Module 8: Biomechanics & Control of the Upper Extremity

Question 1

Name the bones that form the upper extremity (shoulder girdle and limb).

Answer 1

Clavicle, scapula, humerus, ulna, radius, metacarpals, phalanges

Question 2

What is the function of the shoulder girdle?

Answer 2

Provide stability to allow function of the upper limb. Must provide extensive stability proximally to allow for function distally.

Question 3

Name the joints of the shoulder girdle.

Answer 3

Sternoclavicular joint, Acromioclavicular joint, Glenohumeral joint, Scapulothoracic joint

Question 4

What is the definition of dynamic stability?

Answer 4

Structures are constantly adjusting to provide a stable base so the limb can work and concurrently provide the power and coordination required for the task.

Question 5

What is rotator cuff and what is its main function?

Answer 5

A group of four muscles and their tendons that surround the shoulder joint, providing dynamic stability to the GH joint. They stabilize the GH joint during movement, ensuring the head of the humerus stays properly aligned in the glenoid cavity.

Question 6

What are the muscles that form the rotator cuff?

Answer 6

Supraspinatus, infraspinatus, teres minor, subscapularis

Question 7

What are the functions of the labrum in the glenohumeral joint?

Answer 7

Increase the depth (congruency) of the glenoid cavity

Question 8

What is the effect of gravity on the upper extremity?

Answer 8

Gravity pulls down on the humeral head when upright, continuous muscle action is required for coaptation (adaptation or adjustment) of the joint

Question 9

What is the definition of scapulohumeral rhythm?

Answer 9

The coordinated activity of muscles acting on the scapula and the glenohumeral joint (what the scapula is doing while the humerus is going through ROM). The combined coordinated activity of the scapular muscles and the rotator cuff muscles as they work together with deltoid and latissimus dorsi

Question 10

Which muscle initiates shoulder abduction?

Answer 10

Supraspinatus

Question 11

What is the relationship of shoulder movement and scapular movement during normal movement of abduction?

Answer 11

As the arm lifts, the scapula tilts, elevates, and rotates to maintain alignment. This coordination isn’t constant throughout the range of motion, but it ensures smooth movement. Disruption in this rhythm can lead to shoulder problems, and symmetry between both sides is typically expected.

Question 12

What is the region of the shoulder that is most susceptible to injury and why? Name 2 injuries that may occur in this area.

Answer 12

The rotator cuff due to its role in stabilizing the joint during movement, while being subjected to significant stress. The tendons in this area are prone to overuse and degenerative changes, especially in repetitive or overhead activities.
Rotator cuff tear – a partial or complete tear of one or more of the rotator cuff tendons, often due to overuse or trauma.
Impingement syndrome – when the rotator cuff tendons are compressed against the bony structures of the shoulder, leading to pain and inflammation.

Question 13

What is the role of supraspinatus muscle and other muscles of the rotator cuff during the movement of shoulder abduction?

Answer 13

The supraspinatus muscle is a major stabilizing force of the GH joint and is a dynamic stabilizer. It plays a key role in initiating shoulder abduction by lifting the arm for the first 15-30 degrees of the movement. Afterwards, the deltoid muscle takes over as the primary mover.

The other rotator cuff muscles (infraspinatus, teres minor, and subscapularis) contribute by stabilizing the humeral head in the glenoid cavity during abduction. They work together to prevent upward displacement of the humerus, ensuring smooth and coordinated movement while allowing the deltoid to function effectively.

Question 14

What accessory movement occurs in the glenohumeral joint during the movement of shoulder abduction?

Answer 14

Inferior glide: As the humerus abducts, the head of the humerus passively glides downward (inferiorly) to maintain contact with the glenoid cavity and prevent impingement.

Question 15

Name the movements, planes and axis of movement that are possible in the shoulder joint.

Answer 15

• Movement: Abduction and Adduction
  o Plane: Frontal
  o Axis: Anteroposterior
  *Movement: Flexion and Extension
  o Plane: Sagittal
  o Axis: Frontal (Mediolateral)
  *Movement: Internal and External Rotation
  o Plane: Transverse
  o Axis: Vertical (Longitudinal)
  *Movement: Circumduction: A circular movement that combines flexion, extension, abduction, and adduction, allowing the arm to move in a cone-like motion
   Plane: Involves all planes
   Axis: Involves all axes

Question 16

Name the movements, planes and axis of movement that are possible in the elbow joint.

Answer 16

• Movement: Flexion and extension
  o Plane: Sagittal plane
  o Axis: Frontal
• Movement: Pronation and supination
  o Plane: Transverse
  o Axis: Vertical

Question 17

Name 3 muscles that can act as elbow flexors

Answer 17

Biceps brachii, brachialis, brachioradialis

Question 18

Which of the 3 muscles that act as elbow flexors have better mechanical advantage when the forearm is supinated and why?

Answer 18

Biceps brachii:
* Optimal Length-Tension Relationship: Supination allows the biceps to generate force more effectively.
* Improved Line of Action: The alignment of the biceps with the forearm enhances force application at the elbow joint.
* Isolation of Function: Supination isolates the biceps’ role, maximizing its effectiveness as a flexor.

Question 19

Name the carpal bones

Answer 19

Scaphoid, lunate, triquetrum, pisiform, trapezoid, trapezium, capitate, hamate

Question 20

Name the movements, planes and axis of movement that are possible in the wrist

Answer 20

Flexion/extension – frontal plane - anteroposterior axis
Abduction/adduction – sagittal plane – frontal axis

Question 21

List 4 main functions of the hand.

Answer 21

Movement, Function, Sensation / discrimination, Coordination / dexterity

Question 22

Describe the anatomical configuration of hook grip

Answer 22

Involves all fingers flexed towards the palm, wrapping around an object like a handle, while the thumb remains inactive. This grip is commonly used when lifting heavy objects, like a suitcase

Question 23

Describe the anatomical configuration of a power grip

Answer 23

Features a strongly flexed thumb, with fingers flexed towards the thenar eminence (base of the thumb) and slightly ulnar deviated. The thumb, along with the ring and little fingers, provides the most force. This grip is commonly used in activities requiring power and stability, like a hammer.

Question 24

Describe the anatomical configuration of a key grip

Answer 24

Involves an extended thumb positioned on the radial side of the index finger. Used for holding keys or small objects

Question 25

Describe the anatomical configuration of pinch grip.

Answer 25

Involves the thumb contacting the fingertips, achieving tip-to-tip approximation. This configuration requires the fingers to rotate and ulnar deviate, allowing for a secure grasp of small objects, like a pen.

Question 26

What is the difference between open and closed kinetic chain?

Answer 26

They differ primarily in the relationship between the distal and proximal segments during movement.

OKC - The distal segment is free to move while the proximal segment remains fixed. In a bicep curl, the arm moves through space while the elbow is fixed.

CKC - The distal segment is fixed, and the proximal segment moves. In a push-up, the hands remain on the ground while the body moves

Question 27

Describe 2 strengthening exercises for the biceps brachii muscle in closed kinetic chain and 1 exercise for the same muscle in open kinetic chain.

Answer 27

CKC – Push up and chin up
OKC – Bicep curl

Question 28

What is the role of the negative intrarticular pressure of the glenohumeral joint?

Answer 28

Contributes minimally to joint stability. It increases with downward loads on the arm, helping to prevent further downward glide of the humeral head. During abduction, this negative pressure provides additional inferior stability to the humeral head.

Question 29

What is the most superficial nerve of the elbow joint?

Answer 29

Radial nerve

Question 30

What is the definition of proprioception?

Answer 30

The sense that allows individuals to perceive the position and movement of their body parts in space.

Question 31

What is the neutral position of the wrist?

Answer 31

The wrist is straight, neither flexed nor extended, and the hand is relaxed with fingers slightly extended. This position promotes stability and minimizes strain. Think of a hand splint.