1What 3 bones comprise the elbow and forearm complex?
Humerus, radius, and ulna
2What 4 joints comprise the elbow and forearm complex?
Humero-ulnar, humeroradial, proximal radioulnar, and distal radioulnar joints
3What is the loose-packed position of the humero-ulnar joint?
70° flexion and 10° supination
4What is the close-packed position of the humero-ulnar joint?
Extension
5What is the normal sagittal plane ROM of the humero-ulnar joint?
\$0^\circ\text{–}150^\circ\$
6What is the expected end-feel for humero-ulnar extension?
Bony
7What is the expected end-feel for humero-ulnar flexion?
Soft tissue approximation
8What is the loose-packed position of the humeroradial joint?
Full extension and supination
9What is the close-packed position of the humeroradial joint?
90° flexion and 5° supination
10What is the expected end-feel for pronation and supination at the humeroradial joint?
Soft tissue; capsular
11What is the loose-packed position of the proximal radioulnar joint?
70° flexion and 35° supination
12What is the close-packed position of the proximal radioulnar joint?
5° supination
13What is the normal transverse plane ROM of the radioulnar joints?
\$80^\circ\text{–}0^\circ\text{–}80^\circ\$
14What is the loose-packed position of the distal radioulnar joint?
10° supination
15What is the close-packed position of the distal radioulnar joint?
5° supination
16Why does the axis of rotation for elbow flexion/extension angle slightly superior from medial to lateral?
Due to the long medial lip of the trochlea
17What is normal cubitus valgus commonly called?
The "carrying angle"
18What is the average normal cubitus valgus carrying angle in adults?
\$\sim 13^\circ\$ (with a standard deviation of \$6^\circ\$)
19How does the normal carrying angle compare between women and men?
Women are greater than men by \$\sim 2^\circ\$
20What angle defines excessive cubitus valgus?
\$> 20^\circ\text{–}25^\circ\$
21What nerve may be overstretched in excessive cubitus valgus?
Ulnar nerve
22What angle defines cubitus varus?
\$\sim -5^\circ\$
23What clinical deformity name is given to cubitus varus?
"Gunstock deformity"
24What 3 fiber bundles comprise the medial collateral ligament (MCL) of the elbow?
Anterior, posterior, and transverse bundles
25Which bundle of the MCL is the strongest and stiffest?
Anterior bundle
26What primary mechanical stress does the elbow MCL resist?
Valgus stress
27Which phases of overhead throwing generate the greatest valgus torques at the elbow?
Late cocking and acceleration phases
28What 2 primary bundles form the lateral collateral ligament (LCL) complex of the elbow?
Radial collateral ligament and lateral ulnar collateral ligament (LUCL)
29Where does the lateral ulnar collateral ligament (LUCL) insert?
Supinator crest of the ulna
30What primary mechanical stress does the LCL complex resist?
Varus stress
31What excessive motion does the lateral ulnar collateral ligament (LUCL) specifically prevent?
Excessive supination
32What is the position of comfort for the elbow LCL complex?
\$\sim 70^\circ\text{–}80^\circ\$ flexion
33Spinal cord injuries above which nerve root level eliminate the ability to flex the elbow?
C5 nerve root
34What is the normal passive ROM of elbow flexion/extension?
\$5^\circ\$ beyond neutral (\$0^\circ\$) extension through \$140^\circ\text{–}150^\circ\$ flexion
35What range of flexion represents the 100° functional arc for most elbow ADLs?
\$30^\circ\text{–}130^\circ\$ of flexion
36What bony structures limit full elbow extension at the humero-ulnar joint?
Olecranon process fitting into the olecranon fossa
37Which fibers of the MCL elongate and become taut during full elbow flexion?
Posterior fibers of the MCL
38What bones articulate to form the humeroradial joint?
Fovea of the radial head and capitulum of the humerus
39What percentage of resistance against a valgus stress is provided by the humeroradial joint?
\$\sim 50\%\$
40At what angle and direction are the fibers of the central band of the interosseous membrane oriented?
Distal-medially from the radius about \$20^\circ\$ to the ulna
41How thick is the central band compared to other regions of the interosseous membrane?
2 times as thick
42What tendon has a tensile strength approximately equal to the central band of the interosseous membrane?
Patellar tendon
43What is the proposed function of the oblique cord of the interosseous membrane?
Helps limit distal migration of the radius on the ulna
44What percentage of interosseous membranes contain distal oblique fibers?
Only \$40\%\$
45What muscle lies superficial to the distal oblique fibers of the interosseous membrane?
Pronator quadratus
46What is the primary function of the distal oblique fibers of the interosseous membrane?
Stabilize the distal radioulnar joint
47What percentage of compression force crossing the wrist passes through the radiocarpal joint?
\$\sim 80\%\$
48What percentage of compression force crossing the wrist passes through the medial ulnocarpal space?
Only \$20\%\$
49How does the central band of the interosseous membrane direct compression force across the forearm?
Transmits force proximally from the radius to the ulna
50What compressive force can be generated at the humeroradial joint during maximum voluntary contraction near full extension?
\$3\text{–}4\times\$ body weight
51What happens to the radius if the interosseous membrane tears?
Proximal migration of the radius
52Which structures resist distally applied (distraction) forces on the radius?
Oblique cord, annular ligament, and brachioradialis
53What condition results from a slip of the radial head through the annular ligament?
"Pulled-elbow syndrome" (nursemaid's elbow or babysitter's elbow)
54At which position of the forearm is the central band of the interosseous membrane least taut?
Full pronation
55At which position of the forearm is the central band of the interosseous membrane most taut?
Full supination
56Where is the longitudinal axis of rotation for forearm pronation and supination located?
Passes obliquely from the radial head through the ulnar head
57Which forearm bone is the primary moving bone during pronation and supination?
Radius
58What structures articulate to form the distal radioulnar joint?
Convex ulnar head, concave ulnar notch of the radius, and proximal surface of the triangular fibrocartilage
59Where does the triangular fibrocartilage attach medially?
Ulnar styloid process
60What is the normal passive translation of the distal radioulnar joint with dorsal/palmar forces?
\$\sim 5.5\text{ mm}\$ (\$\sim 1/4\text{ inch}\$)
61What structures comprise the triangular fibrocartilage complex (TFCC)?
Articular disc, dorsal and palmar capsular ligaments, and ulnar collateral ligament
62What is the primary stabilizer of the distal radioulnar joint?
Triangular fibrocartilage complex (TFCC)
63What muscles and fibrous structures provide secondary stability to the distal radioulnar joint?
Pronator quadratus, tendon of ECU, and distal oblique fibers of the interosseous membrane
64What functional arc of forearm pronation and supination is needed for most daily activities?
\$100^\circ\$ functional arc (\$50^\circ\$ pronation and \$50^\circ\$ supination)
65What arthrokinematic motion occurs at the distal radioulnar joint during supination?
Concave ulnar notch of radius rolls and slides in the same direction on the convex ulnar head
66What percentage of the ulnar notch contacts the ulnar head during extreme pronation or supination?
\$\sim 10\%\$
67What percentage of the ulnar notch contacts the ulnar head in the neutral/midposition?
\$60\%\$
68Which capsular ligament tightens to stabilize the distal radioulnar joint during supination?
Palmar capsular ligament
69Which capsular ligament tightens to stabilize the distal radioulnar joint during pronation?
Dorsal capsular ligament
70By what percentage does full pronation slacken the palmar capsular ligament at the distal radioulnar joint?
\$\sim 70\%\$
71What is the most active and consistently used forearm pronator?
Pronator quadratus
72What arthrokinematic motion occurs at the humeroradial joint during pronation and supination?
Spin (only) of the concave radial fovea on the convex capitulum
73Why are compressive force and proximal radial migration greater in pronation than in supination?
Due to a less taut interosseous membrane in pronation
74When the hand and radius are fixed to the ground, what muscles form a force-couple to produce pronation?
Infraspinatus (externally rotating humerus) and pronator quadratus
75Which tendon is irritated in lateral epicondylitis?
Common extensor tendon (especially ECRB)
76Which tendon is irritated in medial epicondylitis?
Common flexor tendon
77What anatomical rule dictates whether an elbow-crossing muscle can pronate or supinate the forearm?
It must attach distally to the radius or hand (not the ulna)
78What are the 3 primary elbow flexor muscles?
Biceps brachii, brachialis, and brachioradialis
79What condition produces maximal EMG activity in the biceps brachii?
Simultaneous elbow flexion and supination
80How much greater are elbow flexion torques in full supination compared to full pronation?
\$\sim 20\%\text{–}25\%\$ stronger
81Which elbow flexor has the largest cross-sectional area (CSA) and generates the greatest force?
Brachialis
82Which muscle is the longest of all elbow flexors and has the greatest internal moment arm?
Brachioradialis
83How do elbow flexor torques compare in magnitude to elbow extensor torques?
Flexor torques are \$\sim 70\%\$ greater than extensor torques
84At what elbow joint angle is the greatest flexor torque produced?
\$\sim 85^\circ\text{–}95^\circ\$ of flexion
85At what elbow joint angle is maximal muscle force generated by the elbow flexors?
\$\sim 80^\circ\$ of flexion
86At what elbow joint angle is the internal moment arm greatest for the elbow flexors?
\$\sim 100^\circ\$ of flexion
87Which muscle acts as a synergist to the biceps brachii during high-power elbow flexion by extending the shoulder?
Posterior deltoid
88What are the 2 primary elbow extensor muscles?
Triceps brachii and anconeus
89Where do all heads of the triceps brachii and the anconeus insert?
Near or onto the olecranon process of the ulna
90Which muscle is typically the first elbow extensor recruited to initiate and maintain low-level extension?
Anconeus
91Which head of the triceps is called the "workhorse of extensors" because it remains active across most extension movements?
Medial head
92In what order are the triceps heads recruited as effort increases from low to maximal?
Medial head \$ightarrow\$ lateral head \$ightarrow\$ long head
93Which muscle flexes the shoulder to counteract the shoulder extension torque of the triceps long head during pushing?
Anterior deltoid
94At what elbow angle is maximal elbow extension torque produced?
\$\sim 80^\circ\text{–}90^\circ\$ of flexion
95At what elbow angle is the internal moment arm of the triceps brachii largest?
Close to full extension
96What are the 2 primary pronator muscles of the forearm?
Pronator teres and pronator quadratus
97What are the 2 heads of the pronator teres?
Humeral head and ulnar head
98What nerve can be entrapped between the 2 heads of the pronator teres?
Median nerve
99What are the 2 primary supinator muscles of the forearm?
Supinator and biceps brachii
100How much greater is the cross-sectional area of the biceps brachii compared to the supinator?
3 times greater
101At what elbow angle does the biceps brachii have its greatest leverage to supinate?
\$\sim 90^\circ\$ of elbow flexion
102How much greater is supinator isometric torque compared to pronator isometric torque?
\$\sim 25\%\$ greater
103Which muscle contracts during strong supination to counteract the elbow and shoulder flexion torques of the biceps?
Triceps brachii
104What are the proximal origins of the biceps brachii?
Long head: supraglenoid tubercle; Short head: coracoid process
105Where does the biceps brachii insert distally?
Radial tuberosity and deep fascia via the bicipital aponeurosis (fibrous lacertus)
106What are the distal insertion sites of the brachialis muscle?
Coronoid process and ulnar tuberosity
107Where does the brachioradialis originate and insert?
Origin: lateral supracondylar ridge of humerus; Insertion: styloid process of radius
108Where does the long head of the triceps brachii originate?
Infraglenoid tubercle of the scapula
109What percentage of total elbow extensor torque is produced by the anconeus?
\$\sim 15\%\$
110Where does the supinator muscle insert?
Proximal 1/3 of the radius
111What nerve roots comprise the musculocutaneous nerve?
\$C_5\text{–}C_7\$
112Which muscles are innervated by the musculocutaneous nerve?
Biceps brachii, brachialis, and coracobrachialis
113What cutaneous region is supplied by the musculocutaneous nerve (as the lateral antebrachial cutaneous nerve)?
Lateral forearm
114What nerve roots comprise the radial nerve?
\$C_5\text{–}T_1\$
115From which cord of the brachial plexus does the radial nerve directly arise?
Posterior cord
116Which elbow and forearm muscles receive motor innervation from the radial nerve?
Triceps, anconeus, brachioradialis, and supinator
117What nerve roots comprise the median nerve?
\$C_6\text{–}T_1\$
118Which forearm muscles receive motor innervation from the median nerve?
Pronator teres, pronator quadratus, and most wrist/finger flexors
119Which sensory area is supplied by the median nerve?
Lateral 2/3 of the palm, palmar surface of the thumb, index, middle, and lateral half of the ring finger
120What nerve roots comprise the ulnar nerve?
\$C_8\text{–}T_1\$
121From which cord of the brachial plexus does the ulnar nerve directly arise?
Medial cord
122Which forearm muscles are innervated by the ulnar nerve?
Flexor carpi ulnaris (FCU) and the medial half of flexor digitorum profundus (FDP)
123What is the sensory distribution of the ulnar nerve?
Medial 1/3 of the hand, little finger, and medial half of the ring finger
124Under what fibrous band above the medial epicondyle can the median nerve become entrapped?
Ligament of Struthers
125What pinch deformity occurs with anterior interosseous nerve entrapment?
Pad-to-pad pinch instead of tip-to-tip pinch
126Through which muscle and fibrous arch can the deep branch/posterior interosseous nerve of the radial nerve become entrapped?
Supinator muscle at the Arcade of Frohse
127Through which fibro-osseous tunnel behind the medial epicondyle does the ulnar nerve pass?
Cubital tunnel