KIN 301 Chapter 5
glenoid labrum
a cartilaginous ring that surrounds the glenoid fossa just inside its periphery
the shoulder joint (glenohumeral joint) is
a multiaxial ball-and-socket joint classified as enarthrodial
the glenohumeral joint is paired with the shoulder girdle to
accomplish the total shoulder range of motion
the muscles of the shoulder joint are
all innervated by the nerves of the brachial plexus
muscles that originate on the scapula and clavicle and insert on the humerus may be thought of
as muscles intrinsic to the glenohumeral joint
the long head of the triceps brachii
assists in extension and horizontal abduction
the biceps brachii
assists in flexing and horizontally adducting the shoulder
adduction
downward movement of the humerus in the frontal plane medially toward the body from abduction
their point of insertions
enables them to rotate the humerus, an essential movement in this freely movable joint
its stability is
enhanced by the glenoid labrum
muscles originating on the trunk and inserting on the humerus are considered
extrinsic to the glenohumeral joint
GIRD stands for
glenohumeral internal rotation deficit
the biceps brachii and triceps brachii (long head) are also
involved in glenohumeral movements
the shoulder is often injured because of
its anatomical design
horizontal abduction (extension)
movement of the humerus in a horizontal or transverse plane away from the chest
horizontal adduction (flexion)
movement of the humerus in a horizontal or transverse plane toward and across the chest
internal rotation
movement of the humerus in the transverse plane medially around its long axis toward the midline
external rotation
movement of the humerus laterally in the transverse plane around its long axis away from the midline
flexion
movement of the humerus straight anteriorly from any point in the sagittal plane
extension
movement of the humerus straight posteriorly from any point in the sagittal plane, sometimes referred to as hyperextension
the shoulder joint
moves in all planes and is the most movable joint in the body
the price of mobility is
reduced stability
GIRD
represents a difference in internal rotation range of motion between an individual's throwing and nonthrowing shoulders
the scapula, clavicle, and humerus
serve as attachments for most of the muscles of the shoulder joint
the glenohumeral joint is
similar to the hip in its joint; however, the socket provided by the glenoid fossa is much shallower and relatively small in comparison to the rather large humeral head
determining the exact range of movement for the glenohumeral joint is difficult because of
the accompanying shoulder girdle movement
they are small muscles whose tendons cross
the front, top, and rear of the head of the humerus to attach not the lesser and greater tubercles
while the exact number of degrees in one segment compared to another may vary within and between individuals,
the generally accepted ratio is 2 to 1; that is, for every 2 degrees of glenohumeral motion, there is 1 degree of scapula motion
the shoulder joint is also known as
the glenohumeral joint
it is further stabilized by
the glenohumeral ligaments, especially anteriorly and inferiorly
the more stable a joint is,
the less mobile it is
the more mobile a joint is,
the less stable it is
due to the wide range of motion involved in the glenohumeral joint,
the ligaments are quite lax until the extreme ranges of motion are reached
this relative lack of static stability provided by the ligaments emphasizes
the need for optimal dynamic stability to be provided by muscles such as the rotator cuff group
the subscpularis, supraspinatus, infraspinatus, and teres minor muscles make up
the rotator cuff
the only attachment of the shoulder joint to the axial skeleton is via
the scapula and its attachment through the clavicle at the sternoclavicle joint
rotator cuff impingement syndrome occurs when
the tendons of these muscles, particularly the supraspinatus and infraspinatus, become irritated and inflamed as they pass through the subacromial space between the acromion process of the scapula and the head of the humerus
stability is sacrificed
to gain mobility
another frequent injury is
to the rotator cuff
abduction
upward lateral movement of the humerus in the frontal plane out to the side, away from the body
if the shoulder girdle is free to move, then the total range of combined joints is
~170 to 180 degrees of abduction ~170 to 180 degrees of flexion ~140 to 150 degrees of horizontal adduction
if the shoulder girdle is prevented from moving, then the glenohumeral joint movements are generally thought to be in the following ranges:
~90 to 100 degrees of abduction ~0 degrees adduction or 70 degrees anterior of the trunk ~40 to 60 degrees of extension ~90 to 100 degrees of flexion ~70 to 90 degrees of internal and external rotation ~45 degrees of horizontal abduction ~135 degrees of horizontal adduction
shoulder joint muscles - location - superior
~deltoid ~supraspinatus
movements of the shoulder joint (glenohumeral joint)
~flexion ~extension ~abduction ~adduction ~external rotation ~internal rotation ~horizontal abduction (extension) ~horizontal adduction (flexion)
shoulder joint muscles - location - posterior
~latissimus dorsi ~teres major ~infraspinatus ~teres minor
shoulder joint muscles - location -anterior
~pectoralis major ~coracobrachialis ~subscapularis
the rotator cuff group includes
~subscapularis ~supraspinatus ~infraspinatus ~teres minor
scapular landmarks
~supraspinous fossa ~infraspinous fossa ~subscapular fossa ~spine of the scapula ~glenoid cavity ~coracoid process ~acromion process ~inferior angle
the intrinsic muscles include
~the deltoid ~the coracobrachialis ~the teres major ~the rotator cuff group
humeral landmarks
~the head ~greater tubercle ~lesser tubercle ~intertubercular groove ~deltoid tuberosity
extrinsic glenohumeral muscles are
~the latissimus dorsi ~the pectoralis major
a number of factors contribute to its injury rate, including
~the shallowness of the glenoid fossa ~the laxity of the ligamentous structures necessary to accommodate its wide range of motion ~the lack of strength and endurance in the muscles, which are essential in providing dynamic stability to the joint