Humerus adduction

To prevent impingement, the lower end of the humerus has two fossae, one at the front and one at the back. This gives the human elbow a range of 0 -142° of flexion extension with 5 of further passive flexion. About 9 of abduction and adduction exist in the ulno-humeral joint. This range of movement is essential to complete the full arc of pronation and supination. 

The capsule of the glenohumeral joint is loose and pleated. The ligaments, which are merely thickenings in the capsule, provide little support. The major support of the humerus into the fossa is provided by the rotator cuff muscles, which hold the head into the fossa. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. Abduction-adduction and axial and horizontal rotations are coupled in that angular motions are accompanied by translatory slides. The caudal slide of the humeral head with abduction confers increased freedom of motion on the supraspinatus tendon beneath the coracoacromial ligament. 

Range of motion should be checked actively and passively. Extension is minimal because of bony impingement. Flexion will be limited by the size of the biceps muscle. Besides the gross motions of flexion, extension, supination and pronation, the motion of the head of the radius must be evaluated as it glides on the lateral ulna. The motions of abduction and adduction of the ulna on the humerus should be evaluated. 

Adduction and abduction are accessory rocking motions of the upper part of the ulna on the trochlea of the humerus. Abduction is an accessory motion of pronation. Adduction is an accessory motion of supination. 

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