Anatomy and biomechanics of the acromioclavicular and sternoclavicular joints

Kevin J Renfree1, Thomas W Wright

  • 1Department of Orthopaedic Surgery, Mayo Clinic Hospital, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA. renfree.kevin@mayo.edu

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The muscles surrounding the shoulder girdle, including the clavicle and scapula, primarily stabilize the scapula. This stable base allows other muscles to move the humerus effectively. Scapular movements often mirror those of the humerus and extend its range of motion. For instance, raising the arm above the head would not be feasible without simultaneous upward rotation of the scapula.
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Functional Classification of Joints
The functional classification of joints is determined by the amount of mobility between the adjacent bones. Joints are functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, a freely moveable joint. Fibrous and cartilaginous joints can be functionally classified as either synarthroses  or amphiarthroses, whereas all synovial joints are classified as diarthroses.
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