Page 65 - ASOP ROT Study Guide

9 . 3 Axes of Movement

The shoulder girdle can be moved in several directions on the chest wall. This ability together with
the large range of movement possible at the shoulder joint (correctly called the glenohumeral
joint) allows the arm to be moved into many positions.

The combination of scapulothoracic and glenohumeral movement, make the shoulder joint the most
mobile in the body. The different axes of movements allow movements in the:

♦ coronal plane
♦ sagittal plane

In addition, rotation along the long axis of the humerus is possible.

9 . 4 Types of Movement

♦ Flexion - swinging the arm forwards in the sagittal plane
♦ Extension - swinging the arm backwards in the sagittal plane.
♦ Abduction - swinging the arm laterally in the coronal plane.
♦ Adduction - swinging the arm medially in the coronal plane.
♦ Internal rotation - rotation of the arm along its long axis so that the hand turns towards the

body.
♦ External rotation - rotation of the arm along its long axis so that the hand turns away from the

body.
♦ Circumduction - movements of the whole arm in a circle (a combination of flexion, abduction,

extension and adduction).

9 . 5 Muscles

When thinking of muscles controlling the shoulder joint, we must think of those which move the
shoulder girdle and those which move the glenohumeral joint. In addition, the rotator cuff muscles
also stabilize the glenohumeral joint while other muscles move it.

Muscle actions:

♦ trapezius - rotates the scapula upwards and shrugs the shoulders.
♦ serratus anterior - stabilises the scapula to the chest wall and pulls it forwards.
♦ pectoralis major - flexes and adducts the glenohumeral joint.
♦ latissimus dorsi - extends and adducts the glenohumeral joint.
♦ deltoid - abducts the glenohumeral joint.
♦ rotator cuff - these four muscles stabilise the glenohumeral joint during movement and

when acting individually, can abduct, extend and rotate the joint.

9 . 6 Examples of Muscle Activity

Muscle action around the shoulder can easily be observed on yourself. The action of the trapezius
can be felt while shrugging the shoulders.

During pull-ups the arm is being extended and adducted on the body. The action of pectoralis
major and the latissimus dorsi is easily observed.

The main abductor of the glenohumeral joint is deltoid. This action is used when putting the arm
into a jacket sleeve.