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©2014 ASRT. All rights reserved. Sectional Anatomy Essentials: Module 9

Sectional Anatomy Essentials – Module 9: The Extremities

1. The Extremities Welcome to Sectional Anatomy Essentials – Module 9: The Extremities. This module was written by Michael A. Manders, BS, R.R.A., R.T.(R), and Terry T. Brown, MD, MS.

2. License Agreement and Disclaimer

3. Objectives After completing this module, you will be able to:

Identify and describe the bones that make up the shoulder, elbow, wrist, hip, knee and ankle joints.

Describe the origin, insertion and action of the muscles of the shoulder, elbow, wrist, hip, knee and ankle joints.

Describe the major ligaments and tendons of the shoulder, elbow, wrist, hip, knee and ankle joints.

Identify the anatomical structures displayed on radiographic scans of the shoulder, elbow, wrist, hip, knee and ankle joints.

List the modalities used to image upper and lower extremity joints, as well as their advantages and disadvantages.

4. Introduction Throughout the Sectional Anatomy Essentials series, we display most of the cross-sectional anatomy using multidetector computed tomography (CT) and magnetic resonance (MR) images to illustrate the three-dimensional relationship of the structures. Use the slider bar in this animation to scroll through the images. Because you can easily lose your frame of reference when viewing cross-sectional images, the location of the featured slice on many slides will be displayed on adjacent localizer images of the other 2 planes, like the image shown here. Click on the next button when you are ready to proceed.

5. Sectional Anatomy of the Extremities The most complex structures of the extremities are undoubtedly major joints such as the shoulder, elbow, wrist, hip, knee and ankle. Major muscles, vasculature, nerves and ligaments all cross these joints. Sectional imaging of the extremities often focuses on these structures since ligament tears, dislocations and fractures are common pathologies that occur in the joints. This module covers the 6 major joints of the body. We’ll begin first with the shoulder.

6. The Shoulder The shoulder girdles are complex structures that connect the upper extremities to the axial skeleton. Each shoulder comprises large bones, joints, ligaments, tendons, muscles, nerves, blood vessels and bursae. We’ll first discuss the bony anatomy of the shoulder: the humerus, the clavicle and the scapula.

7. Humerus The humerus is the long bone of the upper arm. Proximally, the head of the humerus articulates with the glenoid fossa, a depression in the scapula. Distally, the humerus forms a hinge joint with the ulna. Important landmarks of the humerus include the greater tubercle, lesser tubercle, bicipital groove, anatomic neck and surgical neck.


The tubercles project from the humeral head and serve as insertion points for several tendons and ligaments. The greater tubercle is located on the anterolateral humeral head, and the lesser tubercle is located proximally and anteriorly. The bicipital, or intertubercular, groove separates the greater and lesser tubercles. This groove contains the long head of the biceps tendon, as well as the anterolateral branches of the circumflex artery and vein. The roof of the groove is formed by an extended expanse of the subscapularis tendon called the transverse ligament. The anatomic neck of the humerus is located at the region of the fused epiphyseal plate and the attachment of the joint capsule. It runs along the base of the articular surface. The surgical neck lies outside the joint capsule and distal to the greater and lesser tubercles, approximately 2 cm from the anatomical neck. It is the most common site of proximal humeral fractures.

8. Scapula The scapula is a triangular-shaped flat bone on the posterior aspect of the shoulder girdle. Scapular landmarks include the scapular spine, acromion process, coracoid process and glenoid fossa. The scapular spine is a bony ridge running horizontally on the posterior surface of the scapula. It separates the supraspinous fossa from the infraspinous fossa and teres minor. These areas of the scapula are insertion sites for several muscles and ligaments, which we’ll discuss later in the module. The acromion process, or acromion, is a flat bony continuation of the scapular spine that forms an arch running cephalad to the humeral head. In 2% to 10% of the population, an ossification center of the acromion does not fuse, an anatomic variant known as an os acromiale. In 60% of cases, os acromiale is a bilateral finding. The coracoid process is a protuberance extending from the anterior aspect of the scapula near the anterior superior glenoid rim. Along with the acromion, the coracoid process forms the roof of the shoulder joint, the coracoacromial arch. The glenoid fossa is a shallow, oval-shaped recess in the scapula that articulates with the humeral head to form the glenohumeral joint. A fibrocartilaginous ring called the labrum surrounds the rim of the glenoid, making the cavity deeper and broader so that the humeral head can fit more securely into the socket.

9. Clavicle The clavicle is a linear bone that runs horizontally in the coronal plane. It articulates medially with the sternum to form the sternoclavicular joint and laterally with the acromion to form the acromioclavicular joint. The clavicle is capable of up to 20 degrees of movement.

10. Glenohumeral Joint The glenohumeral joint is the main shoulder joint. It is a complex, unstable synovial joint capable of a wide range of motion and is formed where the hemispherical portion of the humeral head fits into the glenoid fossa.


Like other major joints, the glenohumeral joint is enclosed by a fibrous capsule that connects the humerus to the glenoid. The ligaments of the joint capsule provide the main source of stability for the shoulder to prevent dislocation. The articulating portions of the humeral head and the glenoid fossa are protected by articular cartilage. Articular cartilage has a rubbery, slippery surface that absorbs shock and makes motion easier.

11. Glenohumeral Joint In addition to the joint capsule, the glenohumeral joint is stabilized superiorly by the coracoacromial arch and posteriorly by the infraspinatus tendon, teres minor tendon, posterior labrum and inferior glenohumeral ligament. Anteriorly, it is supported by the subscapularis tendon, anterior labrum and the superior, middle and inferior glenohumeral ligaments. The 3 glenohumeral ligaments thicken the joint capsule and help form the labrum. The anatomy of the shoulder overlaps some of these structures, but later slides will include clear images of the ligaments and tendons discussed here.

12. Acromioclavicular Joint The acromion and the clavicle form the acromioclavicular joint. This synovial-lined joint is enclosed by a joint capsule and protected by articular cartilage. The coracoclavicular ligaments attach the clavicle to the scapula at the coracoid process.

13. Shoulder Animation Scroll through this animation to see all of the bony structures of the shoulder that we just discussed.

14. Shoulder Muscles Muscles of the shoulder are divided into 3 groups: the intrinsic muscles, extrinsic muscles and additional muscles. A group of 4 intrinsic muscles surround the humeral head and constitute the rotator cuff: the subscapularis, supraspinatus, infraspinatus and teres minor. These muscles help raise the arm and rotate it in many directions. The tendons of the rotator cuff form a continuous sheath that attaches to the humerus. The extrinsic muscles include the trapezius, latissimus dorsi, levator scapulae, rhomboid major and rhomboid minor, serratus anterior, subclavius, omohyoid, pectoralis major and pectoralis minor. Finally, the additional muscles do not fit easily into either the intrinsic or extrinsic groups. These muscles include the deltoids, triceps, biceps and coracobrachialis. Let’s look at a few of the major muscles of the shoulder.

15. Trapezius The trapezius is a large, flat muscle that covers the upper back and shoulders and suspends the shoulder complex from the base of the skull. The muscle originates from the superior nuchal line of the occipital bone of the skull, the external occipital protuberance, ligamentum nuchae and from the spinous processes of C7 and T1 through T12. The upper portion of the trapezius inserts on the lateral third of the clavicle, the acromion and on the upper border of the scapular spine.


The lower portion of the trapezius is directed upward and inserts on the medial portion of the scapular spine. The trapezius is the major support of the overall structural integrity of the shoulder. The superior portion of the trapezius elevates the scapula. The lower portion of the trapezius pulls the medial aspect of the scapular spine inferiorly. This action rotates the glenoid fossa in an upward and forward direction.

16. Trapezius Animation Scroll through this animation to see the trapezius that we just discussed.

17. Deltoid The triangular-shaped deltoid is the strongest muscle of the shoulder. It forms a cap over the humeral head, producing the outer, rounded contour of the shoulder. The deltoid is divided into 3 parts, each with a different origin. The clavicular, or anterior, part originates anteriorly from the lateral third of the clavicle. The acromial, or middle, head arises on the lateral margin of the acromion. The spinal, or posterior, part originates on the lower portion of the scapular spine. The parts join and insert on the deltoid tuberosity of the humerus. The deltoid functions to abduct the arm, primarily by action of the middle head. The anterior head stabilizes the humerus during abduction and helps to flex and medially rotate the arm. The posterior head also stabilizes the humerus during abduction, in addition to helping extend and laterally rotate the arm.

18. Deltoid Animation Scroll through this animation to see the deltoid that we just discussed.

19. Supraspinatus The supraspinatus muscle is a portion of the rotator cuff that lies draped over the superior aspect of the humeral head. It originates from the supraspinatus fossa of the scapula and inserts on the upper aspect of the greater tubercle of the humerus. The supraspinatus abducts the arm, mainly over the first 10 degrees of abduction. It fixes the humeral head against the glenoid and allows the larger deltoid muscle to complete the abduction.

20. Supraspinatus Animation Scroll through this animation to see the supraspinatus that we just discussed.

21. Subscapularis The subscapularis is a flat muscle that forms the anterior aspect of the rotator cuff. It originates from the subscapular fossa on the anterior aspect of the scapula. The subscapularis inserts on the lesser tuberosity of the humerus. The subscapularis rotates the arm medially and stabilizes the shoulder joint.

22. Subscapularis Animation Scroll through this animation to see the subscapularis that we just discussed.


23. Teres Minor The teres minor is a flat muscle that acts in opposition to the subscapularis. It originates from the posterior superior border of the scapula and inserts on the lower aspect of the greater tubercle of the humerus. The teres minor rotates the shoulder laterally, in addition to providing stabilization and support.

24. Teres Major The teres major originates from the inferior third of the dorsal lateral border of the scapula and inserts on the medial wall of the bicipital groove. The teres major acts to medially rotate and adduct the arm.

25. Latissimus Dorsi The latissimus dorsi is a large, flat triangular muscle located over the lower thorax and extending into the lumbar region. It originates from the posterior aspect of the iliac crest, the lower 3 or 4 ribs and the spinous processes of T6 through T12, where it runs deep to the trapezius. The muscle inserts into the bicipital groove after wrapping around the lower margin of the teres major. The latissimus dorsi acts to adduct, medially rotate and extend the arm.

26. Major Bursae of the Shoulder A bursa is a synovial sac filled with fluid that helps cushion the joint and alleviate friction. There are 3 major bursae in the shoulder: the subacromial-subdeltoid, the subcoracoid and the infraspinatus. The subacromial-subdeltoid bursa overlies the rotator cuff on the undersurface of the acromion. In its normal state, this bursa should have only a trace amount of fluid. The subcoracoid bursa lies between the tendon of the subscapularis and the short head of the biceps and coracobrachialis tendons. Although the subcoracoid bursa can communicate with the subacromial-subdeltoid bursa, it does not normally communicate with the joint.

27. Arteries of the Shoulder The shoulder receives its vascular supply from branches of the axillary artery. The axillary artery is the continuation of the subclavian artery. It begins at the lateral margin of the first rib and ends at the lower margin of the teres major muscle.

28. Nerves of the Shoulder The upper extremity is innervated by the brachial plexus, which is formed in the posterior triangle of the neck from the anterior rami of the fifth through eighth cervical nerves and the first thoracic spinal nerve. The brachial plexus is divided into 5 roots, 3 trunks, 6 divisions and 3 cords, which are successively smaller and more specific units.

29. Radiography of the Joints Radiography is the most basic and widely used imaging modality to assess joint pathology such as fractures, dislocations, arthritis and neoplasms of the bony structures. Arthrography can provide additional diagnostic information concerning joints. Arthrography is performed using radiography, fluoroscopy, magnetic resonance (MR) imaging or computed tomography (CT).


30. MR of the Joints MR imaging is the next most widely used modality for joint assessment. MR provides excellent information about the soft tissues and is most commonly used to detect pathology involving anatomical structures that stabilize the joint such as the rotator cuff, articular cartilage, joint capsule, muscular envelope and synovial membrane.

31. CT of the Joints CT is superior to MR for evaluating the bony contours of the joint and therefore can be used to detect subtle fractures, assess fracture healing and evaluate the bony cortex.

32. Ultrasonography of the Joints Ultrasound imaging is a noninvasive way to evaluate joints that is faster than MR and unlike CT and radiography does not involve exposure to ionizing radiation. Ultrasound usage is mostly confined to evaluating the integrity of ligaments and other muscular structures of the joint. It also can be used to detect pathology such as synovial proliferation, hematomas and abscess formation.

33. Nuclear Medicine Imaging of the Joints Nuclear medicine imaging including bone scans, white cell scans and positron emission tomography (PET) have limited but significant usefulness in evaluating joints. These methods are used to detect abnormalities of metabolism associated with fractures, arthritis, infection, vascular abnormalities or neoplasms.

34. Knowledge Check Answer the following question.



37. The Elbow The elbow is a complex joint with 3 articulations involving the humerus, radius and ulna. Each of the articulations allows different types of motion. The humeroulnar articulation consists of the trochlea of the humerus and the trochlear notch of the ulna. This hinge-type joint permits flexion and extension. The humeroradial articulation occurs where the capitulum of the humerus meets the head of the radius. This unstable joint allows for hinge-like flexion and extension, as well as rotation and pivoting. The proximal radioulnar articulation includes the head of the radius and the sigmoid notch of the ulna. This joint allows the radial head to rotate during supination and pronation of the forearm. The relationship of the elbow’s bony structures varies over the range of motion. The bones are in their most stable position with the elbow in about 90 degrees flexion and midway between supination and pronation. The entire elbow joint is surrounded by a synovium-lined joint capsule. The fibrous capsule encloses the anterior and posterior fat pads, which are extrasynovial and intracapsular.


38. Humerus Landmarks for the distal humerus include the medial and lateral epicondyles, olecranon fossa, trochlea and capitulum. The medial epicondyle is located on the ulnar aspect of the humerus and serves as an attachment point for the common flexor tendon that flexes the wrist. The lateral epicondyle is located on the radial aspect of the humerus and provides an attachment site for the common extensor tendon that extends the wrist. The olecranon fossa is a shallow, bowl-shaped area that allows the olecranon process of the ulna to pivot anteriorly without impacting the humerus during elbow extension. It also stabilizes the elbow from medial or lateral translocation of the ulna and humerus. The capitulum is the radial aspect of the humeral epiphysis that articulates with the radial head. The trochlea is the semicylindrical ulnar aspect of the distal humeral epiphysis that articulates with the proximal ulna in the trochlear notch. Both the capitulum and trochlea are covered with articular cartilage.

39. Ulna and Radius The ulna is located medially within the forearm. Its proximal landmarks include the olecranon and coronoid processes and the trochlear notch. The olecranon process is a hook-shaped projection that makes up the bony tip of the elbow. Its anterior surface forms the trochlear notch, a roughly hemi-cylindrical groove that holds the trochlea of the humerus. This articulation is located on the posterior aspect of the elbow with the trochlear notch directed anteriorly. The coronoid process is a triangular-shaped protuberance that extends from the anterior aspect of the proximal ulna and forms an extension of the distal wall of the trochlear notch. This structure provides increased stability for the elbow joint when the elbow is in full extension. The radius is located laterally within the forearm. The radial head is the proximal epiphysis of the radius bone. It is covered with articular cartilage and is shaped roughly like the head of a hammer. The radial head contains a bowl-shaped depression known as the fovea into which the capitulum of the humerus can articulate and rotate. The neck of the radius is a narrowing of the proximal radius just beyond the radial head and proximal to the radial tuberosity. The radial tuberosity is a ridge-like protuberance from the ulnar aspect of the proximal radius just distal to the radial neck.

40. Elbow Animation Scroll through this animation to see the bony structures of the elbow that we just discussed.

41. Muscles of the Elbow The movement of the elbow is the result of the action of multiple muscles. Muscles involved in flexion of the elbow include the brachialis, biceps brachii, pronator teres and brachioradialis muscles. The brachialis muscle originates on the anterior surface of the humeral diaphysis and inserts on the anterior tuberosity of the ulna. The biceps brachii muscle crosses 2 joints in that it originates at the shoulder and inserts on the radial tuberosity. In addition to flexing the elbow, the biceps brachii extends the shoulder. The brachioradialis muscle originates from the lateral supracondylar ridge of the humerus and inserts on the lateral aspect of the distal radius. The triceps and anconeus muscles provide elbow extension. The triceps muscle is the largest muscle in the upper arm and originates from multiple attachments in the shoulder and proximal humerus. It inserts on the olecranon process.

42. Pronator Teres and Pronator Quadratus As their names suggest, the pronator teres and the pronator quadratus muscles are involved in pronation. The pronator teres originates on the medial epicondyle of the humerus and the


coronoid process of the ulna. It inserts on the lateral side of the midshaft of the radius. The pronator quadratus muscle is not a part of the elbow because it’s located in the distal forearm; however, this muscle helps to pronate the forearm. The pronator quadratus originates on the distal ulna and inserts on the distal radius. Supination is accomplished by the biceps brachii and supinator muscles. The supinator muscle originates from the lateral epicondyle of the humerus as well as the supinator crest of the ulna. It inserts on the lateral aspect of the proximal diaphysis of the radius and acts to supinate the forearm.

43. Elbow Animation Scroll through this animation to see some of the muscular structures of the elbow that we just discussed as well as the muscles of the proximal forearm.

44. Ligaments of the Elbow The elbow is stabilized by an extensive network of ligaments. The major ligaments of the elbow include the radial collateral, lateral ulnar collateral, ulnar collateral, anular and quadrate ligaments. The radial collateral ligament originates on the lateral epicondyle. Distally, it joins the anular ligament and acts in opposition to varus stress on the elbow. The lateral ulnar collateral ligament also originates on the lateral humeral epicondyle. Inserting just posterior to the radial collateral ligament, it runs posteriorly and medially behind the radial neck and inserts on the supinator crest of the proximal ulna. This ligament protects the elbow against posteromedial instability. The ulnar collateral ligament extends from the medial epicondyle to the ulna. It has 3 components: the anterior band, transverse band and posterior band. Of these, the anterior band is clinically the most strongest and important. It protects the elbow against valgus stress. A key part of the proximal radioulnar joint, the anular ligament is attached to the anterior and posterior aspects of the radial notch. It forms a ring around the radial head, holding the head in place and allowing it to rotate on the capitulum. The quadrate ligament extends from the radial neck to the ulna. It is distal to the anular ligament and helps to stabilize the proximal radioulnar joint.

45. Arteries of the Elbow The brachial artery is the continuation of the axillary artery and is the main source of blood supply to the arm. Located in the cubital fossa, the artery runs with the median nerve medial to the biceps tendon. It is protected by the biceps aponeurosis. The brachial artery divides distally into the radial and ulnar arteries at the level of the radial neck. Branches of the brachial artery include the deep brachial, the superior ulnar collateral and the inferior ulnar collateral arteries. The deep brachial branch has anterior and posterior branches and forms an anastomosis. The superior ulnar collateral branch runs posterior to the medial condyle and forms a network with the branches of the ulnar artery. The inferior ulnar collateral branch arises distal to the superior ulnar collateral artery and also forms an anastomosis with branches of the ulnar artery.

46. Veins of the Elbow The 2 important veins at the level of the elbow are the cephalic and the basilic veins. The cephalic vein lies on the lateral aspect of the biceps while the basilic vein lies medial to the biceps.

47. Nerves of the Elbow The important nerves of the elbow are the radial, median and ulnar. The radial nerve arises from the posterior cord of the brachial plexus and innervates the triceps, anconeus, brachioradialis


and the lateral portion of the brachialis muscles. It divides into deep and superficial branches at the level of the lateral epicondyle. The median nerve originates from the medial and lateral cords of the brachial plexus. It innervates the pronator teres muscle, pronator quadratus muscles and portions of the flexor compartment on the anterior aspect of the forearm. The ulnar nerve arises from the medial cord of the brachial plexus and provides articular branches to the elbow joint. In the forearm, it divides into superficial and deep branches, innervating the flexor carpi ulnaris and the medial aspect of the flexor digitorum profundus.





52. The Wrist The wrist typically is considered to be the joints from the distal radioulnar joint through the carpometacarpal joints. The wrist bones include the distal radius and ulna, 8 carpal bones and the proximal portions of the 5 metacarpals. The wrist is composed of a complex set of articulating bones and associated tendons, ligaments, vascular structures and nerves. These structures allow the wrist to perform flexion, extension, radial and ulnar deviation, as well as pronation and supination.

53. Bony Structures of the Wrist The bony structures of the wrist include the distal radius and ulna, which articulate with one another. The radius articulates with the first of 2 carpal rows, but a fibrocartilginous ligament called the articular disk prevents the ulna from articulating with the carpus. From radius to ulna, the proximal carpal row includes the scaphoid, the lunate, the triquetrum and the pisiform. The distal carpal row comprises the trapezium, the trapezoid, the capitate and the hamate.

54. Wrist Animation Scroll through this animation to see the bony structures of the wrist that we just discussed.

55. Ligaments of the Wrist The wrist ligaments can be classified as extrinsic or intrinsic. The extrinsic ligaments attach the carpus to the radius and ulna or to the metacarpals. The intrinsic ligaments attach the carpal bones to each other. The 23 wrist ligaments are named according to their location and the 2 bones they attach to. For example, the ligament on the dorsal aspect of the wrist that attaches to the scaphoid and trapezoid is called the dorsal scaphotrapezoidal ligament. The ligaments on the volar aspect of the wrist are the major stabilizers of the joint.


56. Muscles of the Wrist and Hand The muscles of the wrist and hand can be organized by their action on the wrist, palm and fingers. Grossly, these categories are the superficial flexors, deep flexors, superficial extensors, deep extensors, thenar and hypothenar muscles. The superficial flexors include the flexor carpi radialis, palmaris longus, flexor carpi ulnaris and flexor digitorum superficialis. These all originate, at least in part, on the medial epicondyle. The superficial extensors include the brachioradialis, extensor carpi radialis longus, extensor digitorum and extensor ulnaris. Most of these muscles originate on the proximal humerus and insert at the base of the radial styloid process, the base of the metacarpals or on the middle and distal phalanges.

57. Wrist Animation Scroll through this animation to see some of the structures of the wrist.

58. The Carpal Tunnel The carpal tunnel contains the flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus and median nerve. It is bounded dorsally by the carpal bones, volarly by the flexor retinaculum, medially by the hook of the hamate and pisiform, laterally by the scaphoid and trapezium, proximally by the radiocarpal joint and distally by the bases of the metacarpal bones. The surrounding structures form a restricted space that can sometimes impinge on the median nerve and become clinically significant.

59. Knowledge Check

Answer the following question.




63. Knowledge Check


64. The Hip Joint A complex synovial joint capable of a wide range of movement, the hip joint supports the weight of the body both during movement and while standing still. It consists of the rounded portion of the femoral head which articulates with the cup-like acetabulum of the pelvis. The articulating portions of the femoral head and the acetabulum are protected by articular cartilage.

65. The Acetabulum The acetabula of the pelvis are bilateral concave cavities. Each acetabulum is formed by the 3 bones of the pelvis: the ischium, the ilium and the pubis. The ischium makes up a little more than two-fifths of the acetabulum and forms the superior border of the structure. The ilium makes up a little less than two-fifths of the acetabulum and creates the posterior border and part of the middle. The pubis makes up about one-fifth of the acetabulum and forms the


anterior border and a portion of the middle. Most of the periphery of the acetabulum is surrounded by a fibrocartilaginous rim known as the acetabular labrum. The labrum increases the depth of the acetabular cavity, which improves the articulation between the acetabulum and the femoral head. The middle of each acetabulum contains a circular indentation called the acetabular fossa. The acetabular fossa is continuous with a deep depression in the inferior border of the acetabulum known as the acetabular notch. The acetabular labrum doesn’t extend across the acetabular notch. Instead, the transverse acetabular ligament connects the 2 ends of the labrum.

66. The Proximal Femur The femur is the long bone in the upper leg. Important landmarks of the femur include the femoral head, greater trochanter and lesser trochanter. The ball-shaped femoral head is the most superior portion of the bone. The majority of the femoral head is smooth and covered by articular cartilage, except for a small indentation inferoposterior to the center known as the fovea capitis femoris. The fovea capitis femoris is the attachment point for the ligamentum teres, which we’ll discuss later in the module. The neck of the femur extends inferolaterally from the femoral head and connects the femoral head to the longitudinally oriented femoral shaft. Two bony processes arise from the base of the femoral neck: the greater trochanter and the lesser trochanter. The greater trochanter arises from the lateral border of the femoral neck and extends slightly superiorly, laterally and posteriorly. The greater trochanter serves as the attachment point for tendons of some of the large muscles of the pelvis. The lesser trochanter arises from the medial border of the base of the femoral neck and extends slightly posteriorly and also serves as the attachment point for tendons.

67. Ligaments of the Hip Joint Like the shoulder and elbow joints, the hip joint is stabilized by multiple ligaments, which can be characterized as extracapsular or intracapsular. The 3 extracapsular ligaments include the iliofemoral, the pubofemoral and the ischiofemoral ligaments. The ischiofemoral ligament encapsulates the posterior portion of the hip joint and cannot be seen on this image.

68. Ligamentum Teres The ligamentum teres is the sole intracapsular ligament. It is a triangular-shaped ligament that attaches to the fovea capitis femoris of the femoral head. The other 2 points of attachment are each side of the acetabular notch. The ligamentum teres limits adduction of the hip.

69. Hip Animation The next 3 slides contain images of the hip. Scroll through these animations to see some of the bony structures of the hip joint that we just discussed.

70. Hip Animation Scroll through this animation to see some of the bony structures of the hip joint that we just discussed.

71. Hip Animation Scroll through this animation to see some of the bony structures of the hip joint that we just discussed.


72. Muscles of the Hip Joint The hip muscles can be divided into 4 groups: the adductor, gluteal, iliopsoas and lateral rotator muscles.

73. Adductor Muscles of the Hip The adductor muscle group is located medial to the femur and includes 5 muscles that are responsible for adducting the hip. In addition to adduction, these muscles help the hip move in several other directions. The adductor longus, adductor magnus and adductor brevis all laterally rotate the hip. The adductor longus and the pectineus flex the hip, while the adductor magnus extends the structure. The gracilis primarily flexes and medially rotates the knee.

74. Hip Animation Scroll through this animation to see the adductor muscles of the hip that we just discussed.

75. Gluteal Muscles The gluteal group is located posterior to the femur and consists of 4 muscles. The gluteus maximus muscle is primarily responsible for holding the pelvis and torso onto the femoral head. It also straightens the thigh into a parallel line with the body. The gluteus medius and gluteus minimus work together to abduct the leg away from midline and externally rotate the hip. With the hip flexed, these muscles internally rotate the hip. Each tensor fasciae latae medially rotates and flexes the hip. In addition, the muscles stabilize the hip and knee while standing and laterally rotate the leg at the knee.

76. Hip Animation Scroll through this animation to see the gluteal muscles of the hip that we just discussed.

77. Iliopsoas Muscles The iliopsoas muscle group consists of 2 muscles: the psoas major and the iliacus muscles. The psoas muscles are long fusiform muscles located on either side of the lumbar spine. Although the iliacus and psoas are 2 distinct muscles in the upper pelvis, by time they reach the inferior pelvis, it is difficult to differentiate between them. Each iliopsoas muscle is responsible for flexing the thigh and the torso.

78. Hip Animation Scroll through this animation to see the iliopsoas muscle of the hip that we just discussed.

79. Lateral Muscles of the Hip The lateral group of hip muscles originates near the acetabulum and inserts near the greater trochanter. Six muscles make up the group. The obturator internus muscles laterally rotate and abduct the thigh away from midline if the hip is flexed. The obturator internus muscles also help to stabilize the hip joint. The obturator externus rotate the thigh laterally and adduct the thigh toward the midline. The quadratus femoris also laterally rotate and adduct the thigh. The piriformis helps to rotate the thigh laterally and abduct it away from midline if the hip is flexed. Finally, the superior and inferior gemelli laterally rotate the hip and abduct the thigh away from midline if the hip is flexed.


80. Hip Animation Scroll through the following 2 animations to see the lateral muscles of the hip that we just discussed.

81. Hip Animation Scroll through this animation to see the remaining lateral muscles of the hip that we just discussed.



84. Knowledge Check


85. The Knee Skeletally, the knee consists of the distal femur, the proximal tibia and the patella. Although not a part of the knee, we’ll discuss the fibula, which along with the tibia makes up the lower leg. The important femoral landmarks with respect to the knee are the articulating bodies: the medial and lateral condyles. Both condyles project slightly distally and posteriorly from the distal femur. The condyles are covered with articular cartilage, which improves articulation with the medial and lateral tibial condyles. The tibia is the larger of the 2 bones of the lower leg. It articulates with the femur proximally via the medial and lateral condyles. The intercondylar eminence, otherwise known as the tibial spine, separates the 2 tibial condyles. Anteriorly, just inferior to the intercondylar eminence, is a raised portion of bone called the tibial tuberosity. The tibial tuberosity and intercondylar eminence serve as attachment points for multiple ligaments and other structures. Centered anterior to the distal femur is the patella, commonly known as the kneecap. The patella is a thick, somewhat triangular sesamoid bone that protects the anterior articular surface of the knee and serves as an attachment point for multiple muscles. The fibula is lateral to the tibia. The smaller of the lower leg bones, the fibula articulates with the tibia proximally at the superior tibiofibular articulation and distally at the inferior tibiofibular articulation. The fibula serves as the attachment point for multiple muscles of the lower leg.

86. Knee Animation Scroll through this animation to see the bony anatomy of the knee that we just discussed.

87. Cartilage and Ligaments of the Knee Like other joints of the body, the knee joint contains cartilage to ensure smooth articulation and movement between the femur and tibia. Fibrous cartilage, also known as the menisci, overlies the medial and lateral tibial condyles. The medial and lateral menisci are crescent-shaped pads of cartilage that disperse body weight and reduce friction during movement. The knee has 3 groups of major ligaments: the cruciate, collateral and patellar ligaments. The cruciate ligaments provide anterior and posterior stability for the knee. The collateral ligaments stabilize the medial and lateral sides of the knee.


88. Patellar Ligament The patellar ligament is actually a portion of the quadriceps femoris tendon. Traveling inferiorly, the tendon reaches the superior border of the patella and flattens to about the width of the patella, extending to the inferior border of the patella before continuing inferiorly. The portion of the fibrous tissue distal to the patella is called the patellar ligament.

89. Knee Animation Scroll through this animation to see the ligaments of the knee that we just discussed.

90. Muscles of the Knee Multiple muscles are involved in the movement of the knee, including the quadriceps femoris group, the sartorius, the hamstring group and the popliteus.

91. Quadriceps Femoris Muscle Group The quadriceps femoris muscle group makes up the majority of the anterior thigh. The group consists of 4 muscles sharing an insertion point on the tibial tuberosity via the patellar ligament. The rectus femoris is responsible for the flexion of the hip and extension of the knee. The vastus lateralis, vastus intermedius and vastus medialis act to extend the knee.

92. Sartorius Known as the longest muscle in the body, the sartorius muscle also is located in the anterior thigh. It originates from the anterior superior iliac spine and extends inferiorly and medially across the anterior thigh until it reaches the medial knee area. The sartorius plays a role in flexing, adducting, abducting and laterally rotating the hip, as well as flexing the knee.

93. Hamstring Muscle Group The hamstring muscle group makes up a portion of the posterior thigh. The group consists of 3 muscles. The biceps femoris has 2 heads. The long head of the biceps femoris plays a role in extending the hip, while both the long and short heads rotate the lower leg laterally and flex the knee. The semitendinosus and semimembranosus muscles are responsible for extending the hip, flexing the knee and medially rotating the lower leg.

94. Popliteus The popliteus muscle originates from the lateral border of the lateral condyle of the femur and extends laterally, inferiorly and slightly posteriorly until inserting on the posterior border of the body of the tibia. It plays a role in flexing the leg and rotating the tibia inward while the knee is flexed.

95. Knee Animation Scroll through this animation to see the muscles of the knee that we just discussed.




98. The Ankle Skeletally, the ankle is made up of 3 bones: the tibia, the fibula and the talus. When discussing the ankle joint, we’ll focus on the distal ends of the tibia and fibula. The malleoli of these bones are located medially and laterally. The medial malleolus is a bony outgrowth of the distal tibia; the lateral malleolus projects from the distal fibula. The malleoli articulate with the medial and lateral portions of the talus and are responsible in part for stabilizing the ankle. The horizontal part of the distal tibia that articulates with the talus is the tibial plafond. Like articulations in the knee and the hip, these surfaces are covered with articular cartilage. The talus bone completes the ankle joint and is one of the many bones of the foot that we’ll discuss later. The bones of the foot include the tarsus bones, the metatarsus bones and the phalanges. The tarsus bones make up the mid foot. The metatarsus bones include the first through fifth metatarsal bones. The phalanges, or toes, consist of 2 bones in the first digit and 3 bones in the second through fifth digits.

99. Ankle Animation Scroll through this animation to see the bony structures of the ankle that we just discussed.

100. Ligaments of the Ankle and Foot The major ligaments of the ankle and foot stabilize the extremity. These ligaments include the deltoid, the plantar calcaneonavicular, the anterior talofibular, the calcaneofibular, the posterior talofibular, the lateral talocalcaneal and the syndesmosis.

101. Muscles of the Ankle and Foot The muscles of the lower leg can be divided into anterior, posterior, medial and lateral groups.

102. Anterior Muscle Group The anterior group consists of 4 muscles. The tibialis anterior is responsible for dorsiflexion of the ankle and inversion of the foot. The extensor hallucis longus muscle is involved in dorsiflexion of the ankle and extension of the first digit. The extensor digitorum longus muscle aids in dorsiflexion of the ankle, eversion of the foot and extension of the second through fourth digits. Finally, the peroneous tertius muscle is responsible for dorsiflexion of the ankle and eversion of the foot.

103. Ankle Animation Scroll through this animation to see the anterior muscle group that we just discussed.

104. Posterior Muscle Group The posterior muscle group is made up of 6 muscles. The gastrocnemius muscle originates from the posterior borders of the medial and lateral femoral condyles and extends inferiorly before inserting on the posterior surface of the calcaneus via the largest tendon in the body, the Achilles tendon. The gastrocnemius is responsible for plantar flexion of the ankle. The soleus and plantaris muscles also assist in plantar flexion of the ankle. The plantaris muscle is absent in a small percentage of the human population. The tibialis posterior aids in plantar flexion of the ankle and inversion of the foot. The flexor digitorum longus is responsible for flexion of the second through fifth toes, plantar flexion of the ankle and inversion of the foot. Finally, the flexor hallicus longus muscle is responsible for flexion of the first digit, plantar flexion of the ankle and inversion of the foot. The medial muscle group includes the tendons of the posterior


tibialis, flexor hallucis longus and flexor digitorum longus muscles. These tendons cross in the area of the medial malleolus en route to their insertion points on the foot.

105. Ankle Animation Scroll through this animation to see the posterior and medial muscle groups of the ankle that we just discussed.

106. Lateral Muscle Group The lateral muscle group is made up of 2 main muscles. The peroneus longus and the peroneus brevis are both responsible for plantar flexion of the ankle and eversion of the foot.

107. Ankle Animation Scroll through this animation to see the lateral muscle group that we just discussed.

108. Vessels of the Leg As with all muscles, the muscles of the lower extremity need oxygenated blood supplied by the arteries to survive. In the leg, the arterial pathway begins as the continuation of the external iliac artery of the pelvis, called the common femoral artery. The common femoral artery begins at the approximate level of the femoral head and extends inferiorly only a short way before the deep femoral artery branches off to supply blood to the deep tissues of the thigh. After the bifurcation of the deep femoral artery, the common femoral artery continues inferiorly as the superficial femoral artery. At the level of the distal femur, approximately 2 inches superior to the knee, the superficial femoral artery becomes the popliteal artery. Shortly inferior to the knee, the popliteal splits into the anterior and posterior tibial arteries. The anterior tibial artery extends inferiorly, supplying blood to the anterior portion of the lower leg. At the ankle joint, the anterior tibial artery continues as the dorsalis pedis artery, supplying oxygenated blood to the dorsal portion of the foot.

109. Vessels of the Leg The deoxygenated blood of the lower extremities is returned via the common femoral vein. The common femoral vein receives blood from the greater saphenous, popliteal and deep femoral veins. The greater saphenous vein is the longest vein in the body and receives deoxygenated blood from many lower extremity vessels as it extends superiorly to meet the common femoral vein.



112. Knowledge Check

Answer the following question

113. Conclusion This concludes Module 9 – The Extremities. You should now be able to:

Identify and describe the bones that make up the shoulder, elbow, wrist, hip, knee and ankle joints.


Describe the origin, insertion and action of the muscles of the shoulder, elbow, wrist, hip, knee and ankle joints.

Describe the major ligaments and tendons of the shoulder, elbow, wrist, hip, knee and ankle joints.

Identify the anatomical structures displayed on radiographic scans of the shoulder, elbow, wrist, hip, knee and ankle joints.

List the modalities used to image upper and lower extremity joints, as well as their advantages and disadvantages.

114. Resources 115. Development Team 116. Acknowledgements 117. Module Completion

for educational and institutional use. this test bank is...

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