Joints of the Shoulder Girdle
The shoulder girdle has two important joints:
- 1. Sternoclavicular joint (SC joint)
- 2. Acromioclavicular joint (AC joint)
These allow the scapula and clavicle to move freely, giving the upper limb a wide range of mobility.
A. Sternoclavicular Joint
Type
- Synovial saddle joint (but functions like a ball-and-socket joint due to articular disc).
Articular Surfaces
- Medial end of clavicle (convex vertically, concave anteroposteriorly).
- Clavicular notch of manubrium sterni.
- First costal cartilage (forms part of articular surface).
Articular Disc
- Fibrocartilaginous, divides joint into two cavities.
- Functions:
- Increases stability.
- Absorbs shock (transmits forces from upper limb to axial skeleton).
- Allows different movements in each compartment.
Capsule
- Surrounds joint; attached to articular margins.
Ligaments
- 1. Anterior & Posterior Sternoclavicular ligaments – thicken capsule, prevent displacement.
- 2. Interclavicular ligament – connects both clavicles across jugular notch; resists depression.
- 3. Costoclavicular ligament – between clavicle & 1st rib cartilage; strongest ligament, limits elevation.
Relations
- Anterior: sternomastoid, skin.
- Posterior: great vessels (brachiocephalic vein), pleura.
Movements
- Elevation & depression of clavicle.
- Protraction & retraction of clavicle.
- Rotation of clavicle around its long axis.
These movements allow scapula rotation and shoulder movements.
Blood Supply
- Branches of internal thoracic & suprascapular arteries.
Nerve Supply
- Nerve to subclavius.
- Supraclavicular nerves.