ICL 4.0: Upper Extremity Arthrology

Question 1

describe a synovial joint

Answer 1

the bones are covered with articular/hyaline cartilage at the ends

in between the cartilage is synovial fluid produced from the synovial membrane

and encasing the whole joint is a fibrous membrane; the fibrous membrane is an intrinsic ligament which means it’s a weak stabilizer of the joint

Question 2

what is the sternoclavicular joint?

Answer 2

it’s formed by the juncture of the clavicle with the upper bilateral aspect of the manubrium and the cartilage of the 1st rib

it’s a synovial joint!

the interarticular disc divides the joint space into two subspaces which allows for significant motion that wouldn’t be possible otherwise

Question 3

what is the function of the sternoclavicular joint?

Answer 3

acts as a strut for keeping the shoulder away from the chest to give the upper extremity the maximum freedom of motion

*the strength of the SC joint depends on ligaments and its articular disc!

Question 4

what happens if you injure your sternoclavicular joint?

Answer 4

if you dislocate your clavicle backwards from blunt force trauma to the chest and rip the intrinsic ligaments your clavicle would move backwards

this is in the direction of the thoracic outlet which has blood vessels and your trachea so you could compromise neural, respiratory and vascular structures contained in the thorax

Question 5

what is the acromioclavicular joint?

Answer 5

where the distal end of the clavicle meets the medial edge of the acromion process of the scapula

it allows scapula to remain in contact with clavicle as scapula slides over thoracic wall

this joint is fibrous at birth then gets a synovial disc in adulthood

it’s one of the 4 joints that makes up the shoulder

Question 6

which ligaments are part of the acromioclavicular joint?

Answer 6

1. intrinsic ligaments = weak = acromioclavicular ligament
2. extrinsic ligaments = strong = coracoclavicular ligaments

the coracoclavicular ligaments are the trapezoid ligament and the conoid ligament – both attach from the clavicle to the coracoid process of the scapula = they are not actually in contact with the joint!! they are just support ligaments of the AC joint

Question 7

what is the function of the coracoclavicular ligaments?

Answer 7

they contribute to horizontal stability, making them crucial for preventing superior dislocation of the AC Joint

the coracoclavicular ligaments are the trapezoid ligament and the conoid ligament – both attach from the clavicle to the coracoid process of the scapula = they are not actually in contact with the joint!! they are just support ligaments of the AC joint

Question 8

how do you classify how severe an acromioclavicular joint injury is?

Answer 8

scale of 1-6

1 just means that you’re straining the intrinsic fibers and they get a little inflamed (acromioclavicular ligament)

once you get to 3 you have more of a complete tear of intrinsic ligaments and you’re also putting stress on the extrinsic ligaments which means you start to lose stability of the joint (coracoclavicular ligaments)

Question 9

what is the function of the coracoacromial ligament?

Answer 9

it attaches from the acromion to the coracoid process of the scapula

it is NOT a stabilizer of the AC joint since it attaches to two points on the same bone (the scapula)

however it DOES stabilize the glenohumeral joint against major superior displacements such as falling on an out stretch arm – keeps your humerus from going into your neck when you fall and wipe out on ice

Question 10

what is the scapulothoracic joint?

Answer 10

physiologically it is NOT a true anatomical joint

it’s in-between the rib cage and the scapula

it is an articulation of the anterior aspect of the scapula on the posterior thorax

Question 11

what is the glenohumeral joint?

Answer 11

aka the shoulder joint!

it’s the synovial joint between the head of the humerus and the glenoid fossa of the scapula

the intrinsic muscles surrounding this joint are weak so it’s the muscles of the rotator cuff that give this joint durability

Question 12

what happens if you have a fracture at the surgical neck of the humerus?

Answer 12

you could damage the axillary nerve that’s behind it

Question 13

what is the axillary recess? what condition is associated with it?

Answer 13

part of the intrinsic ligaments of the glenohumeral joint that allows for abduction to occur without capsule deformation

it’s what gives the shoulder such a large ROM!!

when the inner surfaces of the recess stick together, the humerus cannot abduct - this condition is called “adhesive capsulitis” or “frozen shoulder

Question 14

what are bursa?

Answer 14

fluid filled sacs that protect muscles and tendons from the rigors of bone

if a tendon or muscle were to just continuously rub on bone it would get inflamed and eventually tear

Question 15

what are the two significant bursa in the shoulder?

Answer 15

1. subscapularis bursa (communicating)

2. subacromial/deltoid bursa (non-communicating)

Question 16

what is the subscapularis bursa?

Answer 16

it’s located between the tendon of the subscapularis muscle and the NECK of the scapula

it’s considered an extension with of the synovial sac and a frequent entry point for surgery of the shoulder** – once you’re in the subscapularis bursa you’re in the shoulder joint = communicating joint

Question 17

what is the subacromial and subdeltoid bursa?

Answer 17

they sit between the acromion and the supraspinatus tendon

both DO NOT communicate with shoulder joint unless there is a complete tear through the supraspinatus tendon

Question 18

what is the glenoid labrum?

Answer 18

a fibrocartilage ring that encircles the rim of the glenoid cavity. of the scapula

it deepens the socket of the glenoid fossa to allow of the head of the humerus to stay intact with the cavity and articulate with the cavity

so if there’s a glenoid labrum tear your humerus will start to come out of its socket!!

Question 19

what gives the rotator cuff its stability?

Answer 19

muscles!!

1. supraspinatus,
2. infraspinatus
3. teres minor
4. subscapularis

these four tendons blend into the superior surface of the glenohumeral joint capsule and the inferior surface of the subacromial bursa

notice that the bursa is between the tendons and acromial process of the scapula

Question 20

when you dislocate your shoulder what should you be worried about?

Answer 20

impinging on your axillary nerve

less often the radial nerve can be injured in shoulder dislocations which will result in wrist drop

Question 21

which joint is responsible for elbow flexion and extension?

Answer 21

flexion and extension motion at the elbow is determined by the relationship of the ulnar trochlear notch joint surface to the humeral trochlea joint surface

Question 22

which joint is responsible for pronation/supination?

Answer 22

pronation-supination motion at the elbow is determined by radial motion at the proximal and distal radio-ulnar joints

Question 23

what is the annular ligament?

Answer 23

the head of the radius is constantly moving inside the circular annular ligament when you are supinating/pronating

it also prevents the radial head from inferior dislocation

this is why parents shouldn’t swing their kids by holding on each arm because you could inferiorly dislocate the head of the radius from the annular ligament!

Question 24

what are the 3 intrinsic ligaments of the elbow?

Answer 24

1. ulnar collateral (3 parts)
2. radial collateral
3. annular

Question 25

what is the interosseous membrane?

Answer 25

it’s the membrane between the radius and the ulna

some people consider it a fibrous joint

its function is to transmit distal-to-proximal force from hand, to the radius at the wrist, to the interosseous membrane, to the ulna, to the humerus at the elbow (like when you fall and land on your hand = FOOSH)

the interosseous membrane also compartmentalizes the forearm into anterior and posterior regions; this is important because muscles in each compartment work together to do the same function –> anterior region does flexion and posterior region does extension

Question 26

what are the 3 functions of the interosseous membrane?

Answer 26

it’s the membrane between the radius and the ulna

1. attachment point for muscles
2. compartmentalization of the forearm
3. prevents radial fracture because without it the radius would shove into the distal humorous during a FOOSH

Question 27

which bone moves during supination/pronation?

Answer 27

radius

the ulna is passive!!

at the proximal radioulnar joint the head of the radius spins relative to the ulnar notch so that the radius rotates

at the distal radioulnar joint the “spin” of the radial head during pronation forces the ulnar notch of the radial base to pivot over the ulnar head which places the distal end of the radius anterior to the ulna instead of lateral to it

Question 28

what separates the distal radioulnar joint from the carpals?

Answer 28

TFC = triangular fibrocartilage

the TFC is attached to both the ulna and the radius but is nOT part of the wrist joint

its function is to separate the ulna from articulating with the proximal row of carpal bones

Question 29

what is the wrist joint?

Answer 29

it’s a single synovial space that separates the base of the radius from the proximal row of carpal bones = scaphoid, lunate and triquetrum (the pisiform doesn’t contribute)

Question 30

how do you palpate the scaphoid?

Answer 30

palpate snuff box then do ulnar deviation

Question 31

how many intercarpal joints are there?

Answer 31

17

Question 32

which bones are in the proximal carpal row?

Answer 32

scaphoid
lunate
triquetrum
pisiform

Question 33

which bones are in the distal carpal row?

Answer 33

trapezium
trapezoid
capitate
hamate

Question 34

what is the joint between the proximal row of carpals and the radius?

Answer 34

radoiocarpal joint

Question 35

what is the joint between the proximal and distal row of carpals?

Answer 35

midcarpal joint

allows for ulnar and radial deviation

Question 36

what is the joint between the distal row of carpals and the metacarpals?

Answer 36

carpometacarpal joint

Question 37

what is found in-between the carpal bones?

Answer 37

interosseous ligaments

when you look at an x-ray the spacing between carpal bones should be equal if the ligaments are intact and not torn

Question 38

what is special about the carpometacarpal joint of the thumb?

Answer 38

the carpal-metacarpal joints are synovial, with planar joint surfaces; these allow very limited flexion and rotation

the exception is the thumb! the 1st carpometacarpal joint
(a.k.a trapezio-metacarpal or Kelgren’s Joint) of the thumb appears to be isolated

the thumb can do abduction, adduction, extension, flexion, opposition and reposition

however this means it’s also involved in osteoarthritis…

Question 39

what are the metacarpophalangeal joints?

Answer 39

aka the knuckles

allow for motion of flexion-extension and medial-lateral deviation (adduction-abduction) of the proximal phalanx

Question 40

what’s the point of the creases in your palm?

Answer 40

they’re where your skin anchors to the fascia below!

surgeons also use it for a guiding tool

Question 41

how are the long tendons in the hands, fingers and feet protected?

Answer 41

bursae!

the bursa wraps all the way around the tendon = tendon sheath

except there is an opening in the bursa called the mesotendon – vascular structures can come through the mesotendon opening to provide blood supply to the tendons

Question 42

what is tendonitis?

Answer 42

“tendonitis” is not used to describe a tendon inflammation, but rather a tendon sheath inflammation

aka the tendon itself isn’t inflamed, it’s the inflammation of the bursa fluid going around the tendon that’s inflamed

it should more properly be called tenosynovitis