no longer possible. A typical overuse syndrome affecting the dorsal extensors of the hand is the so-called tennis elbow, in which the origins of the muscles are painfully irritated.
