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Make-up of the elbow and forearm complex
3 bones and 4 joints TERM 2
Four articulations within the elbow and
forearm complex
DEFINITION 2 humero-ulnarhumeroradialproximal radio-ulnar jointdistal radio-ulnar joint TERM 3
The elbow consists of which joints
DEFINITION 3 humeroulnarhumeroradial TERM 4
What kind of joint is the elbow?
DEFINITION 4 modified hinge joint because the ulna experiences a slight amount of axial rotation and side-side motion as it flexes and extends TERM 5
Elbow flexion and extension occur around
what axis of rotation
DEFINITION 5 flex/ext occur around the medial/lateral axis of rotation
From medial to lateral, the axis courses
slightly superiorly, WHY?
in part to the distal prolongation of the medial lip of the trochleathe asymmetry causes the ulna to deviate laterally relative to the humerus TERM 7
What is the natural frontal plane angle made
by the extended elbow called?
DEFINITION 7 the normal cubitus valgus (carrying angle) TERM 8
What is the average carrying
angle?
DEFINITION 8 about 13 degrees with SD of 6 degreeswomen have a greater valgus of about 2 degrees largervalgus angle is greatest in dominant arm TERM 9
The articular capsule of the elbow encloses
which joints?
DEFINITION 9 contains humeroulnar, humeroradial and proximal radioulnar jointarticular capsule is thin with a synovial membrane lining the internal surface of the capsule TERM 10
How is the articular capsule of the elbow
strengthened?
DEFINITION 10 by collateral ligaments which provide important source of stability to elbow joint
What other muscles resist excessive valgus-
producing strain at the elbow
proximal fibers of wrist flexors and pronators most notably flexor carpi ulnaris referred to as dynamic medial stabilizers of the elbow TERM 17
The lateral collateral ligament complex
originates where?
DEFINITION 17 on the lateral epicondyle and immediately splits into two fiber bundles TERM 18
2 bundles of the lateral collateral ligament
DEFINITION 18 radial collateral ligament -- fans out to blend with the annular ligament lateral (ulnar) collateral ligament -- attaches distally to the supinator crest of the ulna both fibers are taut in full extension TERM 19
The lateral collateral ligament complex
stabilizes against what type of force?
DEFINITION 19 a varus producing force TERM 20
Annular ligament
DEFINITION 20 thick circular band of CT connecting to ulna on either side of the radial notch the internal circumference is lined with articular cartilage
The external surface of the annular ligament
serves as an attachment for what?
external surface serves as an attachment for the elbow capsule, radial collateral ligament and the supinator muscle TERM 22
What is the maximal range of passive motion
available at the elbow
DEFINITION 22 5 degrees beyond neutral 0 degrees 145 degrees flexion TERM 23
ADL's require about how much elbow flexion?
DEFINITION 23 between 30 degrees and 130 degrees of flexionloss of extremes of motion results in minimal functional impairment TERM 24
Humeroulnar joint is what?
DEFINITION 24 the articulation between the concave trochlear notch of the ulna and the convex trochlea of the humerus TERM 25
What happens at the humero-ulnar joint
during flexion?
DEFINITION 25 concave surface of the trochlear notch rolls and slides on the convex trochlea
Primary function of the interosseous
membrane
bind the radius to the ulna serve as a stable attachment site for extrinsic muscles of the hand provide a mechanism for transmitting force proximally through the upper limb TERM 32
What % of compression force coming through
the wrist is directed through the radiocarpal
joint?
DEFINITION 32 80% of the forceremaining 20% crosses the medial side of the wrist through the soft tissues in the ulnocarpal space TERM 33
The interosseous membrane is not aligned to
resist what kind of forces?
DEFINITION 33 distally applied forces on the radius TERM 34
Distally applied forces do what to the
interosseous membrane?
DEFINITION 34 distal pull on radius slackens rather than tenses the interosseous membrane places more stress on oblique cord and annular ligament contraction of brachioradialis and other muscles involved in grasp can assist with holding the radius and load firmly against the capitulum of the humerus may lead to fatigue in muscles characterized by a deep ache in the forearmshifting the load to shoulder level lets interosseous membrane assist with dispersing the load more evenly through the forearm TERM 35
What are the two joints of the forearm?
DEFINITION 35 proximal radio-ulnar joint distal radio-ulnar joint
In the proximal radio-ulnar joint, what holds
the two bones together?
a fibro-osseous ring holds the radial head against the ulnathis ring is formed by the radial notch of the ulna (25%) and the annular ligament (75%) TERM 37
The distal radio-ulnar joint consists of
what?
DEFINITION 37 the convex head of the ulna resting on the shallow concavity formed by the ulnar notch on the radius and the proximal surface of an articular disc TERM 38
How is the distal radio-ulnar joint
stabilized?
DEFINITION 38 stability is furnished through the activation of muscles plus CT TERM 39
The articular disc at the distal radio-ulnar
joint is also known as what?
DEFINITION 39 triangular fibrocartilagenamed due to its shape and predominant tissue type TERM 40
What is the function of the Triangular
fibrocartilage complex?
DEFINITION 40 the disc holds the head of the ulna into the ulnar notch of the radius during supination and pronation
Pronation and Supination require
simultaneous movements where?
at both the proximal and distal radio-ulnar joints as well as at the adjacent humeroradial joint TERM 47
How does supination at the proximal radio-
ulnar joint occur?
DEFINITION 47 occurs as rotation of the radial head within the fibro-osseous ring formed by the annular ligament and the radial notch of the ulna tight constraint of the radial head by this fibro-osseous ring prohibits standard roll and slide at this joint TERM 48
How does supination at the distal radio-ulnar
joint occur?
DEFINITION 48 as the concave ulnar notch of the radius rolls and slides in similar directions on the head of the ulna the proximal surface of the articular disc remains in contact with the ulnar headat the end of the range of supination the palmar capsular ligament is stretched to its maximal length TERM 49
How does pronation at the proximal and distal
radio-ulnar joints occur?
DEFINITION 49 full pronation elongates and increases tension in the dorsal capsular ligament at the distal radio-ulnar joint slackening the palmar capsular ligament to about 70% of its original length TERM 50
During pronation and supination, the proximal
end of the radius rotates where?
DEFINITION 50 at both the proximal radio-ulnar joint and at the humeroradial joint
Arthrokinematics at the humeroradial joint
during pronation and supination
the fovea of the radial head spins on the rounded capitulum of the humerus pronator teres contracts as well causing humeroradial compression TERM 52
Based on its location, the humeroradial joint
is mechanically linked to what?
DEFINITION 52 the kinematics of both the elbow and forearm TERM 53
Dysfunction at the humeroradial joint can lead
to what?
DEFINITION 53 decreased functional mobility of the entire upper extremity TERM 54
What movements occur when the upper limb
is in a weight bearing position?
DEFINITION 54 the humerus and ulna rotate relative to a fixed radius and hand TERM 55
What movements occur with WB pronation at
the distal radioulnar joint?
DEFINITION 55 pronation of the forearm occurs by and external rotation of the humerus and ulnathe convex head of the ulna rotates and slides in opposite directions around the fixed concave ulnar notch of the radius
Biceps brachii attachment
Proximally at the scapula -- long head and short headdistally at the radial tuberosity as well as the deep fascia of the forearm through fibrous lacertus TERM 62
When does the biceps produce a maximal
EMG?
DEFINITION 62 when flexing and supinating simultaneously TERM 63
Brachialis attachments
DEFINITION 63 deep to biceps proximally on anterior humerusdistally on the extreme proximal ulna -- ulnar tuberosity and coronoid process TERM 64
When does the brachialis produce the
greatest force?
DEFINITION 64 flexion of the elbow generates the greatest force of any muscles crossing the elbowsince it attaches to the ulna it is not effected by forearm positioning TERM 65
Brachioradialis attachments
DEFINITION 65 longest of elbow muscles proximally on the lateral supracondylar ridge of the humerusdistally near the styloid process of the radius
Brachioradialis fxn
flexes the elbow and rotates the forearm to the neutral (thumb's up) position TERM 67
Triceps attachments
DEFINITION 67 proximally: long head -- infraglenoid tuberclelateral head -- superior and lateral to the radial groove of the humerusmedial head -- medial to the radial groove of the humerusdistally: long head -- olecranon process of ulnalateral head -- olecranon process of ulnamedial head -- olecranon process of ulna with some fibers inserting directly on the posterior capsule of the elbow drawing the capsule tight during extension TERM 68
Long head of triceps brachii fxn
DEFINITION 68 extends elbow, adducts the shoulderlargest volume TERM 69
Anconeus attachments
DEFINITION 69 small triangular muscle on posterior elbowproximally on the lateral epicondyle of the humerusdistally to the posterior proximal ulna TERM 70
Fxn of anconeus
DEFINITION 70 small cross sectional areaprovides important longitudinal and medial-lateral stability across the humero-ulnar joint which is important during extension activities
Supinator function
relentless supinatorused for lower power tasks that require only supination vs. higher power tasks associated with flexion where the biceps brachii are recruited TERM 77
Why would using the biceps to perform simple
low power tasks be inefficient?
DEFINITION 77 because you would need additional muscles like the triceps and posterior deltoid to antagonize an undesired movement of the biceps at the shoulder and elbow TERM 78
Law of Parsimony
DEFINITION 78 As force increases: small, one joint muscles are recruited first, larger, two joint muscles are recruited second. Minimizes muscle fibers activated, minimizes neutralizers that must be activated TERM 79
Biceps effectiveness and supination
DEFINITION 79 effectiveness as a supinator is greatest when elbow is flexed to 90 degrees TERM 80
Muscles of pronation
DEFINITION 80 pronator teres pronator quadratus
Pronator teres
has two heads: humeral and ulnarthe median nerves passes through these two heads TERM 82
Pronator teres function
DEFINITION 82 forearm pronator and elbow flexorused during high power pronation activities TERM 83
Pronator quadratus
DEFINITION 83 has two heads: superficial and deep TERM 84
Pronator quadratus functions
DEFINITION 84 the most active and consistently used pronator muscle involved in all pronation movements regardless of the power demands or the amount of associated elbow flexion TERM 85
How is the pronator quadratus an effective
torque producer?
DEFINITION 85 has a line of force oriented almost perpendicular to the forearms axis of rotation
