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Ball-and-socket synovial joint — the most mobile joint in the body.
Formed between the head of humerus and the glenoid cavity of scapula.
Head of humerus: Large, hemispherical, directed medially, upwards, and backwards.
Glenoid cavity of scapula: Small, shallow, directed laterally, upwards, and forwards.
Glenoid labrum:
Fibrocartilaginous rim deepening the cavity.
Increases articular surface area and provides stability.
Attached to:
Medially: Margin of glenoid cavity beyond labrum.
Laterally: Anatomical neck of humerus (except inferiorly – surgical neck).
Loose and large → allows wide range of motion but less stability.
Strengthened by tendons and ligaments.
| Ligament | Attachments | Function |
|---|---|---|
| Capsular ligament | Surrounds joint | Permits free movement |
| Coracohumeral ligament | From base of coracoid process → greater tubercle | Strengthens capsule superiorly |
| Glenohumeral ligaments (3) | From glenoid margin → lesser tubercle | Reinforce capsule anteriorly |
| Transverse humeral ligament | Across intertubercular groove | Holds long head of biceps tendon in place |
| Coracoacromial ligament | Between coracoid and acromion forming coracoacromial arch | Prevents upward dislocation |
Subscapular bursa → communicates with joint cavity anteriorly.
Subacromial (subdeltoid) bursa → between supraspinatus tendon and acromion/deltoid; does not communicate with joint cavity.
Anterior: Subscapularis, coracobrachialis, short head of biceps.
Posterior: Infraspinatus, teres minor, posterior part of deltoid.
Superior: Coracoacromial arch and supraspinatus tendon.
Inferior: Long head of triceps and axillary nerve.
Axillary nerve (C5, C6)
Suprascapular nerve (C5, C6)
Lateral pectoral nerve
Anterior and posterior circumflex humeral arteries
Suprascapular artery
Rotator cuff muscles — Supraspinatus, Infraspinatus, Teres minor, Subscapularis (SITS).
Coracoacromial arch — prevents superior displacement.
Long head of biceps — acts as intra-articular stabilizer.
Glenoid labrum — deepens the socket.
Negative intra-articular pressure — suction effect.
Flexion/Extension → Transverse axis
Abduction/Adduction → Anteroposterior axis
Medial/Lateral rotation → Vertical axis
Circumduction → Combination of all above
Range: 0–180° (forward movement).
Muscles: Pectoralis major (clavicular head), Anterior deltoid, Coracobrachialis, Biceps brachii (short head).
Range: Up to 60°.
Muscles: Latissimus dorsi, Posterior deltoid, Teres major, Triceps (long head).
Range: 0–180° (combination with scapular movement).
0–15°: Supraspinatus (initiator)
15–90°: Deltoid (chief abductor)
90–180°: Serratus anterior + Trapezius (upward rotation of scapula)
Clinical: Supraspinatus test → empty can test positive in supraspinatus tear.
Muscles: Pectoralis major, Latissimus dorsi, Teres major, Subscapularis, Coracobrachialis.
Muscles: Subscapularis, Pectoralis major, Latissimus dorsi, Teres major, Anterior deltoid.
Muscles: Infraspinatus (chief), Teres minor, Posterior deltoid.
A combination of flexion, extension, abduction, and adduction → conical motion of limb.
For every 2° of glenohumeral movement, there is 1° of scapular rotation.
Total abduction of 180° = 120° at glenohumeral + 60° at scapulothoracic joint.
Place the cadaver supine; abduct and laterally rotate the upper limb.
Identify and clean deltoid muscle, then reflect it from clavicle, acromion, and spine of scapula.
Expose the coracoacromial arch, supraspinatus, and capsule beneath.
Identify supraspinatus, infraspinatus, teres minor, and subscapularis tendons forming the rotator cuff.
Trace the long head of biceps tendon as it passes within the capsule (in bicipital groove under transverse ligament).
Carefully incise the capsule to observe:
Head of humerus
Glenoid cavity and labrum
Subscapular recess anteriorly.
Move the humerus to demonstrate flexion, abduction, rotation, and circumduction.
Most common joint dislocation in body.
Direction: Usually anteroinferior due to weak inferior capsule.
Cause: Fall or forceful abduction & external rotation.
Clinical: Flattened shoulder contour, prominent acromion, humeral head palpable anteriorly.
Due to torn capsule or labrum.
Common in athletes and throwers.
Commonly involves supraspinatus tendon (degenerative or traumatic).
Presents with painful arc syndrome (pain during 60°–120° abduction).
Inflammation of subacromial bursa → pain during abduction.
May result from repetitive overhead activity.
Chronic inflammation and fibrosis of capsule → restricted all-directional movement.
Common in diabetics and post-injury.
May occur with surgical neck fracture or dislocation.
Causes deltoid paralysis, loss of shoulder contour, and sensory loss over regimental badge area.
Compression of supraspinatus tendon under coracoacromial arch.
Pain during abduction, positive Neer’s test.
Inflammation of long head of biceps tendon in intertubercular groove.
Causes anterior shoulder pain during flexion and supination.
Due to rupture of transverse humeral ligament, tendon slips medially over lesser tubercle.
Pain during 60°–120° abduction → indicates supraspinatus or subacromial pathology.
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