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Musculoskeletal system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The shoulder joint is a synovial ball-and-socket joint formed between the head of the humerus and the glenoid cavity of the scapula (Fig. 3.18a). The glenoid cavity is shallow, which makes the joint unstable. It has a wide range of movements and relies on muscle support for stability. The joint capsule is lax to permit the wide range of movements available at the joint. It attaches close to the margin of the head of humerus, except inferiorly where it attaches 2–3 cm distally. The capsule is strengthened by four muscles, subscapularis, supraspinatus, infraspinatus and teres minor, which are known collectively as the rotator cuff. Subscapularis originates on the anterior aspect of the scapula and inserts into the lesser tuberosity of the humerus. Supraspinatus originates from the supraspinous fossa of the scapula and inserts into the superior aspect of the greater tuberosity of the humerus. Infraspinatus originates from the infraspinous fossa on the scapula and inserts into the middle portion of the greater tuberosity. Teres minor originates from the upper two-thirds of the axillary border of the scapula (posterior surface) and inserts into the inferior aspect of the greater tuberosity.
Repetitive TasksRisk Assessment and Task Design
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
The shoulder joint is a kind of ball and socket joint but the ball part, the head of the humerus or upper arm bone, represents only a third of the surface of a sphere when it engages the socket. The socket (the glenoid cavity of the scapula, or shoulder blade) is correspondingly shallow. The head of the humerus has to be held in place by tonic muscle activity. This explains why the shoulder joint is so easily dislocated. This can be contrasted with the much more stable hip joint where over 50% of the femoral head is enclosed by the acetabulum.
Work-Related Ill Health
Published in Céline McKeown, Office Ergonomics and Human Factors, 2018
Sufferers from frozen shoulder start by experiencing a gradual onset of stiffness, accompanied by shoulder pain that is more prominent at night. Ultimately, they experience significant restriction in all shoulder movements. This results from the inflammation in or degeneration of the shoulder joint tissue. Overhead work that is repeated or sustained for extended periods is believed to contribute to this condition. It can also occur spontaneously without any identifiable provocation.
Accuracy and reliability of a method for measuring three-dimensional articular motions of the shoulder complex during swimming
Published in Sports Biomechanics, 2022
The shoulder joint connects the arm and torso. It is a complex structure consisting of the humerus, scapula, and clavicle, which are joined by the glenohumeral, acromioclavicular, and sternoclavicular joints. The motion of the glenohumeral joint and the ratio of glenohumeral motion to scapulothoracic motion during movement of the arm are frequently described in studies of the mechanism of injury and when evaluating performance in overhead sports (Kibler, 1998; Konda, Yanai, & Sakurai, 2015; Myers, Laudner, Pasquale, Bradley, & Lephart, 2005). There have been few studies on the three-dimensional motion of the glenohumeral joint and scapulothoracic articulation in swimming or other aquatic sports. The main reason may be the technical difficulties involved. Optical camera systems are often used to measure the kinematics of various body segments during swimming (Ceseracciu et al., 2011; Monnet, Samson, Bernard, David, & Lacouture, 2014; Yanai & Hay, 2000). However, it is difficult to investigate the movements of the glenohumeral joint and scapulothoracic articulation using these methods because the scapula slides freely underneath the skin surface and is hard to observe with optical systems.