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The elbow joint (Figures 22-1, 22-2, 22-3, 22-4, 22-5, and 22-6) is a compound synovial joint and consists of the radiohumeral (radiocapetellar), ulnohumeral (trochlear), and proximal radioulnar articulations. The movements of elbow flexion and extension occur at the ulnohumeral joint and range between 150 and 160 degrees, with between 0 and 10 degrees of hyperextension. The main flexor muscles are biceps brachii and brachialis, whereas the main extensor muscle is triceps. The movements of supination and pronation occur at the proximal radioulnar joint and the radiohumeral joint. Biceps brachii muscle and supinator muscles are the primary supinators, whereas the pronator teres is the primary pronator. The ulnar or medial collateral ligament is the major stabilizer of the elbow joint during the throwing motion. The timing of appearance of secondary ossification centers around the elbow is listed in Table 22-1. All fuse to form a singe epiphysis between 14 and 17 years of age. The distal humeral physis contributes approximately 20% to final length of humerus.
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