(EXAM 1) Biomechanics of Elbow/Forearm
"Force-couple" used for what motion in the forearm from weight-bearing position?
"Force-couple" used to pronate forearm from weight-bearing position
What structures are taut during pronation at proximal radio-ulnar joint?
1. Annular Ligament 2. Biceps
What structures are lax during passive flexion at the Humeroradial joint?
1. Anterior Articular Capsule
What structures are taut during passive extension at the Humeroradial joint?
1. Anterior Articular Capsule 2. Dermis
Name the 4 primary elbow flexors
1. Biceps Brachii 2. Brachialis 3. Brachioradialis 4. Pronator Teres
What structures are taut during extension of Humero-ulnar joint?
1. Dermis 2. Flexor muscles 3. Anterior Articular capsule
What structures are lax during extension of Humero-ulnar joint?
1. Extensor muscles 2. Posterior articular capsule
What are the secondary pronator muscles?
1. Flexor Carpi Radialis 2. Palmaris Longus Both attaching to the medial epicondyle of humerus 3. Brachioradialis (from supinated position)
What structures are lax during flexion of Humero-ulnar joint?
1. Flexor muscles 2. Anterior Articular Capsule 3. Dermis
External rotation produces pronation at forearm as ulna rotates around fixed radius, what 2 muscles are activated during this activity?
1. Infraspinatus 2. Pronator Quadratus
What is referred to as the "force couple"?
1. Infraspinatus 2. Pronator Quadratus Infraspinatus rotates humerus relative to fixed scapula, whereas pronator quadratus rotates ulna relative to fixed radius
Radius and ulna bound together by what 3 structures?
1. Interosseous membrane 2. Proximal radio-ulnar joint 3. Distal radio-ulnar joint
What structures are lax during passive extension at the Humeroradial joint?
1. Lateral (Ulnar) Collateral Ligament 2. Posterior capsule
What structures are taut during passive flexion at the Humeroradial joint?
1. Lateral (Ulnar) Collateral Ligament 2. Posterior capsule
What are the collateral ligaments?
1. Medial Collateral ligament 2. Lateral Collateral ligament
What muscles, attached to the forearm bones, are activated during pronation?
1. Pronator Teres 2. Flexor Carpi Radialis 3. Pronator Quadratus
What are the primary pronator muscles?
1. Pronator Teres 2. Pronator Quadratus
Name the 2 primary elbow extensors
1. Triceps Brachii 2. Anconeus
What structures are taut during flexion of the Humero-ulnar joint?
1. Ulnar nerve 2. Medial Collateral Ligament - Posterior fibers 3. Posterior Articular Capsule 4. Extensor Muscles
What motions increase tension in Anterior Fibers of Medial Collateral Ligament?
1. Valgus 2. Extension and flexion
What motions increase tension in Posterior Fibers of Medial Collateral Ligament
1. Valgus 2. Flexion
What motions increase tension in the Radial collateral ligament?
1. Varus 2. External rotation
What motions increase tension in the Lateral (ulnar) collateral ligament?
1. Varus 2. External rotation and flexion
What are the primary supinator muscles?
1. biceps 2. supinator
Stability provided by the Anconeus muscles during what activities?
1. extension activities 2. active pronation and supination
The elbow and forearm complex is made up of what four joints?
1. humero-ulnar joint 2. humero-radial joint 3. proximal radioulnar joint 4. distal radioulnar joint
The elbow and forearm complex consists of what 3 bones?
1. humerus 2. radius 3. ulna
In addition to MCL, what groups of muscles also resist excessive valgus- producing strain?
1. proximal fibers of wrist flexor 2. pronator groups of muscles 3. most notably, flexor carpi ulnaris
What are the secondary supinator muscles?
1.Radial Wrist Flexors: 2. Extensor pollicis longus 3. Extensor indicis 4. Brachioradialis (from pronated position) attaching to the lateral epicondyle of the humerus
What is the degrees of maximum range in flexion of the arm?
145*
Hyaline cartilage covers how many degrees of the trochlear notch?
180*
What is the functional arc for supination and pronation?
50* supination through 50* pronation
On average, the forearm rotates through about how many degrees of pronation?
75*
On average, the forearm rotates through about how many degrees of supination?
85*
Although Anconeus is not capable of producing large elbow extension torque, its still provides what?
Although anconeus not capable of producing large elbow extension torque, it still provides important longitudinal and ML stability across humero-ulnar joint
Describe where the Anconeus muscle is. Origin? Insertion?
Anconeus is small triangular muscle spanning posterior side of elbow Muscle located b/w lateral epicondyle of humerus and strip along posterior aspect of proximal ulna
During weight-bearing pronation and supination, _____________ ligament and _________ notch of ulna rotate (spin) around fixed radial head at the proximal radio-ulnar joint.
Annular ligament and radial notch of ulna rotate around fixed radial head.
In the MCL, which fibers are the strongest and the stiffest?
Anterior fibers are strongest and stiffest fibers of medial collateral ligament
Arthrokinematics at humeroradial joint involve _________ of fovea of radial head against rounded _________ of humerus
Arthrokinematics at humeroradial joint involve spin of fovea of radial head against rounded capitulum of humerus
What structure encloses elbow encloses humero-ulnar joint, humeroradial joint, and proximal radio-ulnar joint?
Articular capsule of elbow encloses humero-ulnar joint, humeroradial joint, and proximal radio-ulnar joint
The articular capsule of the elbow is strengthened by what structures?
Articular capsule of elbow strengthened by collateral ligaments.......provide an important source of stability to elbow joint
Articular capsule surrounding the elbow joints as _______ and reinforced by what?
Articular capsule surrounding these joints is thin and reinforced anteriorly by oblique bands of fibrous tissue
As point of comparison, pronator teres has similar flexor moment arm as brachialis, but only about ___% of its physiologic cross-sectional area
As point of comparison, pronator teres has similar flexor moment arm as brachialis, but only about 50% of its physiologic cross-sectional area -Big moment arm, but not as much bulk
In the MCL, which fibers provide the most significant resistance against valgus (abduction) of the elbow?
As such, these fibers provide most significant resistance against valgus (abduction) force to elbow
During fixed pronation and supination, what is happneing at the distal radio-ulnar joint? (be specific)
At distal radio-ulnar joint head of ulna rotates around fixed ulnar notch of radius
Explains what happens when you attempt to catch yourself from a fall
Attempts at catching oneself from a fall may create a severe valgus-producing force to elbow, causing rupture of medial collateral ligament and potentially damaging compression force within humeroradial joint
Based on Brachialis' large cross section across the elbow, its expected to generate the greatest what?
Based on its large physiologic cross-section, brachialis expected to generate greatest force of any muscle crossing elbow
Explain why the Anterior Fibers of the MCL are always taut throughout all movements in the sagittal plane
Because anterior fibers span both sides of axis of rotation, at least some fibers are taut throughout sagittal plane movement -Anterior fibers therefore provide articular stability throughout entire ROM
Because of tight structural fit of _____________ joint, rotation of humerus transferred, nearly degree for degree, to rotating ulna
Because of tight structural fit of humero-ulnar joint, rotation of humerus transferred, nearly degree for degree, to rotating ulna
Why doesn't the transverse fibers of the MCL provide significant articular stability?
Because these fibers originate and insert on same bone, they do not provide significant articular stability
Biceps exhibits relatively low levels of _________ activity when ________ is performed with forearm deliberately held in pronation
Biceps exhibits relatively low levels of EMG activity when flexion is performed with forearm deliberately held in pronation -This lack of muscle activation can be verified by self-palpation
What inactive muscle is being stretched at the proximal radio-ulnar joint during pronation?
Biceps on bicipital tuberosity
Both Infraspinatus and Pronator Quadratus at at either end of the upper extremity produces forces that contribute to what specific force at the forearm?
Both muscles, acting at either end of upper extremity, produce forces that contribute to pronation torque at forearm
What muscle has the largest cross section crossing the elbow?
Brachialis
Why is Brachialis the most powerful elbow flexor?
Brachialis = most powerful elbow flexor (greatest volume and cross-sectional area)
Brachialis sits deep to what muscle?
Brachialis sits deep to biceps
Which muscle is the longest of all of the elbow muscles?
Brachioradialis
Contraction of what muscle forearm to neutral, thumb-up position?
Brachioradialis -From fully pronated position, therefore, muscle supinates; from a fully supinated position, muscle pronates -Contraction of brachioradialis biases forearm toward position that maximizes its moment arm as elbow flexor
Brachioradialis has the longest what that makes it relatively powerful?
Brachioradialis = longest moment arm which makes it relatively powerful (in a pronated position, the bicep is turned off, and the primary flexor is the brachioradialis)
Where is the Brachioradialis palpated?
Brachioradialis muscle can be readily palpated on anterior-lateral aspect of forearm -Resisted elbow flexion, from a position of about 90° of flexion and neutral forearm rotation, causes muscle to stand out or "bowstring" sharply across elbow -Bowstringing of this muscle ↑ its flexion moment arm to length that exceeds that of other flexors
By attaching to ulna, lateral (ulnar) collateral ligament and anterior fibers of medial collateral ligament function as collateral "guy wires" to elbow.......providing what?
By attaching to ulna, lateral (ulnar) collateral ligament and anterior fibers of medial collateral ligament function as collateral "guy wires" to elbow.......providing medial-lateral stability to ulna during sagittal plane motion
What bones articulate to form the humero-ulnar joint?
Capitulum of humerus articulates with radial fovea of radius
During fixed pronation and supination, what is spinning relative to the fovea of the fixed radius at the proximal radio-ulnar joint?
Capitulum of humerus spinning relative to fovea of fixed radius
Combining shoulder and forearm rotations allows hand to rotate nearly ________° in space, rather than only 170° to 180° by pronation and supination alone
Combining these shoulder and forearm rotations allows hand to rotate nearly 360° in space, rather than only 170° to 180° by pronation and supination alone
Compared to the triceps brachii, the anconeus has a relatively small cross-sectional area, and therefore has a small......
Compared with triceps muscle, anconeus has relatively small cross-sectional area and small moment arm for extension
Explain the roll and slide relationship (arthrokinematics) of the Humeroradial joint during flexion of the arm
Concave fovea of radius rolls and slides across convexity of capitulum in the same direction
Explain the roll and slide relationship (arthrokinematics) of the Humeroradial joint during extension of the arm
Concave fovea of radius rolls and slides across convexity of capitulum in the same direction (same as flexion at the humeroradial joint, just in the opposite direction)
During non-weight bearing pronation and supination, _________ of ulnar notch of ________ rolls and slides in similar directions on convex ulna __________ at distal radio-ulnar joint.
Concavity of ulnar notch of radius rolls and slides in similar directions on convex ulna head.
Consider a person bearing weight through an upper extremity with elbow and wrist extended: 1. The person's glenohumeral joint is held in what position? 2. how is the radius and the ulna positioned in full supination?
Consider a person bearing weight through an upper extremity with elbow and wrist extended: 1. Person's glenohumeral joint held partially internally rotated 2.Ulna and radius positioned parallel in full supination ("rod" placed through epicondyles of humerus helps with orientation of this position)
During weight-bearing pronation and supination, Convex ________ head rolls and slides in opposite directions on concave ________ ______ of radius at distal radio-ulnar joint.
Convex ulnar head rolls and slides in opposite directions on concave ulnar notch of radius.
Cubitus Varus deformity is indicated by how many degrees deviated medially?
Cubitus varus deformity depicted with forearm deviated medially 5°.
What motions increase tension in the Annular ligament?
Distraction of radius, external rotation
Regardless of gender, Valgus angle is greater in which arm?
Dominant arm
What structures are lax during unfixed supination at the distal radio-ulnar joint?
Dorsal Capsular Ligament
What structures are taut during unfixed pronation at the distal radio-ulnar joint?
Dorsal Capsular Ligament
During active flexion, radial ___________ is pulled firmly against capitulum by ____________ ______________.
During active flexion, radial fovea is pulled firmly against capitulum by contracting muscles
Explain the roll and slide relationship during extension at the Humero-ulnar joint
During extension at humero-ulnar joint, concave surface of trochlear notch rolls and slides on convex trochlea in the same direction. (same as flexion, just opposite direction)
Explain the roll and slide relationship during flexion at the Humero-ulnar joint
During flexion at humero-ulnar joint, concave surface of trochlear notch rolls and slides on convex trochlea in the same direction.
Why is the Humeroradial joint considered a "shared" joint between the elbow and forearm
During pronation and supination, proximal end of radius rotates at both proximal radio-ulnar and humeroradial joints
During pronation fovea of radial head _________ against capitulum
During pronation fovea of radial head spins against capitulum Spinning occurs around axis nearly coincident with AOR through proximal and distal radio-ulnar joints
EMG studies suggest that brachioradialis is a primary elbow _______, especially during _______ movements against _________ resistance
EMG studies suggest that brachioradialis is a primary elbow flexor, especially during rapid movements against high resistance
The 4 primary elbow flexors produce forces that pass __________ to the medial-lateral AoR at the elbow.
Each of these muscles produces force that passes anterior to medial-lateral AOR at elbow
Interaction b/w elbow and forearm joints greatly ↑ range of what?
Effective hand placement
Elbow extension occurs in what 3 activities?
Elbow extension occurs with activities such as throwing, pushing, and reaching
Elbows axis of rotation extends what direction?
Elbow's axis of rotation (green line) extends slightly obliquely in a medial-lateral direction through capitulum and trochlea
Excessive Cupitus Valgus angle is indicated by how many degrees deviated laterally?
Excessive cubitus valgus deformity shown with forearm deviated laterally 30°. -Extended elbow may show an excessive cubitus valgus that exceeds ~20-25 °
Excessive Cubitus Valgus may overstretch and damage which nerve?
Excessive cubitus valgus may overstretch and damage ulnar nerve as it crosses medial to elbow
What bony outgrowth around the elbow can limit full extension?
Excessive ectopic (bone spur) bone formation around olecranon fossa can therefore limit full extension
In unfixed supination, what is happening at the GH joint?
External rotation at the GH joint note: in unfixed supination, the arm can involve the GH joint, but doesnt have to
In fixed pronation, what is happening at the GH joint?
External rotation of the GH joint
True or False: Posterior Fibers of MCL do not resist valgus force?
FALSE All of the MCL fibers resist valgus force to some extent
True of False: the entire elbow joint is lined with cartilage
FALSE There is a small area on trochlear notch lacking articular cartilage (most of the joint is lined with cartilage)
True of False: on average, men have a greater valgus angle than women by 2*
FALSE Women actually have a greater valgus angle than men by 2*
The Lateral Collateral Ligament becomes taut during what actions?
Fibers become taut during full flexion - check varus
Does fixed pronation and supination occur in a weight-bearing or non-weight-bearing position?
Fixed pronation and supination occurs in a weight-bearing position -Humerus and ulna rotate relative to stationary radius and hand
With radius and hand held firmly fixed with ground, pronation of forearm occurs by external rotation of what 2 structures?
Fixed pronation of forearm occurs by external rotation of humerus and ulna
Explain the roll and slide relationship at the distal radio-ulnar joint during fixed pronation or supination
Fixed pronation/supination at the distal radio-ulnar joint: concave ulna rotates around fixed convex radius
Muscles acting primarily on the wrist, also cross the elbow joint, for this reason, many of the wrist muscles also have the potential to do what?
For this reason, many of wrist muscles have potential to flex or extend elbow This potential relatively minimal and not discussed further
Is supination and pronation a wrist movement or forearm movement?
Forearm movement
Forearm pronation used to place palmar surface of hand down on an object, such as...............
Forearm pronation used to place palmar surface of hand down on an object, such as grasping a coin or pushing up from a chair
Forearm supination occurs during many activities that involve .......
Forearm supination occurs during many activities that involve rotating palmar surface of hand toward face, such as feeding, washing, and shaving
Forearm supination places _________ __________, or supine, and pronation places _________ ___________, or prone
Forearm supination places palm up, or supine, and pronation places palm down, or prone
What is another term for Cubitus Varus deformity?
Gunstock Deformity (because your arm looks like a gun)
Humeroradial joint mechanically linked to kinematics of both _________ and _____________.
Humeroradial joint mechanically linked to kinematics of both elbow and forearm
What structures form the proximal segment of the forearm complex?
Humerus and ulna form proximal segment of forearm complex
Fixed pronation and supination kinematics are essentially an expression of active external and internal rotation of the _______ joint, respectively
Important to note that these pronation and supination kinematics are essentially an expression of active external and internal rotation of GH joint, respectively
What are the dynamic medial stabilizers and why are they called that?
In addition to MCL, proximal fibers of wrist flexor and pronator group of muscles also resist excessive valgus-producing strain at elbow, most notably by flexor carpi ulnaris For this reason, these muscles are referred to as dynamic medial stabilizers of elbow
What position is the radius and ulna parallel?
In full supination radius and ulna parallel
In severe elbow injuries _____________ ___________ of ulna may dislocate posterior to ______________ of humerus.
In severe elbow injuries trochlear notch of ulna may dislocate posterior to trochlea of humerus
In unfixed pronation, what is happening at the GH joint?
Internal rotation at the GH joint note: in unfixed pronation, the arm can involve the GH joint, but it doesnt have to
In fixed supination, what is happening at the GH joint?
Internal rotation of the GH joint
What 2 ligaments make up the Lateral Collateral Ligament?
LCL 1. Radial Collateral Ligament 2. Lateral (Ulnar) Collateral Ligament
What two structures are the primary stabilizers against varus-producing force?
LCL complex and posterior-lateral aspect of capsule are primary stabilizers against varus-producing force
Which ligament is the primary varus stabilizer?
Lateral (Ulnar) Collateral Ligament
Is Lateral Collateral Ligament or Medial Collateral Ligament more variable in form?
Lateral collateral ligament complex of elbow more variable in form than medial collateral ligament
Lateral Collateral Ligament originates from where? And inserts where?
Ligamentous complex originates on lateral epicondyle and immediately splits into two fiber bundles One fiber bundle, known as radial collateral ligament, fans out to blend with annular ligament Second fiber bundle, called lateral (ulnar) collateral ligament, attaches distally to supinator crest of ulna
The radius accepts what percentage of compression force applied through the wrist? What could this cause?
Ligamentous injury may be associated with fracture within humeroradial joint or anywhere along the length of radius— forearm bone that accepts 80% of compression force applied through wrist
Marked stiffness in elbow flexors muscles often cause what in elbow flexion?
Loss of complete extension b/c elbow flexion contracture often caused by marked stiffness in elbow flexor muscles
Medial Collateral ligament is made of what 3 parts?
MCL 1. Anterior Fibers - provides most stability 2. Posterior Fibers - provides little stability 3. Transverse FIbers - provides no stability because origin/insertion on same bone
MCL also susceptible to injury from what types of activities and why?
MCL also susceptible to injury from repetitive, valgus-producing forces to elbow in non-weight-bearing activities, such as pitching baseball and hitting ("spiking") volleyball
When is MCL susceptible to injury?
MCL susceptible to injury when fully extended elbow is violently forced into excessive valgus, often from fall onto an outstretched arm and hand (FOOSH)
Where is the medial-lateral axis of rotation for the Humeroradial joint?
ML axis of rotation in center of capitulum
In children, varus or valgus deformity may result from trauma, such as what?
Marked varus or valgus deformity may result from trauma, such as severe fracture through "growth plate" of distal humerus in children
Maximal range of passive motion generally available to elbow extension is how many degrees?
Maximal range of passive motion generally available to elbow is from 5° beyond neutral (0°)
Maximal range of passive motion generally available to elbow flexion is how many degrees?
Maximal range of passive motion generally available to elbow through 145° of flexion
Maximal shortening of brachioradialis causes full elbow ___________ and ____________ of forearm to near neutral position.
Maximal shortening of brachioradialis causes full elbow flexion and rotation of forearm to near neutral position
Which ligament is the primary valgus stabilizer?
Medial collateral ligament (anterior fibers)
Elbow flexion and extension occurs around a relatively stationary _______________ axis of rotation
Medial-Lateral axis of rotation -passing through vicinity of lateral epicondyle
Moving back to fixed fully supinated position involves _________ __________ of humerus and ulna relative to fixed radius and hand.
Moving back to fully supinated position involves internal rotation of humerus and ulna relative to fixed radius and hand
Radius crosses over the ulna during what motion?
Moving into full unfixed pronation, radius crosses over ulna -AOR (dashed line) extends obliquely across forearm from radial head to ulnar head
Muscles become abnormally stiff after long periods in what position?
Muscles become abnormally stiff after long periods of immobilization in flexed and shortened position Long-term flexion may be result of casting fractured bone or of post-traumatic heterotopic ossification, osteophyte formation, elbow joint inflammation and effusion, muscle spasticity, paralysis of triceps muscle, or scarring of skin over anterior elbow In addition to tightness in flexor muscles, ↑ stiffness may occur in anterior capsule and some anterior fibers of medial collateral ligament
Muscles that attach distally to the radius may do what at the elbow? But remember, these muscles also have potential to pronate or supinate the arm.
Muscles that attach distally on radius may, in theory, flex or extend elbow, but also have potential to pronate or supinate forearm
Muscles that attach distally at the ulna do what at the elbow? But remember, they possess no ability to pronate or supinate arm.
Muscles that attach distally on ulna flex or extend elbow but possess no ability to pronate or supinate forearm
The "screw home" mechanism of the elbow is referring to what?
Natural proximal migration of radius and associated ↑ joint compression of humeroradial joint during active pronation
Explain what the "thumb up" position is.
Neutral or zero reference position of forearm rotation is "thumb-up" position, midway b/w complete pronation and supination
What is the "carrying angle"?
Normal Valgus Angle aka carrying angle -Term "carrying angle" often used, reflecting fact that valgus angle tends to keep carried objects away from side of thigh during walking
Normal Cubitus Valgus angle is indicated how many degrees?
Normal cubitus valgus of elbow shown with an angle of about 15° from longitudinal axis of humerus An average cubitus valgus angle in healthy persons ~13° with standard deviation ~6°
Normally, once in extension, healthy humero-ulnar joint stabilized primarily by ______________ ______________ and ↑ tension in stretched _______________ _______________.
Normally, once in extension, healthy humero-ulnar joint stabilized primarily by articular congruency and ↑ tension in stretched connective tissues
Often after a single traumatic sporting event, rupture of LCL and Posterior-Lateral Capsule can cause what?
Often after a single traumatic sporting event, rupture of this ligament system can cause not only ↑ varus ("adduction") of elbow, but also posterior-lateral rotary instability This instability expressed as excessive external rotation of forearm with subsequent subluxation of both humero-ulnar and humeroradial joints
Brachialis originates where and inserts where?
Origin: anterior humerus Insertion: extreme proximal ulna
In the MCL, the Anterior Fibers originate and insert where?
Origin: anterior part of medial epicondyle Insert: medial part of coronoid process of ulna
Brachioradialis originates where and inserts where?
Origin: lateral supracondylar ridge of humerus Inserts: styloid process of radius
Triceps Brachii originate where?
Origin: medial and lateral head on either side of radial groove on humerus -Medial head has extensive proximal attachment on posterior side of humerus, occupying location relatively similar to that of brachialis on bone's anterior side -Some of more distal fibers of medial head attach directly into posterior capsule of elbow
Biceps Brachii originates where and inserts where?
Origin: on scapula Insertion: radial tuberosity on radius Secondary distal attachments include deep fascia of forearm through an aponeurotic sheet known as fibrous lacertus
In the MCL, the Posterior Fibers originate and insert where?
Origin: posterior part of medial epicondyle Insertion: medial margin of olecranon process
Pain or limited motion at what joint can significantly disrupt functional mobility of entire distal upper extremity?
Pain or limited motion at humeroradial joint can significantly disrupt functional mobility of entire distal upper extremity
What structures are lax during unfixed pronation at the distal radio-ulnar joint?
Palmar Capsular Ligament
What structures are taut during unfixed supination at the distal radio-ulnar joint?
Palmar Capsular Ligament
Persons who lack the last _________ degrees of complete forearm rotation still capable of performing many routine ADLs
Persons who lack last 30° of complete forearm rotation still capable of performing many routine ADLs
Posterior fibers of MCL less defined than anterior fibers and are essentially and are essentially what?
Posterior fibers of MCL less defined than anterior fibers and are essentially thickenings of posterior-medial capsule
Why is the elbow joint considered a modified hinge joint?
Predominant motions are flexion and extension, but the ulna also experiences a slight amount of axial rotation (i.e., rotation around its own longitudinal axis) and side-to-side motion as it flexes and extends
Pronation and supination of forearm functionally associated with internal and external rotation at the ____________.
Pronation and supination of forearm functionally associated with internal and external rotation at the shoulder -Supinate/pronate independent of shoulder -Supinate/pronate with the shoulder - more mobility and greater function
_____________ and ______________ provide mechanism that allows independent "rotation" of hand without obligatory rotation of ulna or humerus
Pronation and supination provide mechanism that allows independent "rotation" of hand without obligatory rotation of ulna or humerus
Pronation and supination require simultaneous movements at what 2 joints? What other joint is required for movement?
Pronation and supination require simultaneous movements at both proximal and distal radio-ulnar joints Pronation and supination also require movement at adjacent humeroradial joint
What muscle is inactive, but stretched during unfixed supination?
Pronator Teres
What structures are taut during unfixed supination at the proximal radio-ulnar join?
Pronator Teres
Which muscle pronates forearm and pulls radius proximally against capitulum
Pronator teres muscle pronates forearm and pulls radius proximally against capitulum
Which joints allows the forearm to rotate into supination and pronation?
Proximal radio-ulnar joint and Distal radio-ulnar joint situated at either end of forearm, allows forearm to rotate into pronation and supination
During non-weight bearing pronation and supination, radial ______ rotates (spins) within ring formed by ______ ligament and radial notch of ulna at the proximal radio-ulnar joint
Radial head rotates (spins) within ring formed by annular ligament and radial notch of ulna.
What structures are considered the distal segment of the forearm complex?
Radius and carpal bones form distal segment of forearm complex
Restriction at what 3 joints would restrict overall movement of forearm rotation?
Restriction at any one of these joints would restrict overall movement of forearm rotation
Several ADLs require only about __________degrees of forearm rotation—from about __________degrees of pronation through __________ degrees of supination
Several ADLs require only about 100° of forearm rotation—from about 50° of pronation through 50° of supination
What is the functional arc of motion within the arm?
Several common activities of daily living use more limited "functional arc" of motion, usually b/w 30° and 130° of flexion
Severe valgus-producing force may also injure what nerve and what group of muscles?
Severe valgus-producing force may also injure ulnar nerve or proximal attachments of pronator-wrist flexor muscles Anterior capsule may also be injured if joint excessively hyperextended
Shoulder ___________ rotation often occurs with pronation, whereas shoulder ____________ rotation often occurs with supination
Shoulder internal rotation often occurs with pronation, whereas shoulder external rotation often occurs with supination
Stretching of ulnar nerve from prolonged or repetitive elbow flexion activities can lead to ________________.
Stretching of ulnar nerve from prolonged or repetitive elbow flexion activities can lead to neuropathy
What liquid area surrounds the inside of the Articular capsule?
Synovial membrane lines the internal surface of the Articular capsule
Synovial membrane lines what part of the Humero-ulnar joint?
Synovial membrane lining internal side of the antererior capsule (extends all the way around both the humero-ulnar joint and Humeroradial joint - everything around the elbow joint)
Explain the roll and spin relationship at the proximal radio-ulnar joint during supination and pronation
TRICK QUESTION Supination and pronation at proximal radio-ulnar joint occurs as rotation of radial head with fibro-osseous ring formed by annular ligament and radial notch of ulna Tight constraint of radial head by fibro-osseous ring prohibits standard roll-and-slide arthrokinematics
True or False: the thumb stays with the radius during pronation
TRUE
True or False: Unlike in lower extremity joints, such as knee, loss of extremes of motion at elbow usually results in only minimal functional impairment
TRUE Unlike in lower extremity joints, such as knee, loss of extremes of motion at elbow usually results in only minimal functional impairment
When are Posterior Fibers of MCL taut?
Taut during extremes of elbow flexion
Forearm rotation (pronation and supination) occurs around what axis?
This forearm rotation occurs around an axis of rotation that extends from radial head through ulnar head—an axis that intersects and connects both radio-ulnar joints
The elbow joint's ability to perform flexion and extension helps with what important functional activities?
This mechanism used for many important activities, such as feeding, reaching, throwing, and personal hygiene
The proximal and distal radioulnar joints allow for what kind of movements without requiring motion from the shoulder?
This pair of articulations allows palm of hand to be turned up (supinated) or down (pronated), without requiring motion of shoulder
Which extensor muscle has the biggest volume, and therefore the most powerful?
Triceps (long head) = big volume = most powerful
What bones articulate to form the humeroradial joint?
Trochlea of humerus articulates with trochlear notch if ulna
Explain the roll and slide relationship at the distal radio-ulnar joint during unfixed pronation or supination
Unfixed pronation/supination at the distal radio ulnar joint: concave radius and carpal bones rotate around fixed convex ulna and humerus concave-on-convex = roll and slide will move in the same direction during pronation and supination
Explain what muscles are being used when screwing in a screw and what they are doing
Vigorous contraction of right biceps, supinator, and extensor pollicis longus muscles to tighten screw using clockwise rotation with screwdriver......triceps muscle activated isometrically to neutralize strong elbow flexion tendency of biceps
Hyaline cartilage covers about how many degrees of the articular surface on trochlea?
about 300*
To some extent, decreased (lack of) pronation and suppination can be compensated for by what?
compensated for by humeral internally and externally rotating shoulder, respectively
Where does the distal radioulnar joint articulate?
distal ends of the ulna and radius
For humero-ulnar joint to be fully extended, what structures require extensibility?
extensibility required in: 1. dermis anterior to elbow 2. flexor muscles 3. anterior capsule 4. anterior fibers of medial collateral ligament
What is the Brachialis' sole function?
flex the elbow
Dislocation of the trochlear notch of the ulna posterior to the trochlea of the humerus is frequently caused from a fall onto an outstretched arm and hand and therefore may also be associated with what?
fracture of radius
In regards to the Humero-ulnar joint, Natural congruency and shape of joint limits motion within what plane?
limits motion primarily within sagittal plane
The transverse fibers of the MCL originate and insert where?
origin: olecranon process of ulna Insert: coronoid process of ulna
During fixed pronation, the proximal radio-ulnar joint, _________ ________, and _________ __________ of ulna rotate around fixed radial head
proximal radio-ulnar joint, annular ligament and radial notch of ulna rotate around fixed radial head
Where does the proximal radioulnar joint articulate?
radial tuberosity of radius into radial notch of ulna
Full extension also requires that prominent tip of olecranon process become wedged into what structure?
requires that prominent tip of olecranon process become wedged into olecranon fossa
During fixed pronation and supination, what is happening at the proximal radio-ulnar joint?
rotation of radius and ulna fixed pronation at forearm -external rotation fixed supination at forearm - internal rotation
Restrictions in passive ROM at the proximal and distal radio-ulnar joints can occur from what?
tightness in muscle and/or connective tissues
Does unfixed pronation and supination occurs in a weight-bearing or non-weight-bearing position?
unfixed pronation and supination occurs in a non-weight-bearing position
