Elbow and Forearm + review game questions
Triceps function
-3 heads: long, lateral, medial -Origin: infraglenoid tubercle -Insertion: olecranon process -Action: all heads active w/ resisted extension -Max torque at 90º
How does torque generated by elbow flexors vary?
-Age, gender, strength training, speed of contraction, dominant side (higher torque), forearm position (torque w/ forearm supinated are 20-25% greater) -MAX torque for ALL FLEXORS at about 90º flexion
What structures limit pronation at the proximal and distal RU joint?
-Biceps or supinator muscles -Dorsal capsular ligaments (at distal RU) -TFCC
What joint is the stability provided by for the elbow joint?
-Bony stability: provided by HU joint -Ligamentous stability: at all joints
Sensory innervation of proximal RU joint
-C6-C7 roots -Travel in median nerve
Sensory innervation of HU and HR joints
-C6-C8 roots -Fibers from these roots carried primarily by musculocutaneous, radial, ulnar, and median nerves
Sensory innervation of distal RU joint
-C8 roots -Travel in ulnar nerve
Torque generated by elbow extensors
-Elbow extensors provide static stability to elbow -Elbow extensors produce maximal torque when elbow is flexed to 90º
Pronator quadratus function
-Extreme distal end of forearm and deep to all wrist flexors -Most active and consistently used pronator muscle, involved during all pronation movements (both low and high level)
What type of joint is the distal RU joint?
-Gliding joint -Joint firmly connects the distal ends of radius and ulna (laxity can cause problems)
What kind of joint is the distal RU joint?
-Gliding joint (in same direction) -Convex head of ulna articulates with concave ulnar notch of the radius -Has own joint capsule
Brachioradialis function
-Longest of all elbow flexors -Origin: Lateral supracondylar ridge of humerus -Insertion: Near radial styloid process -Action: Elbow flexor especially during movements with high resistance (recruit when we need extra force)
Triangular Fibrocartilage Complex
-Made up of palmar and dorsal RU ligaments from borders -Consists of disc, capsular ligaments, ulnar collateral lig, distal RU legs at distal RU jt -Occupies most of ulnocarpal space and connects distal radius and ulna -Primary stabilizer of distal RU jt
Distal RU joint ligaments: dorsal (posterior) RU ligament
-Mirror image of palmar ligament on posterior/dorsal side -Limits PRONATION
Biceps brachii function
-Multijoint (shoulder and elbow) -Origin: supraglenoid tubercle of scapula (long head), coronoid process (short head) -Insertion: radial tuberosity, bicipital aponeurosis -Action: FLEXION and SUPINATION -Greatest torque production: 85-95º flexion
What is the carrying angle?
-Normal "valgus angle" of the elbow -due to more distal medial lip of trochlea -joint axis is oblique, so the ulna is deviated laterally relative to the humerus -average angle is 13º +/- 6º -carrying angle greater on dominant arm and greater for women than men by 2º -measure w/ prox arm on mid shaft of humerus and distal arm on mid shaft of ulna
Label bony structures on posterior humerus
-Olecranon fossa -Trochlea -Medial epicondyle -Lateral epicondyle
Label bony structures on the ulna
-Olecranon process -Coronoid process -Trochlear notch (fits into trochlear groove on humerus) -Longitudinal crest/ridge (aka trochlear ridge) -Radial notch -Supinator crest -Tuberosity of ulna -Ulnar head -Styloid process
Supinator muscle function
-Origin: lateral epicondyle and supinator crest -Insertion: proximal 1/3 of radius -Action: forearm supinator regardless of position, like brachialis for flex -Significant EMG activity regardless of elbow angle, speed, or power -Recruit for low power takes for supination motion only
What type of joint is the proximal RU joint and what type of motion does it allow?
-Pivot joint -Allows supination and pronation
Biceps brachii function (for supination)
-Primary supinator when elbow is flexed -Normally recruited during high power supination activities when extra force needed -Most effective in 90º flexion -Active w/ resisted and nonresisted flexion
What structures limit supination at the proximal and distal RU joint?
-Pronator teres -Pronator quadratus -Interosseous membrane -Palmar capsular ligaments (only at distal RU) -TFCC -Oblique cord
Label bony structures on the radius
-Radial head -neck -fovea -radial (bicipital) tuberosity -Ulna notch (distal) -Styloid process
Distal RU joint ligaments: palmar (anterior) RU ligament
-Runs from distal ulna near styloid process to distal radius on anterior/palmar side -Limits SUPINATION
What is the function of the interosseous membrane?
-Serves as stable attachment for several extrinsic muscles of hand -provides mechanism for transmitting force proximally through upper limb (after wrist and TFCC, force is transmitted to the ulna and allows HU and HR joints to share compressive forces at elbow - due to central band fiber direction of interosseous membrane)
Pronator teres function (for flexion)
-Similar flexor moment as brachialis -Also active with resisted elbow flexion
Brachialis function
-Single joint - WORKHORSE OF FLEXION -Origin: Anterior humerus -Insertion: Proximal ulna at ulnar tuberosity -Action: Elbow flexion (deep to biceps) -Greatest torque production: 90º flexion
Anconeus function
-Small triangular m. spanning posterior side of elbow -Relatively small CSA and moment arm -Provides longitudinal and med/lat stability across HU jt, guides motion
Pronation of forearm at proximal RU joint motion/arthrokinematics
-Spin -Rotation of radial head within annular ligament -There is a tight fit, so no standard roll and glide IF THERE WAS A GLIDE: there would be anterior roll with posterior glide (different directions because it is the convex radius rotating on concave radial notch)
Supination of forearm at proximal RU joint motion/arthrokinematics
-Spin -Rotation of radial head within annular ligament -There is a tight fit, so no standard roll and glide IF THERE WAS A GLIDE: there would be posterior roll with anterior glide (different directions because it is the convex radius rotating on concave radial notch)
Perarticular connective tissue: articular capsule
-Thin anteriorly and posteriorly, thickened by collateral ligaments at side -synovial membrane
Label these bony structures on mid to distal humerus (anterior)
-Trochlea -medial/lateral lips of trochlea -trochlear groove -coronoid fossa -capitulum -medial epicondyle (sticks out more than lateral epicondyle) -lateral epicondyle -medial and lateral supracondylar ridges
Pronator teres function (for pronation)
-Two heads (humeral and radial) - MEDIAN NERVE IN B/W (if pronator teres is tight = median n. entrapment) -Greatest activity during high powered pronation -Triceps is important here in neutralizing ability of pronator teres to flex the elbow
What is the function of the elbow?
-lengthen or shorten arm -move hand through space -feeding, reaching, throwing, personal hygiene
What 3 CTs make up the proximal RU joint?
1) Annular ligament: thick circular band of CT that connects ulna on either side of radial notch, inner surface is cartilaginous and reduced friction of radial head, outer surface is attachments of joint capsule, supinator, radial LCL 2) Quadrate ligament: thin fibrous lig, arises just below radial notch and attaches to medial neck of radius, keeps head aligned w/ notch, may limit end range of pronation and supination 3) Oblique cord: from lat tuberosity of ulna to area below radial tuberosity, assists in holding radial head in alignment w/ ulna, taut during supination
What are the 3 bundles of the medial collateral ligament?
1) Anterior fibers: most important fibers - strongest and stiffest, runs from medial epicondyle to coronoid process, provides most significant resistance against valgus force through flex and ext 2) Posterior fibers: run from medial epicondyle to olecranon process, less defined than anterior, thickening of posterior/medial capsule, gets more taut in flexion 3) Transverse fibers: run from olecranon to coronoid process, originates and inserts on ulna so no significant joint stability
Elbow flexors (4)
1) Biceps brachii 2) Brachialis 3) Brachioradialis 4) Pronator teres
What are the 4 joints of the elbow?
1) Humeroulnar joint (HU joint) 2) Humeroradial joint (HR joint) 3) Proximal radioulnar joint (prox RU joint) 4) Distal radioulnar joint (distal RU joint)
What are the 2 ligaments of distal RU joint and what motions do they limit?
1) Palmar (anterior) RU ligament (limits SUPINATION) 2) Dorsal (posterior) RU ligament (limits PRONATION) (are the borders of TFCC)
Pronator muscles (2)
1) Pronator teres 2) Pronator quadratus
What are the 2 bundles of the lateral collateral ligaments?
1) Radial collateral ligament: from lateral epicondyle to annular ligament 2) Lateral (ulnar) collateral ligament: from lateral epicondyle to supinator crest on ulna, fibers taut during flexion
Supinator muscles (2)
1) Supinator muscle 2) Biceps brachii
Elbow extensors (2)
1) Triceps 2) Anconeus
Distal RU joint resting position
10º supination
Functional "arc" of ROM at elbow
30º short of zero to 130º
Proximal RU joint resting position
35º supination, 70º elbow flexion
How far does the trochlear project anteriorly to the humeral shaft (HU joint)?
45º anteriorly - allows for minimal side to side motion
Normal ROM of elbow joint
5-0-145º
Distal RU closed pack position
5º supination
Proximal RU joint closed pack position
5º supination
Whats the resting position of proximal RU joint
70 flexion 35 supination
What is the resting position at the HU joint?
70º flexion with 10º supination
What is the CPP of the HR joint?
90º flexion with 5º supination HR: 9-5 closed
Name the 2 ligaments associated with the proximal radioulnar joint.
Annular ligament, quadrate ligament (oblique cord, maybe. More distal)
When the elbow flexes, the radius glides in the blank direction.
Anterior
How to side humerus
Anterior = 2 fossas (radial and coronoid fossa) Posterior = 1 fossa (olecranon fossa)
Name bundle of MCL
Anterior, posterior, transverse
This muscle can carry out elbow flexion effectively regardless of forearm supination or pronation
Brachialis
What elbow flexor has greater compressor component and small rotary component
Brachioradialis
Pronation of forearm at distal RU joint motion/arthrokinematics
Concave radius rolls and glides on ulna in the same direction = anterior roll and glide
Supination of forearm at distal RU joint motion/arthrokinematics
Concave radius rolls and glides on ulna in the same direction = posterior roll and glide
Arthrokinematics of proximal RU joint
Convex head of radius articulates with concave radial notch, only spin occurs
Arthrokinematics of distal RU joint
Convex head of ulna articulates with concave ulnar notch of the radius
Why is the axis of motion at the elbow joint oblique?
Due to medial lip of trochlea extending more distally and the orientation of the trochlear groove
What would 25 degrees of valgus at the HU joint be called?
Excessive cubital valgus
Herniated disk in spine compression on C6 affected muscle and limited movement?
Flexion: Brachialis, bicep, brachioradialis
The elbow is a modified hinge joint: during flexion and extension, how does the ulna move?
Flexion: ulna turns and glides slightly laterally Extension: ulna turns and glides slightly medially
What is the closed pack position of the HU joint?
Full elbow extension with supination
What is the resting position of the HR joint?
Full elbow extension with supination
What is the resting position of the radial humeral joint
Full extension and supination
Arthrokinematics of HR joint during elbow flexion
HR joint: concave radius on convex capitulum of humerus = roll and glide in same direction = ANTERIOR
Arthrokinematics of HR joint during elbow extension
HR joint: concave radius on convex capitulum of humerus = roll and glide in same direction = POSTERIOR
Arthrokinematics of HU joint during elbow flexion
HU joint: concave ulna on convex trochlea = roll and glide in same direction = ANTERIOR Ulna: slight turn and glide laterally (on long axis)
Arthrokinematics of HU joint during elbow extension
HU joint: concave ulna on convex trochlea = roll and glide in same direction = POSTERIOR Ulna: slight turn and glide medially
What is the function of the annular ligament
Holds radial head in the radial notch of the ulna
What are the 3 bones of the elbow?
Humerus, ulna, radius
What covers the 3 joints of the proximal elbow joint?
Joint capsule -reinforced by oblique fibrous bands anteriorly and collateral ligaments medially and laterally
What are the primary stabilizers against varus forces?
LCL complex and posterior/lateral capsule
What cutaneous nerve innervates the lateral forearm? What nerve does it begin as in the lateral cord of the brachial plexus?
Lateral antebrachial cutaneous nerve of the forearm, Starts musculocutaneous
Which ligaments for elbow joint blend with the capsule?
Medial and lateral collateral ligaments - are thickening of the capsule
Carrying angle at the elbow is due to what factor?
Medial lip of the trochlea extends further
What type of joint is the elbow joint and why?
Modified hinge (synovial) joint -due to some axial rotation and side/side motion of ulna
Normal and functional motion for supination and pronation
Normal: Supination: 0-85º Normal: Pronation: 0-75º Functional motion: 50º each direction
Which ligament at distal RU jt limits supination
Palmar
Lig of distal RU joint
Palmar and dorsal
Types of RU joints
Proximal RU = pivot Distal RU = gliding planar
Name the bundles of the LCL
Radial and Ulnar collateral
Supinator is innervated by what nerve, name another muscle innervated by this nerve?
Radial n, triceps
Axillary nerve: roots, cord, motor and sensory inn.
Roots: C5-C6 Cord: Posterior Motor inn: deltoid, teres minor Sensory inn: cutaneous to shoulder
Musculocutaneous nerve: roots, cord, motor and sensory inn.
Roots: C5-C7 Cord: Lateral Motor inn: biceps brachii, brachialis, coracobrachialis Sensory inn: distal cutaneous anterior forearm
Radial nerve: roots, cord, motor and sensory inn.
Roots: C5-T1 Cord: Posterior Motor inn: triceps, brachioradialis, wrist extensors, supinators, ABD pollicis longus and brevis, extensor pollicis longus, extensor indicis Sensory inn: cutaneous to posterior arm and hand
Median nerve: roots, cord, motor and sensory inn.
Roots: C6-T1 Cord: Lateral and medial Motor inn: wrist flexors (except flexor carpi ulnaris!!!!! *on exam*), pronator teres, pronator quadratus, lateral half of flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus/brevis, ABD pollicis brevis, opponens pollicis Sensory inn: cutaneous anterior lateral hand
Ulnar nerve: roots, cord, motor and sensory inn.
Roots: C8-T1 Cord: Medial Motor inn: flexor carpi ulnaris, medial half of flexor digitorum profundus, hand intrinsic muscles Sensory inn: 4th and 5th digits
Elbow flexion may be limited by what 2 factors
Soft tissue approximation of the biceps, Posterior capsule, elbow extensors, MCL tension.
Name two functions of the interosseous membrane
Space for muscle attachment, binds radius/ulna together, transmits force
What structures are taut and what are lax with flexion at HU joint?
Taut: MCL-posterior, posterior capsule, extensors, ulnar nerve Lax: flexors, anterior capsule
What structures are taut and what are lax with flexion at HR joint?
Taut: posterior capsule, lateral (ulnar) collateral ligament Lax: anterior capsule
What structures are taut and what are lax with extension at HU joint?
Taut: skin, flexors, anterior capsule, MCL-anterior Lax: extensors, posterior capsule
Stabilizers of the distal ulnar radial joint
Triangular complex: Pronator quadratus, tendon of ulnar, distal fibers of interosseous membrane
Articular disc covering the distal end of the ulna?
Triangular fibrocartilage TFCC
What is the primary stabilizer of the distal radioulnar joint?
Ulnocarpal complex, aka TFCC (triangular fibrocartilage complex), pronator quadratus, tendons of ECU, distal interosseous membrane -Articular disc + ulnar collateral ligament + dorsal and palmar capsular ligaments
What motions increase tension in anterior fibers of the MCL?
Valgus, extension, flexion
When is the medial collateral ligament susceptible to injury?
When fully extended elbow is forced into excessive valgus direction (often FOOSH injury) Ulnar nerve is also susceptible to injury with a valgus force
Posterior bundle of MCL most taut at what position
elbow flexion
What are the 4 articulations of the elbow forearm complex?
humeroulnar, humeral radial, proximal and distal ulnar radial
What are the three fossa on the distal humerus?
radial fossa, coronoid fossa, olecranon fossa
What motions increase tension in posterior fibers of the MCL?
valgus, flexion
What motions increase tension in radial collateral ligament (LCL)?
varus
What motions increase tension in ulnar collateral ligament (LCL)?
varus, flexion
