Pronation and supination
Pronation and supination are movements that define the orientation of the palm, forearm, or foot in space. Pronation and supination are important movements that help us do various daily activities. The definition of these movements differs in the upper and lower limbs. Thus, we will discuss these movements separately for the upper and lower limbs.
Pronation and supination in the upper limb (forearm and hand)
In the upper limb, pronation is the rotatory movement during which the palm and forearm face downward. The forearm is the part of the upper limb below the elbow joint. It has two bones: radius and ulna. Two joints are involved in pronation and supination of the hand and forearm. These are the proximal and the distal radioulnar joints formed between the upper and lower ends of the radius and ulna, respectively. A tough membrane of connective tissue, called the interosseous membrane, keeps the forearm bones bonded during pronation and supination. The main muscles enabling pronation of the upper limb are pronator teres, pronator quadratus, and brachioradialis muscles. Supination is mainly facilitated by supinator and biceps brachii muscles.
Injury to the upper limb can damage any of the nerves or muscles involved in pronation and supination. Birth trauma can result in the injury to various nerves (brachial plexus), including the musculocutaneous nerve that supplies biceps brachii muscle. This condition is called Erb palsy. Since biceps brachii facilitates supination and flexion, the nerve injury makes the forearm pronated and extended (waiter’s tip position).
A fracture of the upper end of the ulna along with the dislocation of the upper end of the radius (Monteggia fracture) can occur when a person falls on the outstretched hand. This can result in the loss of supination as well as pronation. Galeazzi fracture can also result when a person falls on the outstretched hand. It involves the fracture of the lower end of the radius and disruption of the distal radioulnar joint. This also results in the loss of pronation and supination.
Pronation and supination in the lower limb (foot and leg)
Pronation and supination movements in the foot are different from those in the upper limb. Pronation is the natural movement of the foot when it rolls inward. Thus, when walking, the foot tends to roll in a way that the weight of the body is more on the inner side of the foot. It is the normal side-to-side movement of the foot while running or walking. Some people may overpronate their feet while walking. During overpronation, with each step, the ankle rolls too far downward and inward. This makes the big and second toes do all the push-off and the feet twist more with each step. It can put a lot of strain on these toes besides making the feet unstable. It is commonly seen in people with a condition called the flat foot.
Supination refers to the rolling movement of the foot in which most of the weight of the body is transferred to the outer edge of the foot. This can result in excessive strain on the outer two toes and the outer edge of the foot. It is generally seen in people with highly arched feet.
Thus, there should be neutral pronation during movement. Excess or under pronation can result in various foot issues. To know the foot alignment and walking pattern (gait), one can consult a podiatrist or an orthopedic. They can also help choose the right kind of shoes to use during walking or running to avoid foot injuries.
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Chan CW, Rudins A. Foot Biomechanics During Walking and Running. Mayo Clin Proc. May 1994;69: 448-461. https://www.mayoclinicproceedings.org/article/S0025-6196(12)61642-5/pdf