Introduction
- Type: Synovial
ball and socket joint
- Most mobile
joint in the body
- Formed
between the head of humerus and the glenoid cavity of scapula
- Allows
wide range of movement but less stable
Articular Surfaces
- Head of
humerus (large, round)
- Glenoid
cavity of scapula (shallow, small)
- Glenoid
labrum: fibrocartilage ring that deepens the socket
Ligaments
- Capsular
ligament – surrounds the joint
- Glenohumeral
ligaments – reinforce anterior side (superior, middle, inferior)
- Coracohumeral
ligament – from coracoid to humerus
- Transverse
humeral ligament – holds biceps tendon in place
- Coracoacromial
arch – roof of the joint
Relations
Anterior:
- Subscapularis
muscle
- Brachial
plexus (cords)
- Axillary
vessels
Posterior:
- Infraspinatus
& teres minor muscles
Lateral:
- Deltoid
muscle
Medial:
- Thoracic
wall
- Serratus
anterior muscle
Superior:
- Coracoacromial
arch
- Supraspinatus
muscle
Inferior:
- Long head
of triceps
- Axillary
nerve and posterior circumflex humeral vessels (important in injury)
Blood Supply
- Anterior
and posterior circumflex humeral arteries (branches
of axillary artery)
- Suprascapular
artery
Nerve Supply
- Axillary
nerve (main)
- Also by:
suprascapular nerve, lateral pectoral nerve
Movements at Shoulder
Joint
Performed by various muscles, mainly from rotator cuff and deltoid
|
Movement |
Muscles Involved |
|
Flexion |
Deltoid (anterior), pectoralis major |
|
Extension |
Deltoid (posterior), latissimus dorsi |
|
Abduction |
Supraspinatus (starts), deltoid (continues) |
|
Adduction |
Pectoralis major, latissimus dorsi |
|
Medial Rotation |
Subscapularis, pectoralis major |
|
Lateral Rotation |
Infraspinatus, teres minor |
|
Circumduction |
Combination of all movements |
Clinical Anatomy
- Dislocation: Most
common dislocated joint (usually anterior-inferior)
- Rotator
cuff injury: Supraspinatus tendon tear is common
- Frozen
shoulder (adhesive capsulitis): Painful stiffness
- Axillary
nerve injury: Causes deltoid muscle weakness and sensory loss over shoulder
Tags
ANATOMY