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Anatomy of the Shoulder Muscles Explained Anatomy of the shoulder. 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. Sternoclavicular, scapulothoracic, acromioclavicular, and glenohumeral. Joint Structure & Function: A Comprehensive Analysis, 6e Levangie PK, Norkin CC, Lewek MD. Depression occurs when the scapula slides inferiorly on the thorax (Figure 4-9, A; e.g., returning shrugged shoulders to a resting position; depressing the entire shoulder, as occurs when pushing up from a sitting position). • Rotator Cuff: A group of four muscles including the supraspinatus, infraspinatus, subscapularis, and teres minor. She had a lumpectomy with sentinel node biopsy, followed by radiation treatments for 5 weeks. = 60 degrees of scapulothoracic joint upward rotation The shoulder complex, composed of the clavicle, scapula, and humerus, is an intricately designed combination of three joints that links the upper extremity to the thorax. The static locking mechanism helps provide stability to this loose-fitting joint. The intricacy of the neuromotor components controlling shoulder motion and athletic. Shoulder internal rotation often occurs naturally with pronation, whereas shoulder external rotation naturally occurs with supination. Most often, this type of injury results in a SLAP lesion (Superior Labrum from Anterior to Posterior), which involves the superior aspect of the labrum. During shoulder movements such as lifting, certain muscle groups help to move the shoulder, while other muscle groups help to stabilize the shoulder complex. Depression occurs when the scapula slides inferiorly on the thorax (Figure 4-9, A; e.g., returning shrugged shoulders to a resting position; depressing the entire shoulder, as occurs when pushing up from a sitting position). The humeral head is nearly one half of a full sphere that articulates with the glenoid fossa forming the glenohumeral joint. The scapular plane is about 35 degrees anterior to the frontal plane (Figure 4-16, B). The clavicle, commonly called the collarbone, is an S-shaped bone that acts like a mechanical rod that links the scapula to the sternum (Figure 4-3). • Sternoclavicular The glenoid fossa is the slightly concave, oval-shaped surface that accepts the head of the humerus, composing the glenohumeral joint. • Describe the planes of motion and axes of rotation for the primary motions of the shoulder. Normally, the GH joint allows approximately 120 degrees of abduction; the full 180 degrees of shoulder abduction normally occurs by combining 60 degrees of scapular upward rotation with the abduction of the GH joint. Most often, this type of injury results in a SLAP lesion (Superior Labrum from Anterior to Posterior), which involves the superior aspect of the labrum. This freedom of movement makes the shoulder … Scapulothoracic motion is an integral part of nearly every shoulder movement. Clavicle Kinematics The shoulder’s main motions are flexion, extension, abduction, adduction, internal rotation, and external rotation. Second, approximately 50% of the fibers of the long head of the biceps tendon are direct extensions of the superior glenoid labrum. This will improve shoulder position and posture over time, which will ultimately lead to better function of the shoulder complex and can improve total kinetic chain movement. Scapular plane abduction is more natural than abduction in the pure frontal plane. 2. The labrum serves to deepen the socket of the GH joint, nearly doubling the functional depth of the glenoid fossa. Figure 4-14 A, Proper arthrokinematics of the glenohumeral (GH) joint during abduction involving a superior roll and inferior slide of the humeral head. Rather, muscles work in teams to produce highly coordinated movements that are expressed over multiple joints. 2019 Jan;39(1):e32-e38. Horizontal abduction and horizontal adduction are commonly used terms to describe special motions of the shoulder and are described in the following section. • Cite the normal ranges of motion for shoulder flexion and extension, abduction and adduction, and internal and external rotation. Abduction and Adduction All of the nerves that travel down the arm pass through the axilla (the armpit) just under the shoulder joint and are known as the Brachial Plexus before dividing into the individual nerves.These nerves carry the signals from the brain to the muscles that move the arm. The next steps in treatment or work-up can then … This gives rise to the alternate name for the shoulder joint – the glenohumeral joint. Four muscles and their attached tendons make up the rotator cuff. Protraction and retraction of the SC joint occur in the horizontal plane about a vertical axis of rotation, allowing about 15 to 30 degrees of clavicular motion in either direction. The scapular spine divides the posterior aspect of the scapula into the supraspinatous fossa (above) and the infraspinatous fossa (below). The larger, more rounded lateral projection of bone is the greater tubercle. The arthrokinematics of abduction involves the convex head of the humerus rolling superiorly while simultaneously sliding inferiorly (Figure 4-14, A). 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. All four joints must properly interact for normal shoulder motion to occur. • Horizontal adduction of the humerus Patients with Bankart lesions typically complain of significant shoulder instability, or feel as if the shoulder could “pop out” during various activities. Even with the humerus in full external rotation, complete abduction of the shoulder may result in impingement if performed in the true frontal plane (Figure 4-16, A). Kinematics This joint provides the only direct bony attachment of the upper extremity to the axial skeleton—accordingly, the joint must be stable while also allowing extensive mobility. Muscle and Joint Interaction The muscles of the shoulder complex, therefore, must work in a highly coordinated fashion. 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. 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. It is interesting to note that with optimal posture of the scapula, little GH joint muscle activity is required for stability at rest. Only gold members can continue reading. • Clavicular elevation and posterior rotation, Two Ways to Help Prevent Shoulder Impingement. The shoulder is a complex joint with many muscles that control the shoulder’s wide range of motion. It is interesting to note that with optimal posture of the scapula, little GH joint muscle activity is required for stability at rest. 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. She localizes the pain primarily at the lateral proximal humerus (C5 dermatome region) but also reports pain in the upper trapezius. The cords eventually branch into nerves that primarily innervate muscles of the upper extremity. F. during open-chain abduction of the shoulder, the arthrokinematic roll and slide occur in the same direction. downward rotation Horizontal Abduction and Horizontal Adduction • Identify the bones and primary bony features relevant to the shoulder complex. Recall that the glenoid fossa is relatively flat and shallow, whereas the humeral head is large and round, making the anatomy of this joint more like a golf ball sitting on a quarter than like a ball-and-socket joint. Sternoclavicular Joint The acromion forms a functional “roof” over the humeral head to help protect the delicate structures within that area. In this episode of eOrthopodTV, orthopaedic surgeon Randale C. Sechrest, MD narrates an animated tutorial on the basic anatomy of the shoulder. = 180 degrees of shoulder abduction • Describe the interaction between the internal and external rotators of the shoulder during a throwing motion. Sternum Movement of all of these components must occur for the arm to achieve 180° of humeral elevation. The medial or sternal end of the clavicle articulates with the manubrium of the sternum, forming the sternoclavicular joint. 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). Rather, muscles work in teams to produce highly coordinated movements that are expressed over multiple joints. General Features It is essential for these normal relationships to be defined as a basis for understanding pathology. This means that for every 2 degrees of GH abduction, the scapula must simultaneously upwardly rotate roughly 1 degree. The cooperative nature of the shoulder musculature increases the versatility, control, and range of active movements available to the upper extremity. The medial or sternal end of the clavicle articulates with the manubrium of the sternum, forming the sternoclavicular joint. As a result, muscle forces serve as a primary mechanism for securing the shoulder girdle to the thorax and providing a stable base of support for upper extremity movements. Because of the nature of this functional relationship among the shoulder muscles, paralysis. Elevation and Depression Furthermore, motion at the scapulothoracic joint is dependent on the combined movements of the AC and SC joints. • Describe the muscular interactions involved with active shoulder abduction. Kibler WB. The sternum, often called the breast bone, is located at the midpoint of the anterior thorax and is composed of the manubrium, body, and xiphoid process (Figure 4-2). SHOULDER COMPLEX ANATOMY Osseous Elements The shoulder complex includes the articulations of the humerus, the clavicle, the scapula, and the posterior surface of the ribs. Along with the acromion, the coracoacromial ligament completes the coracoacromial arch—a functional “roof” that protects the head of the humerus. Bankart lesions, on the other hand, involve tears to the anterior-inferior portion of the glenoid labrum. Supporting Structures of the Acromioclavicular Joint The axes of rotation are color coded with the associated planes of motion. The shoulder complex plays an integral role in performing an athletic skill involving the upper. Scapular movements include: Anterior/posterior tilting, upward/downward rotation. Nerve roots C5 and C6 form the upper trunk, C7 forms the middle trunk, and C8 and T1 form the lower trunk. the shoulder complex is equipped with more external rotor than internal rotator muscles. 7–1). • Describe the planes of motion and axes of rotation for the primary motions of the shoulder. Much of the stability in the shoulder complex is … Clinically, the inferior angle is important in helping track scapular motion. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-1.) ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-30.). Acromioclavicular and Sternoclavicular Joint Interaction Within the Scapulohumeral Rhythm Regardless of the type of lesion, surgery may be indicated if the tear of the labrum is large—or if conservative methods of treatment are unsuccessful. This site uses cookies to provide, maintain and improve your experience. • Upward rotation of the scapula The larger, more rounded lateral projection of bone is the greater tubercle. Active internal and external rotation at the shoulder is functionally linked with active pronation and supination of the forearm. Discuss basic movement patterns of the shoulder complex … The entire upper extremity receives innervation primarily through the brachial plexus (Figure 4-18). Abduction involves the 2 : 1 ratio of glenohumeral abduction to scapular upward rotation—the scapulohumeral rhythm. Normal movement and posture of the scapulothoracic joint are essential to the normal function of the shoulder. Approximately 120 degrees of flexion and 45 degrees of extension are available to the GH joint. • Identify the primary muscles involved with dynamic stabilization of the glenohumeral joint. The distal humerus is discussed in the next chapter. Putting It All Together Her medical history includes a diagnosis of early-stage breast cancer in the right breast 6 months ago. Symptoms include pain and fatigue with elevating her arm and the inability to sleep on her right shoulder. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-38.) • Acromioclavicular Large forces that tax the biceps tendon can partially detach or tear the loosely attached superior labrum. Cite the proximal and distal attachments, actions, and innervation of the muscles of the shoulder complex. Equally important, these motions allow the scapula to maintain firm contact with the posterior thorax. The radial nerve follows this groove and helps define the distal attachment for the lateral and medial heads of the triceps. Without an inferior slide, the upward roll of the humerus will result in the humeral head jamming into the acromion. The right sternoclavicular joint showing the osteokinematic motions of the clavicle. Figure 4-15 Posterior view of the right shoulder complex after the arm has abducted 180 degrees. The right glenohumeral joint showing the conventional osteokinematic motions of the humerus. The superior capsular ligaments provide an upward force vector to counteract the downward force of gravity. Discuss basic movement patterns of the shoulder complex … Abduction involves the 2 : 1 ratio of glenohumeral abduction to scapular upward rotation—the scapulohumeral rhythm. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-3.) The lesser tubercle is a sharp, anterior projection of bone just below the humeral head. At the same time, it must be mobile enough for these actions to occur. This important concept is discussed further in a subsequent section. 2011;46(4):349-357. With the shoulder in roughly 90 degrees of abduction, movement of the humerus toward the midline in the horizontal plane is considered horizontal adduction. Internal and External Rotation Muscle and Joint Interaction All together they help hold your upper arm in place in the shoulder … To reduce the disproportion in surfaces, the glenoid fossa is deepened by a fibrocart… 8. 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. The scapular spine divides the posterior aspect of the scapula into the supraspinatous fossa (above) and the infraspinatous fossa (below). Proximal attachments of muscles are shown in red, distal attachments in gray. These three segments are joined by three interdependent linkages: the sternoclavicular joint, the acromioclavicular (AC) joint, and the glenohumeral joint. Structure and Function of the Shoulder Complex C, Upward and downward rotation. Downward rotation occurs as the scapula returns from an upwardly rotated position to its resting position. Clavicle The manubrium is the most superior portion of the sternum that articulates with the clavicle—forming the sternoclavicular joint. • Glenoid Labrum: A fibrocartilaginous ring that encircles the rim of the glenoid fossa. In essence, all movements of the shoulder girdle (i.e., the scapula and clavicle) originate at the SC joint. Movement away from the midline in the horizontal plane is considered horizontal abduction. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Google+ (Opens in new window) The axes of rotation are color coded with the associated planes of motion. 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. This conformation allows the clavicle to move in all three planes. Innervation of the Shoulder Complex 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. However, the shoulder complex relies on more than just the scapula for safe and efficient function. Anterior view of the right acromioclavicular joint, including many of the surrounding ligaments. static stability  Clinical insight This conformation allows the clavicle to move in all three planes. Motions at the scapulothoracic joint include elevation and depression, protraction and retraction, and upward and downward rotation (Figure 4-9). As illustrated in Figure 4-17, B, when the scapula becomes downwardly rotated, as commonly occurs after a stroke involving weakness or paralysis of the trapezius muscles, the static locking mechanism becomes ineffective. • Describe the location and primary function of the ligaments that support the joints of the shoulder complex. • Coracoclavicular Ligament: Composed of the conoid and trapezoid ligaments. The entire upper extremity receives innervation primarily through the brachial plexus (Figure 4-18). all 4 muscles help stabilize the humeral head within the glenoid fossa. Static Passive Locking Mechanism of the Glenohumeral Joint. Acromioclavicular Joint The shoulder has several other important structures: The rotator cuff is a collection of muscles and tendons that surround the shoulder, giving it support and allowing a wide range of … Joint Structure and Function: A Comprehensive Analysis, 5e. Log In or Register to continue Numerous structural and functional reasons explain why the labrum is so often involved with shoulder pathology. The clavicle rotates anteriorly, back to its rest position, as the shoulder is extended or adducted. This motion naturally occurs as an elevated upper extremity is lowered to one’s side. The radial (spiral) groove runs obliquely across the posterior surface of the humerus. 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). Proximal attachments of muscles are shown in red, distal attachments in gray. Motions include elevation and depression, protraction and retraction, and axial rotation (Figure 4-8). athletic patients. The contradictory requirements on the shoulder complex for both mobility and stability are met through active forces, or dynamic stabilization, a concept of which the shoulder complex is considered a classic example. Our study of the upper limb begins with the shoulder complex—a set of four articulations involving the sternum, clavicle, ribs, scapula, and humerus (Figure 4-1). ), (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby, Figure 5-38. Internal rotation results in the anterior surface of the humerus rotating medially, toward the midline, whereas external rotation results in the anterior surface of the humerus rotating laterally, away from the midline. Internal and external rotation of the GH joint occurs in the horizontal plane about a vertical (longitudinal) axis of rotation (see Figure 4-13). The muscles of the shoulder bridge the transitions from the torso into the head/neck area and into the upper extremities of the arms and hands. It helps limit the extremes of external rotation, flexion, and extension, as well as inferior displacement of the humeral head (see Figure 4-12). Figure 4-6 illustrates the supporting structures of the SC joint. 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 4-16 A side view of the right glenohumeral joint comparing abduction of the humerus in the (A) true frontal plane and in the (B) scapular plane. Explain the force-couple that occurs to produce upward rotation of the scapula. Supporting Structures of the Acromioclavicular Joint. This motion involves the typical scapulohumeral rhythm: a 2 : 1 ratio of glenohumeral flexion and scapulothoracic upward rotation. all 3 of these muscles can extend the shoulder. Upward and Downward Rotation This type of injury often results from a traumatic anterior dislocation of the humerus. 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. The following provides a summary of normal kinematic interactions among the humerus, the scapula, and the clavicle during common shoulder motions. Terms of Use Examples of these actions include a rowing motion or a push-up. All the more reason to know how the shoulder muscles tasked with supporting this vital joint are supposed to function. When it comes to complex shoulder and elbow surgeries, 3D anatomical modeling can be used to help a surgeon plan the surgery […] • Upward rotation of the scapula (The term elevation is frequently used in the literature without differentiation between abduction and flexion.… However, everyone is not made the same way. The cooperative nature of the shoulder musculature increases the versatility, control, and range of active movements available to the upper extremity. Figure 4-13 The right glenohumeral joint showing the conventional osteokinematic motions of the humerus. And lack of mobility across any of these three joint systems is enough to screw up shoulder function. 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. • Coracohumeral Ligament: Attaches between the coracoid process and the anterior side of the greater tubercle. Symptoms of SLAP lesions often involve pain with overhead activities and “clicking” or “popping” of the shoulder. Any scapular dyskinesis, or alterations of normal position or motion, directly affect the glenohumeral joint and overall shoulder positioning. The humeral head fits better against the glenoid fossa, and the ligaments and muscles (in particular, the supraspinatus) are more optimally aligned to promote proper shoulder mechanics. The full 180 degrees of abduction normally attained at the shoulder is the summation of 120 degrees of GH joint abduction and 60 degrees of scapular upward rotation (Figure 4-15). • Cite the normal ranges of motion for shoulder flexion and extension, abduction and adduction, and internal and external rotation. Shoulder abduction in the scapular plane, often referred to as scaption, positions the greater tuberosity of the humerus under the highest point of the acromion and helps to prevent bony impingement, regardless of the amount of rotation of the glenohumeral joint. Way to prevent recurring impingement bone is the point of attachment for several muscles and attached. Internal rotator muscles, these ligaments help suspend the scapula ( and attached humerus ) to the alternate name the... 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