Elbow And Forearm Biomechanics

Question 1

What type of joint is the elbow ?

Answer 1

Hint joint

Question 2

Name the static stabilizers of the elbow joint and their functions

Answer 2

Medial collateral ligaments

• anterior fibers : resist valgus, limits flexion and extension
• posterior fibers : resist valgus and limit flexion
• transverse fibers

Lateral collateral ligaments

• radial collateral ligament : resists varus
• ulnar collateral ligament : resists varus, external rotation of elbow complex and flexion
• annular ligament : avoids distraction of the radius

Question 3

Name the dynamic stabilizers of the elbow complex

Answer 3

• flexor carpi radialis
• flexor carpi ulnaris
• pronator teres
• supinator
• extensor carpi radialis brevis

Question 4

What is the ROM of elbow flexion ?

Answer 4

• flexion varies with the contact to soft tissues but usually up to 140°-150°
• extension is 0° but some degrees of hyper extension are possible : from 10° to 15°

All together : functional ROM

Question 5

Describe the arthrokinematics of elbow flexion / extension

Answer 5

The concave trochlear notch and fovea of radius roll and slide in the same direction as the movement.

Question 6

Name the agonists of elbow flexion

Answer 6

1) biceps brachi
2) brachoradialis
3) coracobrachialis

Question 7

Name the synergists of elbow flexion

Answer 7

1) flexor carpi radialis
2) flexor carpi ulnaris
3) palmaris longus
4) pronator teres
5) extensor carpi radialis longus
6) extensor carpi radialis brevis

Question 8

What is special about annular ligament ?

Answer 8

It is lined by cartilage

Question 9

What is special about distal radio-ulnar joint ?

Answer 9

There is a disc

Question 10

Name the stabilizers of the distal radio ulnar joint

Answer 10

• triangular fibrocartilage complex
• pronator quadratus
• tendon of extensor carpi ulnaris
• distal oblique fibers of the interosseous membrane

Question 11

Give 5 features of the interosseous membrane

Answer 11

• bound together the radius and the ulna
• is directed distal to medial from the radius connected to the ulna at about 20°
• central band has a tensile force similar to the one of patellar tendon
• serves as an attachement for extrinsic muscles of the hand
• transmit forces from the radius to the ulna

Question 12

What are the ROM of pronation and supination

Answer 12

Pronation : 75°

Supination : 85°

Question 13

Describe the arthrokinematics of forearm supination / pronation

Answer 13

The concave radius slide on the convex ulna in the same direction as the movement

Question 14

What happens to proximal end of the radius during pronation and supination

Answer 14

• it rotates at both the proximal radio ulnar joint and humero radial joint

Question 15

How can the hand have a ROM of nearly 360° ?

Answer 15

Pronation and supination are combined with shoulder internal and external rotation

Question 16

Name the agonists of forearm supination

Answer 16

1) biceps brachi

2) supinator

Question 17

Name the synergists of forearm supination

Answer 17

1) brachoradialis

Question 18

Name the agonists of forearm pronation

Answer 18

1) pronator teres

2) pronator quadratus

Question 19

Name the synergists of forearm pronation

Answer 19

1) brachioradialis