Biomechanics of the Elbow Flashcards
Biomechanics
Which two joints in the arm allow for elbow flexion?
Elbow
The humeroulnar and humeroradial joints.
Biomechanics
Which three joints in the arm allow forearm pronation and supination.
Elbow
- Humeroradial Joint
- Proximal Radioulnar Joint
- Distal Radioulnar Joints
Biomechanics
The humeroulnar joint is an articulation between what two structures?
Elbow
The Trochlea (Humerus) and the Trochelar Notch (Ulna)
Biomechanics
Is the trochlea symmetrical along its medio-lateral axis? What does this cause?
Elbow
No, there is distal prolongation of the medial lip of the trochlea. The asymmetry causes the ulna to deviate laterally producing a valgus carrying angle.
Biomechanics
What is the normal carrying angle for the elbow ?
Elbow
13° +/- 6° of lateral deviation
Biomechanics
Excessive cubitus valgus may overstretch and damage which nerve?
Elbow
The ulnar nerve at the cubital tunnel.
Biomechanics
Medial collateral ligament consists of ____, ____, and ____ fiber bundles.
Elbow
Anterior
Posterior
Transverse
Biomechanics
Which fibers of the medial collateral ligament are the strongest?
Elbow
Anterior
Biomechanics
Where do the anterior fibers of the medial collateral ligament originate and insert?
Elbow
They arise from anterior part of medial epicondyle and insert on medial part of coronoid process of ulna
Biomechanics
Where do the posterior fibers of the medial collateral ligament originate and insert?
Elbow
They originate on the posterior part of medial epicondyle and insert on medial margin of olecranon process
Biomechanics
Where do the transverse fibers of the medial collateral ligament originate and insert?
Elbow
From olecranon to coronoid process of ulna
They do not provide significant articular stability because they originate and insert on the same bone
Biomechanics
In addition to MCL, the proximal fibers of what groups of muscles resist excessive valgus-producing strain at elbow?
Elbow
The proximal fibers of wrist flexor and pronator group of muscles (especially the flexor carpi ulnaris)
Biomechanics
Where does the radial collateral ligament run and what motion does it oppose?
Elbow
From the lateral epicondyle to the annular ligament. It opposes varus stress.
Biomechanics
The humeroulnar joint can be distracted at a ____ angulation to the ulna and mediolaterally glided at a ____ angulation to a line between the epicondyles?
Elbow
45° | 60°
Biomechanics
The humeroradial joint is an articulation between what two structures?
Elbow
The Capitulum (Humerus) and the Radial Head (Radius)
Biomechanics
What motion synkinetically pairs with elbow extension?
(Pronation or Supination)
Elbow
Pronation
Biomechanics
At the proximal radioulnar joint the radius is con- ____ and the ulna is con- ____ .
Elbow
Radius: Convex
Ulna: Concave
Biomechanics
At the distal radioulnar joint the radius is con- ____ and the ulna is con- ____ .
Elbow
Radius: Concave
Ulna: Convex
Biomechanics
A posterior glide of the proximal radius promotes which two elbow motions?
Elbow
Extension and Pronation
Biomechanics
Describe the arthrokinematics of pronation and supination at the distal radioulnar joint.
Elbow
Pronation: palmar roll, palmar glide
Supination: dorsal roll, dorsal glide
Biomechanics
What four muscles flex the elbow?
Elbow
Biceps Brachii (Also Supinates)
Brachialis (Strongest)
Brachioradialis
Pronator Teres
Biomechanics
What two muscles extend the elbow?
Elbow
- Triceps Brachii
- Anconeus
Biomechanics
What two muscles supinate the arm?
Elbow
- Biceps Brachii
- Supinator
Biomechanics
What two muscles pronate the arm?
Elbow
- Pronator Teres
- Pronator Quadratus
Biomechanics
Which positions make the biceps active and passively insufficient ?
Elbow
Active: shoulder flexion and elbow flexion
Passive: shoulder and elbow extension
