• Protraction of the scapula For example, if the shoulder is abducted to 90 degrees, only about 60 degrees of that motion occurs from GH abduction; the additional 30 degrees or so is achieved through upward rotation of the scapula. Use the images below for reference. Two Ways to Help Prevent Shoulder Impingement Her medical history includes a diagnosis of early-stage breast cancer in the right breast 6 months ago. Sternum Chapter 4 • Sternoclavicular Ligament: Contains anterior and posterior fibers that firmly join the clavicle to the manubrium, • Joint Capsule: Surrounds the entire SC joint; is reinforced by the anterior and posterior SC joint ligaments, • Interclavicular Ligament: Spans the jugular notch, connecting the superior medial aspects of the clavicles, • Costoclavicular Ligament: Firmly attaches the clavicle to the costal cartilage of the first rib and limits the extremes of all clavicular motion except depression, • Articular Disc: Acts as a shock absorber between the clavicle and the sternum; helps improve joint congruency. The body or middle portion of the sternum serves as the anterior attachment for ribs 2 through 7. The slightly concave anterior aspect of the bone is called the subscapular fossa, which allows the scapula to glide smoothly along the convex posterior rib cage. Symptoms of SLAP lesions often involve pain with overhead activities and “clicking” or “popping” of the shoulder. ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-39. At the same time, it must be mobile enough for these actions to occur. This site uses cookies to provide, maintain and improve your experience. The greater and lesser tubercles are divided by the intertubercular groove, often called the bicipital groove because it houses the tendon of the long head of the biceps. In this episode of eOrthopodTV, orthopaedic surgeon Randale C. Sechrest, MD narrates an animated tutorial on the basic anatomy of the shoulder. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-19, (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-25. With the shoulder in roughly 90 degrees of abduction, movement of the humerus toward the midline in the horizontal plane is considered horizontal adduction. Proximal attachments of muscles are shown in red, distal attachments in gray. Objective: Movements of the human shoulder represent the result of a complex dynamic interplay of structural bony anatomy and biomechanics, static ligamentous and tendinous restraints, and dynamic muscle forces. The relatively large amount of GH joint instability produced by relatively small alterations in the posture of the scapula is good evidence that proper posture of the scapula contributes significantly to the stability of the GH joint. In essence, this joint links the motion of the. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-1.) The acromion process is a wide, flattened projection of bone from the most superior-lateral aspect of the scapula. A superior view of the right clavicle articulating with the sternum and the acromion. This tendon helps provide anterior stability because it acts as a partial extension of the glenoid labrum.  Strong force-dissipating structures such as the SC disk and the costoclavicular ligament minimize articular stresses and also prevent excessive intra- articular motion that might lead to … Muscles of the shoulder. • Interclavicular Ligament: Spans the jugular notch, connecting the superior medial aspects of the clavicles • Describe the location and primary function of the ligaments that support the joints of the shoulder complex. Summary All four joints must properly interact for normal shoulder motion to occur. The sternoclavicular (SC) joint is created by the articulation of the medial aspect of the clavicle with the sternum (Figure 4-6). The human shoulder is a complex structure that must be stable enough to support the actions of the arm and hands like pulling, lifting, and pushing object. This bony conformation, in conjunction with the highly mobile scapula, allows for abundant motion in all three planes but does not promote a high degree of stability. Physical therapy for these conditions usually involves regaining strength and range of motion and participating in a muscle stabilization program that fits the needs of the patient. Commonly called the shoulder blade, the scapula is a highly mobile, triangular bone that rests on the posterior side of the thorax (Figure 4-4). • Downward rotation and retraction of the scapula The shoulder’s main motions are flexion, extension, abduction, adduction, internal rotation, and external rotation. Ideal posture of the scapula positions the glenoid fossa so that it is tilted about 5 degrees upward (Figure 4-17, A). Innervation of the Shoulder Complex Abduction and Adduction The shoulder complex functions through the interactions of which four joints? The limited range of motion experienced in a neutral or internally rotated position is caused by the greater tuberosity impinging against the acromion process. The glenohumeral (GH) joint, which links the humerus and scapula, has greater mobility than any other joint in the body. Scapular elevation involves the scapula sliding superiorly on the thorax (e.g., shrugging the shoulders). The glenoid labrum is a fibrocartilaginous ring of connective tissue that increases the stability of the glenohumeral joint. Recall that the head of the humerus is a large, rounded hemisphere, and that the glenoid fossa is relatively flat. 7–1). The static locking mechanism of the glenohumeral joint. Often seen with baseball and football players who are professional overhead athletes … For organizational purposes, this text divides these muscles into two categories: (1) Muscles of the shoulder girdle, and (2) muscles of the GH joint. She reports feelings of tightness over the anterior chest region when she raises her right arm. = 60 degrees of scapulothoracic joint upward rotation Muscle and Joint Interaction To achieve full range of motion during abduction, the prominent greater tuberosity must be positioned to clear the undersurface of the acromion; this can be accomplished by externally rotating the shoulder or performing abduction in the scapular plane. The labrum serves to deepen the socket of the GH joint, nearly doubling the functional depth of the glenoid fossa. Muscle and Joint Interaction Horizontal abduction and horizontal adduction are commonly used terms to describe special motions of the shoulder and are described in the following section. The labrum performs this important function in two ways. • Clavicular elevation and posterior rotation, Two Ways to Help Prevent Shoulder Impingement. Equally important, these motions allow the scapula to maintain firm contact with the posterior thorax. The glenohumeral (GH) joint is a true synovial ball-and-socket style diarthrodial joint that is responsible for connecting the upper extremity to the trunk. Clavicle The humerus is a long bone that forms the articulations of the glenohumeral joint proximally (with the scapula), and the humeral ulnar joint and humeral radial joint • Horizontal adduction of the humerus This chapter provides an overview of the kinesiology of the four joints of the shoulder complex and the important muscular synergies that support proper function of the shoulder (Figure 4-1). SHOULDER ANATOMY There are four main joints within the shoulder complex, and an even greater number of muscles involved in moving both the humerus (upper arm) and scapula (shoulder blade). Ideally, the scapula is positioned on a rib cage that’s mounted on a fully functioning, symmetrical thoracic spine. Susan Sorenson is a 42-year-old dental hygienist who presents to the clinic with a chief complaint of right shoulder pain. This series of joints works together to provide large ranges of motion to the upper extremity in all three planes. Cite the proximal and distal attachments, actions, and innervation of the muscles of the shoulder complex. • Describe the interaction between the internal and external rotators of the shoulder during a throwing motion. Internal and external rotation of the GH joint occurs in the horizontal plane about a vertical (longitudinal) axis of rotation (see Figure 4-13). 2011;46(4):349-357. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-17.)   •   Privacy Policy Figure 4-10 illustrates the supporting structures of the AC joint. When the arm is at rest, near the side of the body, the head of the humerus is held flush against the glenoid fossa, in part by the static locking mechanism of the glenohumeral (GH) joint. • Describe the planes of motion and axes of rotation for the primary motions of the shoulder. Figure 4-17 The static locking mechanism of the glenohumeral joint. However, the competing mobility and stability demands on the shoulder girdle and the intricate structural and functional design make the shoulder complex highly susceptible to dysfunction and instability. A, Elevation and depression. Kinematics The muscles of the shoulder complex, therefore, must work in a highly coordinated fashion. Interaction Among the Joints of the Shoulder Complex Not only does the humeral head lose its ledge on which to rest, but the direction of the upward forces created by the superior capsular ligaments is changed, reducing the overall potential of these structures to produce a passive compression force (CF). Figure 4-18 The brachial plexus. Figure 4-6 An anterior view of the sternoclavicular joints with the capsule and some of the ligaments removed on the left side.  Objectives As the shoulder is abducted, the coracoclavicular ligament becomes taut and spins the clavicle posteriorly. The radial (spiral) groove runs obliquely across the posterior surface of the humerus. Although the components of the shoulder complex constitute half of the mass of the entire upper limb,1 they are connected to the axial skeleton by a single joint, the sternoclavicular (SC) joint. For that reason, and because of the dexterity of the shoulder joint itself, the musculature of the shoulder is complex, ranging from massive prime mover muscles to finer stabilizer and fixator muscles. Explain the force-couple that occurs to produce upward rotation of the scapula. • Describe the muscular interactions involved with active shoulder abduction. The osseous segments of the shoulder complex are the clavicle, scapula, and humerus (Fig. The radial nerve follows this groove and helps define the distal attachment for the lateral and medial heads of the triceps. • Explain how the shoulder depressor muscles can be used to elevate the thorax. Downward rotation occurs as the scapula returns from an upwardly rotated position to its resting position. Elevation and depression of the SC joint is a near-frontal plane movement about a near–anterior-posterior axis of rotation, allowing roughly 45 degrees of clavicular elevation and 10 degrees of depression. Log In or Register to continue The articular structures of the shoulder complex, in particular the GH Joint, are designed primarily for mobility, allowing us to move and position the hand through a wide range of space, allowing the greatest range of motion of any joint in the body. The shoulder joint is formed by the articulation of the head of the humerus with theglenoid cavity(or fossa) of the scapula. Not only does the humeral head lose its ledge on which to rest, but the direction of the upward forces created by the superior capsular ligaments is changed, reducing the overall potential of these structures to produce a passive compression force (CF). These three segments are joined by three interdependent linkages: the sternoclavicular joint, the acromioclavicular (AC) joint, and the glenohumeral joint. force-couple The high degree of stability provided by this thick ligamentous network explains, in part, why fractures of the clavicle occur more frequently than dislocations of the SC joint. ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-3. Because strong forces are frequently transferred across the AC joint, several important stabilizing structures are required to maintain its structural integrity. … It helps limit the extremes of external rotation, flexion, and extension, as well as inferior displacement of the humeral head (see Figure 4-12). It must be understood, however, that movement of the entire shoulder is the result of movement in each of its four joints. downward rotation Along with the acromion, the coracoacromial ligament completes the coracoacromial arch—a functional “roof” that protects the head of the humerus. • Describe the interaction between the internal and external rotators of the shoulder during a throwing motion. This chapter provides an overview of the kinesiology of the four joints of the shoulder complex and the important muscular synergies that support proper function of the shoulder (Figure 4-1). ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-30.). Discuss basic movement patterns of the shoulder complex … Interaction Among the Joints of the Shoulder Complex Figure 4-3 A superior view of the right clavicle articulating with the sternum and the acromion. The head of the humerus is much larger than the glenoid fossa, giving the joint a wide range of movement at the cost of inherent instability. Downward rotation occurs as the scapula returns from an upwardly rotated position to its resting position. However, if the shoulder is externally rotated, the greater tuberosity is positioned posterior to the coracoacromial arch, thereby avoiding full impact with the acromion. https://fadavispt.mhmedical.com/content.aspx?bookid=1862§ionid=136085052. The scapulothoracic joint is not a “true” joint in the traditional sense. Motions of the right scapula against the posterior-lateral thorax. Description Anterior view of the left shoulder and acromioclavicular joints, and proper scapular ligaments. The medial or sternal end of the clavicle articulates with the manubrium of the sternum, forming the sternoclavicular joint. It helps limit the extremes of external rotation, flexion, and extension, as well as inferior displacement of the humeral head (see Figure 4-12). This motion involves the typical scapulohumeral rhythm: a 2 : 1 ratio of glenohumeral flexion and scapulothoracic upward rotation. • Describe the location and primary function of the ligaments that support the joints of the shoulder complex. • Costoclavicular Ligament: Firmly attaches the clavicle to the costal cartilage of the first rib and limits the extremes of all clavicular motion except depression Much of the stability in the shoulder complex is … "The Shoulder Complex." • Depression and retraction of the clavicle Nerve roots C5 and C6 form the upper trunk, C7 forms the middle trunk, and C8 and T1 form the lower trunk. Study Questions The right glenohumeral joint showing the conventional osteokinematic motions of the humerus. • Joint Capsule: Surrounds the entire SC joint; is reinforced by the anterior and posterior SC joint ligaments • Protraction of the clavicle For that reason, and because of the dexterity of the shoulder joint itself, the musculature of the shoulder is complex, ranging from massive prime mover muscles to finer stabilizer and fixator muscles.

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