Stay Apparatus

Question 1

Functions

Answer 1

1. Sleeping while standing (non-R.E.M.)

2. Reduce stress on distal limb during high speed gaits

Question 2

What Muscle must contract to initiate the stay apparatus, then relaxes?

Answer 2

Triceps brachial

Question 3

What four joints are involved in the forelimb stay apparatus?

Answer 3

1. Shoulder
2. Carpus
3. Fetlock
4. Pastern

Question 4

Shoulder

Answer 4

COG behind joint - must prevent flexion

• internal biceps tendon, originating from the supraglenoid tubercle of the scapula, connects with the extensor carpi radialis tendon via the lacterus fibrosis (ECR inserts on the metacarpal tuberosty of MC3)
• creates connected from scapula to MC3
• when limb is weight bearing, tension from ECR is transferred to internal biceps tendon, preventing shoulder flexion

Question 5

Carpus

Answer 5

COG in front of joint - must prevent overextension

• dorsally flattened articulate surfaces of carpal bones
• palmar carpal ligament
• digital flexor tendons & their check ligaments (DFs stabilize joint, check ligs protect the tendons from damage when being stretched)
• upward pull of ECR tendon prevents buckling

Question 6

Fetlock

Answer 6

COG in front of joint - must prevent overextension

• suspensory apparatus: interosseus, proximal sesamoid bones, and all sesamoidean ligaments
• straight sesamoidean lig = most important because of its fibrocartilaginous attachment to P2 (lig crosses pastern)
• digital flexor tendons also help prevent overextension because they pass on palmar side of joint to stabilize

Question 7

Pastern

Answer 7

COG in front of joint - prevent overextension

• Palmar ligaments, straight sesamoidean ligament, and DDF tendon
• SDF tendon prevents bucking

Question 8

What factors help the coffin joint to land square on the ground (prevent toeing through hoof)?

Answer 8

1. Interdigitation of lamina

2. Extensor branches of interosseus