Anconeus Muscle

The posterior compartment includes the triceps and the anconeus muscles. The triceps is a large muscle made up of three heads-medial, lateral and long-from which it derives its name. The muscle bellies converge into a single thick tendon which attaches on the posterior aspect of the olecranon process. To increase the strength of extension of the elbow joint, the triceps tendon does not insert on the tip of the olecranon, but approximately 1 cm distal... 

Extension of the elbow from the anatomic position is limited (5 to 10 degrees) by contact of the olecranon process with the fossa, tension in the anterior ligament, and resistance of anterior muscles. The triceps brachii is the only significant elbow muscle that functions in extension. There is some minor contribution by the anconeus. Because most elbow extension is accomplished by gravity, the triceps functions primarily against resistance. 

Martinoli C, Bianchi S, Prato N et al (2003) US of the shoulder non-rotator cuff disorders. RadioGraphics 23 381-401 Martinoli C, Bianchi S, Gotten A (2005) Imaging of rock climbing injuries. Semin Musculoskelet Radiol 9 334-345 Masear VR, Hill JJ, Cohen SM (1988) Ulnar compression neuropathy secondary to the anconeus epitrochlearis muscle. J Hand Surg [Am] 13 720-724... 

The anconeus epitrochlearis is a small accessory muscle (prevalence ranging from 1% to 34%) that forms the roof of the cubital tunnel, replacing the Osborne retinaculum and joins the posterior aspect of the medial epicondyle with the medial aspect of the olecranon.. This muscle is often bilateral and can cause ulnar neuropathy by occupying space within the cubital tunnel and decreasing its free volume during full elbow flexion. Somewhat equivalent to the anconeus epitrochlearis, an anomalous myotendinous junction of the triceps may also be prominent over the posteromedial side of the cubital tunnel (see Sect. 8.5.4.S). 

Fig. 8.57a-d. Cubital tunnel syndrome in a patient with anconeus epitrochlearis muscle, a Short-axis and b long-axis 12-5 MHz US images of the cubital tunnel reveal the anconeus epitrochlearis muscle (straight arrows) that lies between the medial epicondyle (ME) and the olecranon (0) in close relation with a swollen ulnar nerve (curved arrow). Correlative transverse c Tlw SE and d fat-suppressed T2w SE MR images demonstrate the aberrant muscle (straight arrows) within the cubital tunnel. In d, the ulnar nerve (curved arrow) appears markedly hyperintense as a result of compression neuropathy. ME, medial epicondyle 0, olecranon... 

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