Arthromechanics of the Pectoral Girdle

Question 1

Bone movements during elevation

Answer 1

Upward movement of lateral end of clavicle at AC joint

Upward movement of scapula

Downwards glide of medial end of clavicle at SC joint

Forwards role of clavicle at SC joint

Question 2

Bone movements during depression

Answer 2

Downwards movement of lateral end of clavicle at AC joint

Downwards movement of scapula

Upward glide of medial end of clavicle at SC joint

Backwards role of clavicle at SC joint

Question 3

Bone movements during retraction

Answer 3

Backwards movement of lateral end of clavicle at AC joint

Backwards movement of scapula around the chest wall

Medial end of clavicle glides backwards at SC joint (due to concave convex rule - clavicle is concave AP)

Backwards roll of clavicle at SC joint

Question 4

Bone movements during Protraction

Answer 4

Forwards movement of lateral end of clavicle at AC joint

Forwards movement of scapula

Medial end of clavicle glides forwards at SC joint

Forwards roll of clavicle at SC joint

Question 5

Limiting factors for elevation

Answer 5

SCJ: Tension in costoclavicular ligs & subclavius

ACJ: Coracoclavicular lig
both bands

Question 6

Limiting factors for depression

Answer 6

SCJ: Interclavicular lig. &

intra-articular disc

Question 7

Limiting factors for protraction

Answer 7

CJ: Sternoclavicular ligament & costoclavicular ligament
ACJ: Coracoclavicular ligament & fibrous capsule

Question 8

Limiting factors for retraction

Answer 8

SCJ: Sternoclavicular ligament & costoclavicular ligament
ACJ: Coracoclavicular ligament & fibrous capsule

Question 9

What is the third degree of movement in the pectoral girdle and how does it occur?

Answer 9

Backwards rotation of the clavicle along its axis (axial rotation), as a result of movement at the GH joint

Question 10

What is the fulcrum?

Answer 10

The pivot point for movement - the costoclavicular ligament - since this is medial, small movement at medial end means large movement at lateral end