Fundamentals
Clare E. Milner in Functional Anatomy for Sport and Exercise, 2019
Bones have many different landmarks or features at and around the joints. Bony landmarks can be divided into articulating and non-articulating surfaces. Articulating surfaces are smooth cartilage-covered parts of bone that are part of the joints. Non-articulating surfaces are located at various sites on the bone where muscles, tendons, and ligaments attach. A head is an articulating surface that is rounded like a ball. The head of the humerus and the head of the femur are part of ball and socket joints at the shoulder (see shoulder complex – bones) and hip (see hip – bones) respectively. A condyle is a large articulating knob that is part of a compound joint. Examples are the femoral condyles at the knee (see knee – bones). A facet is a flat or shallow articular surface found at a gliding or sliding joint (see joint classification). The facets of the superior and inferior articular processes of the vertebrae are good examples (see vertebral structure).
The shoulder
David Silver in Silver's Joint and Soft Tissue Injection, 2018
The glenohumeral joint consists of the head of the humerus articulating with the glenoid fossa of the scapula. This shallow joint space is no more than 1.5 inches (3.8 cm) in length. The joint is held together by a rather loosely-applied voluminous capsule of fibrous tissue, which is considerably strengthened by the three tendons of the rotator cuff that blend with it anteriorly, posteriorly and superiorly, respectively, from the subscapularis, the infraspinatus together with teres minor, and the supraspinatus. The long head of the biceps tendon arises on the superior glenoid tubercle within the capsule of the joint and becomes covered by its own synovial sheath as it lies superiorly in the capsule. It leaves the joint space through an opening in the capsule, passing over the bicipital groove, which lies on the anterolateral surface of the head of the humerus, to join the short head of the biceps muscle anteriorly over the upper arm.
Upper Limb
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno in Understanding Human Anatomy and Pathology, 2018
The proximal portion of the humerus includes several gross features: head of the humerus, anatomical neck of the humerus, surgical neck of the humerus; processes for muscle attachment such as the greater tubercle of the humerus, lesser tubercle of the humerus, and deltoid tuberosity; and grooves for passage of tendons and vessels such as the humeral intertubercular sulcus (bicipital groove), and radial groove (Plate 4.7). As their names indicate, the anatomical neck is the one that can be more easily seen in gross observation of dry bones, surrounding the articular surface, while the surgical neck is the one most at risk of fracture. The articulation between the head of the humerus and the glenoid cavity of the scapula is called the glenohumeral joint or shoulder joint. The glenohumeral ligaments connecting the humerus and scapula strengthen the anterior wall of the capsule of the shoulder joint. The shoulder joint allows the humerus to be highly mobile: It can be flexed, extended, adducted, abducted, medially (internally) rotated, and externally (laterally) rotated (see Box 4.3).
Longitudinal assessments of strength and dynamic balance from pre-injury baseline to 3 and 4 months after labrum repairs in collegiate athletes
Published in Physiotherapy Theory and Practice, 2022
Ling Li, Brenna K. McGuinness, Jacob S. Layer, Yu Song, Megan A. Jensen, Boyi Dai
Sports-related labrum tears are associated with the high-risk repetitive motion and excessive contact force to the shoulder in sports. For example, the most common type (i.e. superior labrum tear and biceps tendon stripping) of SLAP tears is likely caused by repetitive overhead motion (Modarresi, Motamedi, and Jude, 2011). A mechanism of this injury is an abducted and externally rotated shoulder at a high velocity with a strongly activated biceps muscle, which often occurs in baseball pitching, tennis stroking, and volleyball spiking (Modarresi, Motamedi, and Jude, 2011). One frequent non-SLAP tear is the Bankart lesions, mostly occurring as anteroinferior tears of glenoid labrum due to anterior glenohumeral dislocation (McCarty, Ritchie, Gill, and McFarland, 2004). The anterior dislocation likely results from excessive external rotation and abduction of the shoulder, which forces the humerus out of the glenoid socket, damaging anterior structures in the process (Cutts, Prempeh, and Drew, 2009). As such, contact sports and collision sports such as American football and wrestling have an increased risk of anterior glenohumeral dislocations and Bankart lesions (Cho, Hwang, and Rhee, 2006; Mazzocca et al., 2005).
Understanding individuals’ perspectives and experiences of recovery following a proximal humerus fracture: an interpretive description
Published in Disability and Rehabilitation, 2022
Azar Varahra, Joy C. MacDermid, Mike Szekeres, David Walton, Kenneth J. Faber
Proximal humerus fractures (PHFs) are increasing in incidence, particularly in older adults, and optimizing their outcomes can be challenging [1–5]. Fracture of the proximal part of the humerus is one of the most common fragility fractures and, like other fragility fractures, is most prevalent with increasing age [5]. After sustaining PHF, individuals report considerable difficulty in undertaking daily activities involving the shoulder (i.e., personal hygiene, household chores, carrying items) [4,6,7]. PHF is a severe upper limb injury because it affects individuals’ ability to do their everyday activities [7]. Loss of upper limb function can be very disabling and potentially influence the quality of life of a previously independent person [8,9]. It is also well documented that a significant proportion of patients sustaining PHF continue to experience disability at one year and even up to 18 months [3,5,6,10]. Price et al. (2005) reported that many patients with PHF never fully recover their pre-fracture functional independence [5]. Hence, frustration and disappointment can be quite high when expectations are unfulfilled, symptoms persist, and individuals depend on others to do things they had previously done by themselves.
Mechanisms of Modulation of Automatic Scapulothoracic Muscle Contraction Timings
Published in Journal of Motor Behavior, 2021
Samuele Contemori, Roberto Panichi, Andrea Biscarini
One possibility is related to the line of force of the MD. The downward scapular rotation increases the angle between the force of gravity and the forces expressed by the structures that are responsible for the vertical stability of the humeral head (Neumann, 2010). If this angle is enhanced the summation of the two force vectors results in the decrement of the compressive force, which is responsible for the locking of the humeral head against the glenoid fossa of the scapula. In this configuration, the MD could give a contribution to the humeral head stability by its upward-medial oriented line of force. This might have induced a slight preactivation of the muscle, which may increase the responsiveness of the muscle to the following motor command (Contemori et al., 2020; Wood et al., 2015), thus facilitating the discrimination of the contraction onset time (Contemori et al., 2020). Another possibility is that the downward scapular rotation led to a shortening of the pre-abduction length of the MD, due to the movement of the acroimal origin of the muscle to its humeral insertion. This might result in a mechanical disadvantage of the muscle to initiate the abduction movement and, as a consequence, sharpen the initial response of the muscle, thus facilitating the discrimination of its timing of contraction.