Glenohumeral Joint and rotator cuff tendinopathy

anatomy of GHJ

synovial joint between the large convex humeral head and small shallow concave glenoid fossa

resting position of GHJ

55 abducted and 35 horizontal adducted - 55 in scapular plane

close packed position of GHJ

full abduction and external rotation

capsular pattern of GHJ

Er, ABD, IR (most common for adhesive capsulitis)

flexion ROM at GHJ

180

extension ROM at GHJ

60

ER ROM at GHJ at 90 degrees abducted

90

ER ROM at GHJ at 20 deg shoulder abducted

60

IR ROM at GHJ at 90 degrees abducted

50-60

abduction ROM at GHJ

180

GIRD

internal rotation deficit of dominant shoulder when compared to nondominant shoulder

shoulder total rotation ROM concept

a deficit in IR combined with excessive ER on the dominant side - for an equal total ROM on both sides

rotator cuff musculature

supraspinatus, infraspinatus/teres minor, subscapularis, long head of biceps

supraspinatus concentric action

abduction

infraspinatus and teres minor concentric action

ER and horizontal abduction

subscapularis concentric action

IR

long head of biceps concentric action

small role with flexion

whats commonly impinged with anterior translation of humeral head

coracoacromial ligament - not acromion - impinging supraspinatus and LH biceps (not infra, teres major)

RC humeral head depression

line of pull depresses humeral head during shoulder elevation to counteract the upward pull of deltoid - dependant on the optimal posture of UR of scapula

it is useful to think of the role of muscles from

perspective of eccentric action - most musculotendinous injuries are a result of eccentric actions

rotator cuff interval

triangular space between the anterior margin of supraspinatus and superior margin of subscap, with coracoid process at its base

passive stabilizers of GHJ

small UR of glenoid with shoulder at rest, negative intraarticular joint pressure (any injection or surgery would eliminate this), bony congruency, GH ligaments provide end range stability to joint if muscles arent activated

active stabilizers of GHJ provide

mid-range and end-range stability/coordination/control of movement

active stabilizers of GHJ

rotator cuff musculature - LOP perpendicular to the joint surfaces and create large compressive forces when activated, ligaments participate in stability if tendons are active

while active stabilizers of GHJ are given credit for "dynamic stability"

works in concert with key passive stabilizers

rotator cuff injuries

due to tissue failure of the dynamic structures providing movement and dynamic stability to the GHJ (failure of active stabilizers)

laxity/dislocation/instability

due to structural or functional tissue failure of inert structures at end range (failure of passive stabilizers)

rotator cuff injuries and joint laxity may

co-exist in patient

rotator cuff tendinopathy risk factors

intrinsic/biological factors, or extrinisic/anatomical or biomechanical factors

intrinsic RC tendinopathy factors could include

vascularity, biology, mechanical properties, morphology, genetics, systemic diseases, smoking, nutrition

extrinsic factors RC tendinopathy could include

subacromial impingement or internal impingement

overuse RC tendinopathy

or disuse, wear/decrease in strength of tendons

types of RC tendinopathies

subacromial impingement, internal impingement, tensile overload

subacromial impingement

irritation of RC tendons due to excessive compression under coracoacromial arch - anterior section of acromion and coracoacromial ligament

subacromial impingement would anatomically affect

supraspinatus tendon and anterior portion of infraspinatus

subacromial impingement can be described at

outside-in or extra-articular wear of RC starting on subacromial surface

predisposing factors for subacromial impingement

inherent design of subacromial region, shape of acromion, spurs, hypovascularity of RC tendon

inherent design of subacromial region

supraspinatus is in a narrow space covered superiorly by acromion and coracoacromial lig., area of most impingement is at at 60 degrees of shoulder elevation

limited space in subacromial region provides

little ability to adapt to excessive upward displacement of HH during shoulder elevation (could occur with suboptimal function of RC and control of scapula)

knowing area of most impingement is at 60 degrees of shoulder elevation

stay below impingement with exercises to get good mechanics before moving to above 90 degrees

types of acromion shapes

type 1 - flat acromion, type 2 - curved acromion, type 3 - hooked acromion (radiograph needed to determine shape - consider if patient is not progressing well)

flat acromion

best prognosis with most patients getting better

hooked acromion

greater incidence of tendinopathy and RC tears, poor prognosis, nonsurgical rehab is less effective

spurs at subacromial space could occur at

under acromion from chronic inflammation and stress or under ACJ from OA

hypovascularity of rotator cuff tendon

critical zone near insertion on humerus tendon has limited blood supply, natural degenerative process of tendon due to poor regeneration capacity, decreased potential for healing

circulation of rotator cuff tendon is especially impaired when

tension is applied to tendon - occurs with arm at rest along side of the trunk

to promote circulation of rotator cuff tendon

support the arm in slight abduction (55 degrees) (supports healing)

functional predisposing factors of subacromial impingment

tightness of inferior portion of GHJ capsule or posterior shoulder, suboptimal posture or muscle function, excessive GHJ capsular laxity/hypermobility, excessive overhead tires

tightness of inferior portion of GHJ capsule

superior displacement of HH with shoulder abduction resulting in impingement of supraspinatus tendon under coracoacromial arch

tightness of posterior shoulder

superior/anterior displacement of HH with shoulder elevation, horizontal adduction, and IR resulting in impingement of supraspinatus tendon under coracoacromial arch

tight posterior capsule could also promote

anterior tilting and internal winging of scapula - reduce size of subacromial space

suboptimal posture of forward/protracted/rounded shoulder and thoracic kyphosis could cause

promotes IR, anterior tilt of scap, decreased UR of scap/promotes DR at rest, IR of humerus at rest - reduce size of subacromial space

poor posture, combined with excessive thoracic kyphosis and forward/protracted/rounded shoulder can be due to or lead to

weakness of trunk extensors and scapular retractors, tightness of pec major and minor, stiffness of thoracic spine

chronic poor posture with protracted shoulders leads to

tight posterior capsule/shoulder region

weakness of rotator cuff musculature can

weakness of RC can result in excessive upward displacement of humeral head during shoulder elevation

poor dynamic stabilization/muscle imbalance between GHJ internal and external rotators

effects optimal centralization and control of humeral head during shoulder motion

optimal strength ratio for Er/IR

68-75% - want ER to be 70% as strong as IR

weakness of scapular stabilizers and upward rotators of scapula lead to

inadequate UR, posterior tilting and ER of scapula during elevation - could even lead to downward rotation, anterior tilt and IR in during early phase of shoulder elevation (scapular dyskinesia)

DR, anterior tilt and IR of scapula lead to

reduced subacromial space and inefficient action of RC musculature

excessive GHJ capsular laxity/hypermobility

increased demand of dynamic stabilizers of shoulder, poor dynamic stabilization of HH

excessive mobility may be due to

congenital laxity, acquired laxity, or trauma via subluxation or dislocation

excessive overhead activities

address volume and quality of movement (consider how fatigue of workers could lead to increased upward migration of HH with shoulder elevation)

lifestyle predisposing factors for subacromial impingement

disuse, smoking

internal impingement/posterior glenoid rim

compression/shear of rotators cuff tendon against posterior-superior glenoid labrum/rim

internal impingement affects

infraspinatus and posterior aspect of supraspinatus

internal impingement is inside-out wear of RC

starts on the articular side of the tendon

articular surface of the RC is slow to heal

due to hypovascularity

posterior glenoid impingement occurs with

ER in 90 degrees abduction, pain is felt posterior/superiorly

functional predisposing factors for internal impingment

OH athletes due to excessive ER of shoulder with excessive anterior translation of HH in 90/90 (acquired laxity), excessive GHJ horizontal abduction when pitching, scapular dyskinesia, RC weakness, GHJ IR deficits,

excessive GHJ horizontal abduction

pinches posterior aspect of GHJ - translates HH anteriorly

scapular dyskinesia

without optimal scapular stabilization, posterior deltoid activation can cause scapular IR and pinch posterior aspect

scapular internal rotation are essentially

GHJ horizontal abduction

rotator cuff weakness/posterior cuff muscle weakness can lead to

poor dynamic stabilization keeping HH centralized, and posterior shoulder pain

posterior shoulder pain could be due to

internal impingement and tensile overload

pain with cocking

internal impingement

pain at release

tensile overload

GHJ internal rotation deficits

posterior shoulder tightness with twisting of capsule can promote superior/anterior displacement of HH with GHJ ER - hyperplasia of posterior capsule and neuromuscular to repetitive throwing

external/subacromial impingement summary

occurs as early as 60 degrees of arm elevation, extraarticular lesion primarily at supraspinatus

internal impingement of posterior glenoid rim summary

occurs at higher levels of arm elevation above 140 degrees with GHJ ER, intraarticular lesion primarily at infraspinatus and posterior edge of supraspinatus

tensile overload

repetitive high tensile eccentric stresses placed on tendons of cuff musculature causing stress failure in mid-substance of the tendon

tensile overload is primarily associated with

posterior rotator cuff tendons of infraspinatus and teres minor, can co-exist with internal impingement

tensile overload damage occurs in

mid-substance of the tendon, not at front or back

injury types for tensile overload

throwing/OH sports, middle age "week-end athlete," heavy lifting/repeated high tensile load

functional predisposing factors to tensile overload

excessive GHJ capsular laxity/hypermobility, excessive OH and/or lifting activities

external impingement secondary to hypomobility of GHJ

inferior and potentially overall capsule (poor posture, golf or doing OH), posterior shoulder/capsule (OH athlete)

external impingement secondary to hypermobility of the GHJ

acquired (OH athletes) or congenital (younger females with excessive flexibility, poor posture/overall weakness)

external impingement secondary to poor muscle coordination/balance

rotator cuff musculature (middle age weekend athlete, factory workers), or scapulothoracic musculature with scapular dyskinesia (weak RC muscles, young females and poor posture)

internal impingement is primarily attributed to

overhead activities requiring 90/90 position

internal impingement secondary to hypermobility of GHJ

acquired/OH, potentially combined with posterior shoulder tightness

tensile overload common predispositions

OH athlete, hypermobility

calcific tendinopathy most tyically occurs in

supraspinatus and/or infraspinatus