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The term goniometry derives from two Greek words, γωνία 'angle' and μέτρον 'measure'. [1] The protractor is a commonly used type in the fields of mechanics, engineering, and geometry. The first known description of a goniometer, based on the astrolabe , was by Gemma Frisius in 1538.
These three muscles act as flexors at the elbow joint. [5] The extensor carpi radialis brevis and longus are both weak flexors at the elbow joint. Brevis moves the arm from ulnar abduction to its mid-position and flexes dorsally. Longus is a weak pronator in the flexed arm and a supinator in the outstretched arm.
The radius can thus glide on the capitulum during elbow flexion-extension while simultaneously rotate about its own main axis during supination-pronation. [2] Between the capitulum and the trochlea of the humerus is the capitulotrochlear groove. A semi-lunar surface around the circumference of head is shaped to articulate continuously with this ...
The brachioradialis is a stronger elbow flexor when the forearm is in a midposition between supination and pronation at the radioulnar joint. When pronated, the brachioradialis is more active during elbow flexion since the biceps brachii is in a mechanical disadvantage.
Additionally, as the forearm moves from pronation to supination, the interosseous membrane fibers change from a relaxed state, to a tense state in the neutral position. They once again become relaxed as the forearm enters pronation. The interosseous membrane is composed of five ligaments:
Supinator always acts together with biceps, except when the elbow joint is extended. [7] It is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading. [8] Supination strength decreases by 64% if supinator is disabled by, for example, injury. [9]
The quadrate ligament reinforces the inferior part of the capsule of the elbow joint [1] and contributes to joint stability by securing the proximal radius against the radial notch and by restricting excessive supination (10–20° restriction) and, to a lesser degree, pronation (5–8°).
The elbow is the region between the upper arm and the forearm that surrounds the elbow joint. [1] The elbow includes prominent landmarks such as the olecranon , the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the medial epicondyles of the humerus .