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Shoulder Joint (Glenohumeral Joint)



  1. This is ball and socket joint between head of humerus (ball) and glenoid cavity of scapula (socket). It is a multi-axial joint and enjoys considerable range of movements at the cost of stability. This joint is weak because the head of humerus is 3-4 times larger than the shallow glenoid fossa.
  2. Stability to shoulder joint is provided by :-
    1. Rotator cuff (musculotendinous cuff):- It is formed by blending of tendons of supraspinatus (superiorly), infraspinatusand teres minor (posteriorly), and subscapularis(anteriorly). Inferiorly, capsule is loose and lax and the joint is least protected here, as there is only one muscle crossing the joint inferiorly, i.e. long head of triceps.
    2. Tendon of long head of biceps passing above the head of humerusintracapsularly prevents upward displacement.
    3. Coracoacromial arch formed by coracoacromialligament connecting coracoid and acromian processes with each
    4. other protects the joint from above.

Bursae around the joints

There are following bursae around the shoulder:-

  1. Subacromial/subdeltoidbursa: - These are usually continuous with each other. It is one of the largest bursa of body. It separates coracoacromial arch and deltoid muscle from supraspinatus tendon and joint capsule. This bursa facilitates abduction and during this movement it moves beneath the acromion process. In subacromeal bursitis, pain is elicited when the deltoid is pressed just below the acromian process, the arm being in adducted position. When the arm is abducted to 90° pain cannot be elicited by pressure on the same point because bursa disappears under the acromian. This is called Dawbarn's sign.       
  2. Subscapular bursa: - It lies between anterior capsule and subscapularis muscle. It is always in continuity with the joint cavity.
  3. Infraspinatusbursa: - It lies between posterior capsule and infraspinatus tendon. Sometimes, it may communicate with joint cavity.

Movements around the shoulder joints

Active movements permitted at shoulder joint are: flexion and extension, abduction and adduction, circumduction, medial (internal) and lateral (external) rotation. The movements are analysed with reference to the body of scapula, unlike conventional plane of trunk. The flexion and extension take place at right angles to the plane of the body of scapula. Abduction and adduction take place parallel to the plane of the body of scapula.


Muscles producing movements


Main muscles

Accessory muscles





i) Clavicular head of pectoralis major
ii) Anterior fibers of deltoid


i) Corachobrachialis

ii) Short head of biceps

iii) Sternocostal head of pectoralis major




i) Posterior fibres of deltoid
ii) Latissimus dorsi

i) Teres major

ii) Long head of triceps




i) Pectoralis major

ii) Latissimus dorsi



i) Teres major

ii) Corachobrachialis

iii) Short head of biceps

iv) Long head of triceps





i) DeItoid(middle or acromial fibers)

ii) Supraspinatus

iii) Serratusanterior

iv) Upper and lower fibers of trapezius


Medial rotation



i) Pectoralis major

ii) Anterior fibers of deltoid
iii) Latissimus dorsi

iv) Teres major

i) Subscapularis


Lateral rotation


i) Posterior fibers of deltoid

ii) Infraspinatus

iii) Teres minor


Scapular-humeral mechanism

  1. Movement at shoulder joint occurs not only at glenohumeral joint, but is also contributed by rotation of scapula on thoracic wall. In abduction, out of total 1800 elevation, humerus moves 1200 at the shoulder joint and the remaining 600 is done by rotation of scapula. In every 15° elevation, shoulder joint contributes 100 and scapular rotation 5°, in the ratio of 2:1. Rotation of scapula is facilitated by movements at sternoclavicularandacromioclavicular joints. In higher ranges of abduction there is lateral rotation of humerus. Lateral rotation of scapularincreases the range of humeral elevation.
  2. Abduction is initiated by supraspinatus, which is responsible abduction upto 150. After that deltoid (acromial or middle fibers) is the major abductor up to 90° of abduction. These two muscles, supraspinatus and deltoid are the prime movers for abduction. Overhead abduction (>90°) is caused by trapezius and serratus anterior, which act by causing upward rotation of glenoid cavity.
    1. Painful arc syndrome is characterized by pain during mid-range of abduction (600 to 1200) with freedom from pain during the initial and terminal stages. This can be produced by (i) minor (partial) tear of supraspinatus; (ii) supraspinatus tendon inflammatory degeneration (supraspinatus tendinitis); (iii) calcific deposits in supraspinatus tendon; (iv) sub acromial bursitis; and (v) Greater tuberosity fracture.
    2. Shoulder joint is the commonest joint in human body to dislocate. Anterior dislocation is most common.

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