The shoulder joint is a complex joint system with high mobility but low stability. It consists of the glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic joints. The glenohumeral joint is a ball and socket synovial joint between the humeral head and glenoid cavity that allows mobility through surrounding muscles and soft tissues. The glenoid labrum deepens the cavity and protects the bone. Rotator cuff muscles including supraspinatus, infraspinatus, teres minor, and subscapularis provide dynamic stability and allow movements like flexion, extension, abduction, and rotation.

1. THE SHOULDER JOINT:
ANATOMY AND BIOMECHANICS
PRESENTER: DR KAUSTAV BASU THAKUR
MODERATOR: PROF. YUMNAM NANDABIR SINGH

2. INTRODUCTION
 THE SHOULDER COMPLEX
 Complicated joint complex
 High degree of mobility compromising stability
 Involved in a variety of overhead activities
 Consists of
 Acromioclavicular Joint
 Sternoclavicular Joint
 Scapulothoracic joint
 Glenohumeral joint

3. BONY ANATOMY

4. GLENOHUMERAL JOINT
 Most commonly dislocated joint
 Synovial multiaxial “ball & socket” joint
 Between head of humerus and glenoid cavity of scapula
 Accommodates one third of the humerus head
 Mobility gained at the expense of stability
 Stability depends on the surrounding muscular and soft tissue

5. GLENOID LABRUM
 Fibrocartilaginous rim
 Triangular in section
 Base attached to margin
of the fossa
 Free inner edge as
continuation of curve of
glenoid cavity

6. GLENOID LABRUM CONTD..
 FUNCTION
 Deepens the glenoid cavity
 Protects the edges of bone
 Acts as a lubricant

7. ARTICULATING SURFACES
 Reciprocally curved and ovoids
 The area of the humeral convexity exceeds that of the glenoid concavity
 Remaining articular surface in contact with the capsule and contact on
glenoid fossa is more uniformly distributed over its entire articular surface
 Articular surfaces covered by hyaline cartilage
 thickest centrally, thinner peripherally over the humerus and the
reverse in the glenoid cavity

8. ARTICULATING SURFACES CONTD.

9. MOBILITY AND STABILITY
Factors contributing to mobility
 Type of joint – Ball and socket
 Bony surfaces – Shallow glenoid cavity and large humeral
head
 Laxity of the joint capsule

10. MOBILITY AND STABILITY CONTD
Factors contributing to stability
 Rotator cuff muscles
 Surround the shoulder joint
 Attached to the tubercles of the humerus and joint capsule
 Resting tone act to ‘pull’ the humeral head into the glenoid cavity
 Glenoid labrum
 Ligaments – The ligaments act to reinforce the joint capsule and forms
the coraco-acromial arch

11. FIBROUS CAPSULE
 Encircles entire glenohumeral
joint
 Attachment:
 Scapular
 Humeral except
 Medially
 Anteriorly

12. MUSCLES SUPPORTING THE CAPSULE
Superiorly  Supraspinatus
Inferiorly  Long Head of
Triceps
Posteriorly  Tendons of
Infraspinatus and Teres Minor
Anteriorly  Tendon of
Subscapularis

13. OPENINGS IN THE FIBROUS CAPSULE
Posteriorly
Not constant where a
communication exists
between joint and a bursal
sac belonging to
Infraspinatus muscle
Anteriorly
Below coracoid Process
connection between synovial
membrane of the joint and a
bursa beneath the tendon of
subscapularis muscle
Between the 2 tuberosities
passage of the biceps long
head tendon

14. SYNOVIAL MEMBRANE
 Lines the inner surface of the
fibrous capsule
 At humerus covers the anatomical
neck upto margin of the articular
surface of humerus head and
medially a part of shaft below the
epiphyseal line
 At glenoid goes to margin and
covers both surfaces of glenoidal
labrum
 Communicates with subscapular
bursa or infraspinatus bursa

15. BURSA AROUND GH JOINT
1. Acromial: upper surface of
acromian process
2. Subacromial: inferiorly to the
deltoid and acromion
3. Subcoracoid bursa
4. Infraspinatus bursa
5. Subscapular bursa: between the
subscapularis tendon and
scapula

16. LIGAMENTS OF THE SHOULDER JOINT
 Act as static stabilisers
 Three in numbers
 Glenohumeral (superior,
middle and inferior)
 Coraco humeral
 Transverse humeral

17. GLENOHUMERAL LIGAMENT
Three fibrous bands derived from thickening
of the anterior part of fibrous capsule
All 3 Converge upward and medially blend
with glenoid labrum:
SUPERIOR BAND : attached to the upper
end of lesser tubercle
MIDDLE BAND : attached to lower part of
lesser tubercle
INFERIOR BAND : lower part of
anatomical neck of humerus

18. TRANSVERSE HUMERAL LIGAMENT
Broad band of fibrous
tissues
Connects the two lips of
the upper part of
intertubercular sulcus
Acts as a retinaculum to
keep the long tendon of
biceps in position

19. CORACO-HUMERAL LIGAMENT
Broad thick Band
Strengthens Upper part of
Capsular Ligament
Attachments
Arises from outer border of
coracoid process
Blended with tendon of
supraspinatus muscles
United to capsule in greater
part of its extend.

20. VASCULAR SUPPLY
 Supplied by branches from
 Anterior circumflex humeral
artery
 Posterior circumflex humeral
artery
 Suprascapular artery
 Circumflex scapular artery

21. NERVE SUPPLY
 Glenohumeral joint
 Posterior cord of the
brachial plexus
 Capsule
 Suprascapular nerve
(posterior and superior parts)
 Axillary nerve (antero
inferior)
 Lateral pectoral nerve (antero
superior)

22. MUSCLES AROUND SHOULDER JOINT
 Primary role
a. Movements of arm
b. Dynamic stabilisation of glenohumeral joint
 There are 14 muscles divided into 4 functional groups
1. Three heads deltoid (anterior, middle, posterior)
2. Four rotator cuff muscles and biceps muscle
3. Two axio humeral muscles(pectoralis major and latismus dorsi)
and teres major
4. Scapular muscle group –serratus anterior , trapezius, rhomboid
major and minor and levator scapulae

23. MUSCLES IN RELATION TO THE JOINT
 Above - Supraspinatus
 Below - Long head of Triceps
 Front - Subscapularis
 Behind - Infraspinatus and Teres
Minor
 Deltoid is placed most externally
and covers the articulation from its
outer side, as well as in front and
behind

24. MOVEMENTS AT THE SHOULDER JOINT
 Osteokinematics
Flexion
Extension
Abduction
Adduction
Internal rotation
External rotation
Horizontal abduction
Horizontal adduction
Circumduction

25. FLEXION
Plane of Motion:
Sagittal Plane
Axis of Motion:
Transverse Axis through the
center of the humeral head
Muscles Involved:
Pectoralis major
Anterior Fibres of Deltoid
Coracobrachialis
Biceps (when the forearm is
flexed)
Range of Motion
0 – 170 degrees

26. EXTENSION
 Plane of Motion:
Sagittal Plane
 Axis of Motion:
Transverse Axis through the
center of the humeral head
 Muscles Involve:
Latissimus dorsi
Teres major
Posterior fibers of Deltoid
Triceps (When forearm is
extended)
 Range of Motion
0 – 60 degrees

27. ABDUCTION
 Plane of Motion:
Frontal Plane
 Axis of Motion:
Sagittal axis through the centre of the
humeral head
 Muscles Involve:
Deltoid
Supraspinatus
 Range of Motion
Total : 0 – 170 degrees

28. ADDUCTION
 Plane of Motion:
Frontal Plane
 Axis of Motion:
Sagittal axis through the centre of the
humeral head
 Muscles Involve:
Subscapularis
Pectoralis Major
Latissimus dorsi
Teres major

29. INTERNAL ROTATION
 Plane of Motion:
Transverse Plane
 Axis of Motion:
Vertical axis through the centre of
humeral head
 Muscles Involve:
Subscapularis
Pectoralis Major
Latissimus dorsi
Teres major
 Range of Motion:
0-70º as the arm at 90º of shoulder
abduction and 90º elbow flexion
0-60° if abduction not possible

30. EXTERNAL ROTATION
 Plane of Motion:
Transverse Plane
 Axis of Motion:
Vertical axis through the center
of humeral head
 Muscles Involve:
Infraspinatus
Teres Minor
 Range of Motion
0-90º as the arm at 90º of
shoulder abduction and 90º
elbow flexion
0-80° if abduction not possible

31. CIRCUMDUCTION
 A combination of flexion, abduction, extension, and adduction or in the reverse
sequence.
 Occurs in a cone whose apex is the head of humerus
glenohumeral flexion  abduction  extension  adduction
glenohumeral extension  abduction  flexion  adduction

32. SCAPULOHUMERAL RHYTHM
 The first 30 degrees
 At gleno-humeral joint with slight movement of clavicle
 From 30 to 120 degrees
 1/3 of movement coming from scapula rotating on thorax
 From 120 to 180 degrees
 Movement mainly scapulo-thoracic
 Sterno-clavicular joint participates in movements close to the trunk
 Acromioclavicular joint moves in the last 60 degrees of abduction

33. ROTATOR CUFF
 Group of four muscles to hold the head of humerus into the glenoid fossa
 They are
Supraspinatus Infraspinatus
Teres Minor Subscapularis

34. FUNCTION OF ROTATOR CUFF
 Important in movements and maintaining joint stability
 Abduction: Concavity compression
 Rotator cuff muscles also perform
 Abduction
 Internal rotation
 External rotation of the shoulder

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