glenohumeral joint Flashcards
glenohumeral joint classifications
multiaxial ball-and-socket
enarthrodial
glenohumeral joint components
joint cavity
fibrous capsule
synovial membrane
glenoid labrum role
thickens cavity, deepens socket to improve articular fit (thick periphery, thin at center)
problems with joint
little congruity between ball and socket
Shoulder joint is set up such that a ball is sitting on a plane that is angled forward and down
Like a golf ball sitting on a tee that is lying on is side -> Ball is constantly trying to roll/slide off the Glenoid
glenoid labrum role
slightly enhances stability by deepening the concavity of the fossa
serves as buttress to excessive humeral head translation
glenoid labrum injuries
injured with sudden overhead movements and with trauma
supra-humeral space
Deep=Long-head of Biceps tucked up under fibrous capsule, Fibrous portion of Capsule, & Supraspinatus Tendon (Most easily & commonly injured rotator cuff)
Superficial=Subacromial/Subdeltoid Bursa and Coracoacromial Ligament
glenohumeral ligaments
superior gh ligament
middle gh ligament
inferior gh ligament
coracohumeral ligament
glenohumeral ligament roles
provide stability
usually blend together, cannot separate out to identify/not all people possess all of these ligaments
superior gh ligament role
Thicken Anterior Capsule
Help to protect against anterior dislocations
coracohumeral ligament role
Won’t allow humeral head to be displaced inferiorly (pulled downward)
typical dislocations
usually inferior or anterior
posterior not usually seen (falling on outstretched arm)
ligament tension
Ligaments are quite lax until extreme ranges of motion reached due to wide range of motion involved
ROM for each motion
difficult to measure exactly due to accompanying shoulder girdle movement
abduction ROM
180 degrees
adduction ROM
0 degrees, 75 degrees anterior to trunk
extension ROM
40 to 60 degrees
flexion ROM
90 to 100 degrees
flexion/extension limitations
must do motions in anatomical position
external rotation required to clear shoulder, internal rotation with movement has limit
internal / external rotation ROM
70 to 90 degrees in both planes [horizontal and vertical]
horizontal abduction ROM
45 degrees
horizontal adduction ROM
135 degrees
anatomical design components contributing to injury
shallowness of glenoid fossa
laxity of ligamentous structures
lack of strength & endurance in muscles
dislocation types and frequency
anterior or anteroinferior glenohumeral subluxations & dislocations – common
posterior dislocations – rare
posterior instability problems somewhat common
SITS muscles
subscapularis
supraspinatus
infraspinatus
teres minor
SITS design and role
attach to the front, top & rear of humeral head
point of insertion enables humeral rotation
vital in maintaining humeral head in correct approximation within glenoid fossa while more powerful muscles move humerus through its wide range of motion
Glenohumeral internal rotation deficit (G I R D)
difference in internal rotation range of motion between an individual’s throwing & nonthrowing shoulders
overhead athletes with a G I R D of greater than 20% had a higher risk of injury
