Elbow Biomechanics Flashcards

1
Q

What joints make up the elbow (4)

A
  1. Humeroulnar
  2. Humeroradial
  3. Proximal radioulnar
  4. Distal radioulnar
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2
Q

What is the shape of the radial head

A

More oval than spherical

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3
Q

What are the points of articulation for the proximal radioulnar joint (2)

A
  1. Radial head

2. Radial notch of the ulna

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4
Q

What are the points of articulation for the distal radioulnat joint (2)

A
  1. Ulnar head

2. Ulnar notch of the radius

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5
Q

What does TFCC stand for

A

Triangular FibroCartilage Complex

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6
Q

What type of joint are the humeroulnar and humeroradial joints

A

Hinge joint, uniaxial diarthrodial

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7
Q

What motion occurs at the humeroulnar and humeroradial joints

A

Flexion and extension

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8
Q

What type of joint are the proximal and distal radioulnar joints

A

Pivot joint (trochoid joint), uniaxial diarthrodial

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9
Q

What motion occurs at the proximal and distal radioulnar joints

A

Supination and pronation

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10
Q

True or False:

The joint capsule of the elbow is fairly large, loose, and weak anteriorly and posteriorly

A

True

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11
Q

What are the sides of the capsule reinforced by

A

Ligaments

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12
Q

What joints does the capsule enclose (3)

A
  1. Humeroulnar
  2. Humeroradial
  3. Proximal radioulnar
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13
Q

Does the joint capsule enclosing 3 joints have any potential problems

A

Yes, there is the potential for cross contamination of infection

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14
Q

What are the ligaments of the elbow (4)

A
  1. Ulnar collateral ligament (medial)
  2. Radial collaterla ligament (lateral)
  3. Annular ligament
  4. Interosseous membrane
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15
Q

What are the 3 parts of the UCL

A
  1. Anterior
  2. Oblique
  3. Posterior
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16
Q

Where does the anterior UCL run

A

Medial epicondyle to coronoid process

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17
Q

What does the anterior UCL stabilize against

A

Valgus stress

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18
Q

When does the anterior UCL protects the best

A

20-120 of flexion

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19
Q

True or False:

We don’t need the anterior UCL to be effective at 0-20 due to the oleranon

A

True

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20
Q

Where does the posterior UCL run

A

Medial epicondyle to ulnar coronoid process and olecranon

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21
Q

What is the posterior UCL’s main function

A

Primary co-stabilizer against valgus stress at 120 flexion

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22
Q

What is the posterior UCL’s secondary function

A

Secondary stabilizer at 30 and 90 flexion (NOT A RANGE)

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23
Q

What are the other names for the oblique UCL

A

Transverse and Cooper’s

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24
Q

Where does the oblique UCL run

A

Olecranon and coronoid process

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25
Q

What is the function of the oblique UCL

A

Helps hold down the anterior and posterior UCL

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26
Q

What happens because the oblique UCL holds down the anterior and posterior UCL ligaments

A

The oblique UCL helps maintain joint surface approximation

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27
Q

Where does the RCL run

A

Inferior lateral epicondyle to annular ligament and olecranon

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28
Q

What does the RCL resist (2)

A
  1. Varus stress

2. Distractive forces of joint surfaces

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29
Q

What does the annular ligament do

A

Stabilizes head of radius to ulna`

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30
Q

What is it called when the radial head dislocates from the annular ligament

A

Nurse maids elbow

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31
Q

What is the shape of the annular ligament

A

Circular

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32
Q

Does the annular ligament and radial head have a perfect match

A

No

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33
Q

what is the interosseous membrane between

A

Radius and ulna

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34
Q

Which directions are the fibers of the interosseous membrane

A

Every direction

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35
Q

What does the fibers being in every direction do

A

Provides strength

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36
Q

What are the arthrokinematics of the humeroulnar and humeroradial joints

A

Concave on convex

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37
Q

What arthrokinematic motions occur with flexion and extension at the humeroulnar and humeroradial joints

A

Flexion: Anterior roll, Anterior glide
Extension: Posterior roll, Posterior glide

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38
Q

What are the arthokinematics of the proximal radioulnar joint

A

Spin of radial head on capitulum

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39
Q

Which way is the radial head longer when supinated

A

A-P

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40
Q

Which way is the radial head longer when pronated

A

M-L

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41
Q

What are the arthrokinematics of the distal radioulnar joint

A

Concave radius on convex ulna

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42
Q

What are the arthrokinematic motions of the distal radioulnar joint during pronation and supination

A

Pronation: Anterior roll, Anterior glide
Supination: Posterior roll, Posterior glide

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43
Q

Where is the axis of motion at the elbow joint

A

Fixed through the center of trochlea and capitulum

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44
Q

What projects more distal capitulum or trochlea

A

Trochlea

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45
Q

Is the axis of rotation at the elbow perfectly in the M-L axis

A

No

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46
Q

What is the average angle of the axis of rotation at the elbow

A

5-15

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47
Q

What is cubitus valgus

A

More than 15 carrying angle

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48
Q

What is cubitus varus

A

Less than 5 carrying angle

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49
Q

Who has a greater cubitus valgus males or females and why

A

Females due to the greater pelvic angle

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50
Q

What does cubitus mean

A

Elbow

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51
Q

What makes the carrying angle

A

The axis of motion at the elbow

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52
Q

How do you measure the carrying angle

A

Using the long axis of the humerus and ulna then take the angle made at the intersection of the lines

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53
Q

Why do you measure from the ulna and not center of the forearm

A

The ulna is fixed so the angle will not vary if measured from it

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54
Q

What is the normal carrying angle for men

A

5

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55
Q

What is the normal carrying angle for women

A

15

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56
Q

What motions cause the carrying angle to disappear

A

Pronation and full elbow flexion

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57
Q

Why does the carrying angle disappear with pronation and full elbow flexion

A

Change in the orientation of the forearm levers due to the radius gliding over the ulna

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58
Q

What is the open pack position

A

The position in which the joint capsule and ligaments have the greatest laxity

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59
Q

What is the close pack position

A

The position in which the joint capsule and ligaments are the most taut

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60
Q

True or False:

The close pack position is most often the position where the most joint congruency occurs

A

True

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61
Q

What is normal elbow extension

A

0

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62
Q

How much hyperextension can a person have that is not pathologic

A

10-15

63
Q

What is the end feel for elbow extension

A

Hard

64
Q

What is the close pack position of the humeroulnar joint

A

Full extension

65
Q

What is the open pack position of the humeroulnar joint

A

70 Flexion

66
Q

What is the close pack position of the humeroradial joint

A

90 Flexion

67
Q

What is the open pack position of the humeroradial joint

A

Full extension

68
Q

Why is the humeroradial joint in the open pack position during full extension

A

The radial head should not have any contact with the capitulum of the humerus

69
Q

What are the check reins to extension (3)

A
  1. Olecranon process/fossa
  2. Anterior capsule and anterior portion of collateral ligaments
  3. Flexor muscle tension
70
Q

What is normal AROM of elbow flexion

A

135-145

71
Q

What is normal PROM of elbow flexion

A

150

72
Q

What is the end feel for elbow flexion

A

Soft or hard

73
Q

What are the check reins to elbow flexion (3)

A
  1. Approximation of anterior musculature
  2. Bony articulation
  3. Passive stretch of triceps and posterior capsule
74
Q

When dos approximation of anterior musculature occur first pronation or supination

A

Pronation

75
Q

What are the primary movers of elbow flexion (3)

A
  1. Biceps brachii
  2. Brachioradialis
  3. Brachialis
76
Q

What are the secondary movers of elbow flexion (2)

A
  1. Pronator teres

2. Wrist flexors

77
Q

What determines the role of flexor muscles (6)

A
  1. Location of muscles
  2. Joint ROM
  3. Forearm position
  4. Magnitude of load applied
  5. Type of muscular contraction
  6. Velocity of movement
78
Q

What is a spurt muscle

A

Mobility muscle

79
Q

What type of muscle if the biceps brachii

A

Spurt muscle

80
Q

What does a spurt muscle have

A

Increased rotary component and angle of pull

81
Q

Where is the insertion of the muscle in relation to the axis of rotation

A

Close to the axis of rotation

82
Q

Where is the MA of the biceps brachii the greatest

A

80-100 of elbow flexion

83
Q

When is the biceps brachii most effective

A

Forearm supinated for power activities

84
Q

Is the biceps brachii effective during both concentric and eccentric contractions

A

Yes

85
Q

What type of muscle is the brachioradialis

A

Shunt muscle

86
Q

What is a shunt muscle

A

Stabilizing muscle

87
Q

Where is the insertion for a shunt muscle

A

Far from joint axis

88
Q

True or False:

Shunt muscles have a decreased rotary component and decreased angle of pull

A

True

89
Q

Does the shunt muscle increase or decrease compressive force

A

Increase

90
Q

Where is the moment arm of the brachioradialis greatest

A

Between 100 and 110 elbow flexion

91
Q

When is the brachioradialis most effective

A

Neutral forearm position

92
Q

True or False:

There is slightly less pronation than supination of the forearm

A

True

93
Q

What is the second most effective position of the brachioradialis

A

Full pronation because pronation is closer to neutral than supination

94
Q

What type of muscle is the brachialis

A

Spurt muscle

95
Q

What position is the brachialis most effective

A

All forearm positions

96
Q

What position isolates the brachioradialis

A

Pronation of forearm

97
Q

When is the moment arm of the brachialis grestest

A

100 elbow flexion

98
Q

The brachialis is consider what of forearm flexion

A

Work horse

99
Q

Which of the triceps muscles is a 2 joint muscle

A

Long head

100
Q

Which of the triceps muscles is consider to be the work horse of extension

A

The medial head

101
Q

What is the optimal length of the triceps muscles

A

30 elbow flexion

102
Q

True or False:

The triceps acts synergistically with biceps during resistive forearm supination

A

True

103
Q

How does the triceps act synergistically with the biceps during resistive forearm supination

A

Prevents flexion of forearm by isometrically contracting

104
Q

What is the main function of the anconeus

A

Initiate elbow extension

105
Q

How does the anconeus initiate elbow extension

A

Draws posterior capsule posteriorly to prevent impingement of capsule

106
Q

True or False:

The anconeus has attachment to the posterior capsule and annular ligament

A

True

107
Q

What is pronation of the forearm

A

85

108
Q

What is supination of the forearm

A

90

109
Q

What is the end feel of supination

A

Firm

110
Q

What is the end feel of pronation

A

Firm or hard

111
Q

What are the check reins to pronation of the forearm (4)

A
  1. Radius over ulna
  2. Posterior fibers of UCL
  3. Posterior radioulnar ligament
  4. Supinator
112
Q

What are the check reins to supination of the forearm (6)

A
  1. Anterior radioulnar ligament
  2. Oblique cord of UCL
  3. Pronator teres
  4. Pronator quadratus
  5. Interosseous membrane
  6. Annular ligament
113
Q

What is the open pack position of the proximal radioulnar joint

A

35 supination and 70 elbow flexion

114
Q

What is the closed pack position of the proximal radioulnar joint

A

5 supination and elbow extended

115
Q

What is the open pack position good for

A

Joint play, joint mobilizations, non thrust

116
Q

What is the close pack position good for

A

Stabilization via CKC

117
Q

True or False:
When a person is hypermobile we want them in the close pack position to promote osseous stability or capsuloligamentous intergrity

A

True

118
Q

What is osseous stability

A

Greater joint congruency

119
Q

What is the axis of rotation for the proximal and distal radioulnar joint

A

Longitudinal from radial head to ulnar head

120
Q

During supination what is the orientation of the radius and ulna

A

Parallel

121
Q

During pronation what is the orientation of the radius and ulna

A

Radius over ulna

122
Q

Which way does the ulnar head move during pronation

A

Slightly distal and dorsal

123
Q

Which way does the ulnar head move during supination

A

Slightly proximal and ventral

124
Q

What is the primary mover for supination

A

Biceps Brachii

125
Q

What is the secondary mover for supination

A

Supinator

126
Q

When is the biceps brachii active during supination

A

When resistance is met and with increased speeds

127
Q

Where is the biceps brachii most efficient

A

90 of elbow flexion

128
Q

How does the supinator act

A

By “unwinding” pulls shaft and distal end of radius off the ulna

129
Q

What angles is the supinator active in

A

All angles of elbow flexion

130
Q

What work synergistically to cause supination (4)

A
  1. Supinator
  2. Biceps brachii
  3. Triceps
  4. Anconeus
131
Q

What do the triceps and anconeus do for supination

A

Stabilize ulna

132
Q

What is the primary mover of pronation

A

Pronator quadratus

133
Q

What is the secondary mover of pronation

A

Pronator teres

134
Q

When is the pronator quadratus active

A

With or without resistance at fast and slow speeds

135
Q

Is the pronator quadratus affected by the position of the elbow

A

No

136
Q

When is the pronator teres actively insufficient

A

Flexion of elbow and forearm pronation

137
Q

What does radial hed and capitulum compression create

A

Stability

138
Q

What causes lateral epicondylitis (2)

A
  1. Repetitive use

2. Tensile stressing leading to microtears

139
Q

What causes medial epicondylitis

A

Repetitive use

140
Q

What muscle use causes lateral epicondylitis (1)

A
  1. Extensor carpi radialis brevis
141
Q

What muscle use causes medial epicondylitis (3)

A
  1. Pronator teres
  2. Flexor carpi radialis
  3. Flexor carpi ulnaris
142
Q

What is nursemaid’s elbow

A

Radial head extraction from annular ligament

143
Q

What causes nursemaid’s elbow

A

Longitudinal traction (tensile) force

144
Q

What does the cocking phase of throwing cause

A

Increased tensile stress throwing a ball

145
Q

What type of stress does the cocking phase cause at the elbow

A

Valgus stress

146
Q

Medial epicondylitis may lead to what

A

Increased carrying angle

147
Q

Why does the carrying angle increase with medial epiconylitis

A

Adaptive lengthening of the UCL

148
Q

Medial epicondylitis causes what to happen to the radial head and capitulum

A

Increased compression

149
Q

What happens because of prolonged medial epicondylitis

A

Vascular compromise to articular cartilage and bone

150
Q

What does vascular compromise result in

A

Avascular necrosis

151
Q

Where does the radius and ulna fracture

A

Radius: Distal
Ulna: Proximal olecranon

152
Q

What are the 2 types of radial fractures

A
  1. Colle’s

2. Smith’s

153
Q

Which way is a Colle’s fracture

A

Posterior

154
Q

Which way is Smith’s fracture

A

Anterior