Elbow Biomechanics

Question 1

Humero-Ulnar Joint

Answer 1

Adjusts functional length of limb

Question 2

Radio-Ulnar Joint

Answer 2

Adds considerable versatility to hand placement

Question 3

Valgus Angle at the Elbow

Answer 3

The medial lateral axis of rotation is angled slightly superior due to the shape of the trochlea

Normal: 13 degrees +/- 6 degrees
Excessive: >20 degrees (stresses medial structures)
Decreased: < 7 degrees

Question 4

Primary Motions/Arthokinematics of Humero-Ulnar Joint

Answer 4

Flexion and Extension
Roll and slide in same direction

Question 5

Supination

Answer 5

The radius and ulna are positioned parallel and the palm faces forward
Roll and slide of Radius
Rotation of the Redial head on the Capitulum

Question 6

Pronation

Answer 6

The radius crosses the ulna and the palm faces backward
Roll and slide of Radius
Rotation of the Redial head on the Capitulum

Pronator teres resultant vector pulls radial head into capitulum

Question 7

Elbow ROM

Answer 7

Normal: 145 - (-5) degrees
Functional: 130 - 30 degrees

Loss of elbow flexion affects reaching ability

Question 8

Normal Forearm Pronation and Supination

Answer 8

Supination
Normal: 85 degrees
Functional: 50 degrees

Pronation:
Normal: 75 degrees
Functional: 50 degrees

Question 9

Elbow Flexor Torque-Generating Capacity

Answer 9

Flexor torque is approximately 25% greater with the forearm in supination than in pronation

Greatest torque/strength is at 85-90 degrees

Question 10

Elbow Flexor Moment Arm Lengths

Answer 10

The combination of the greatest moment arm lengths occurs at approximately 100°