injuries to the glenoid labrum of the glenohumeral joint usually have a traumatic origin , and more rarely a degenerative etiology . the overwhelming majority of lesions involve the anterior part of the labrum , as within the group of shoulder instabilities , the anterior instability dominates . most commonly , the joint instability is a result of previous trauma . the trauma causes irreversible damage to the labral - ligamentous complex , which can predispose to further joint dislocations ( not uncommonly recurrent or even habitual ones ) . other causes of instability may be associated with generalized flaccidity of the joints , neuromuscular disorders and muscle dysfunction , as well as acquired or congenital bone defects , for example glenoid cavity hypoplasia . untreated instability is dangerous for the joint , as it leads to damage of cartilage and progression of degenerative changes . moreover , the resulting functional limitations of the upper limb cause the patient significant discomfort . this issue is all the more relevant , as it affects mostly young and active persons . a second group of labral pathologies , not directly associated with shoulder instability , are injuries to the superior labrum , known as slap ( superior labrum anterior - posterior ) lesions , which occur in 3.96% of cases . among other pathologies , the initial imaging modality for diagnosing shoulder pathologies should be radiography ( x - ray ) . on the basis of x - rays , it is possible to assess the bony anatomy of the shoulder and to confirm or rule out the presence of traumatic or degenerative changes within the bones . whereas for the evaluation of the soft tissues of the shoulder , magnetic resonance imaging ( mri ) is recommended , and is considered the imaging method of choice . in patients with clinically diagnosed shoulder instability or suspicion of a slap tear , mri with intra - articular administration of contrast medium ( mr arthrography ) is used for better assessment of the glenoid labrum and the capsular - ligamentous complex . the benefits of mri include excellent tissue contrast along with high spatial resolution , and lack of exposure to radiation . if there are contraindications to mri or the study is unavailable , it may be substituted by computed tomography with intra - articular contrast dye injection ( ct arthrography ) , which has a comparable to mr artrhrography diagnostic value in detection of labral injuries . ct also allows for precise imaging of the bony structures with the possibility of assessing the glenoid cavity morphology on the basis of multiplanar and 3-dimensional ( 3d ) reconstructions . the ct study is especially indicated in the pre - operative diagnostics of bankart lesions with fractures of the glenoid . the main downside of ct is the exposure of the patient to radiation . compared to mri , ct has a worse ability to precisely image the soft tissues of the joint , including the rotator cuff . what could be the role of ultrasound ( us ) in the diagnosis of labral pathologies of the shoulder ? since many years , the us examination has had an established role in the diagnostics of musculoskeletal pathologies . important benefits of us include its wide availability , lack of contraindications , and the possibility of a dynamic assessment . a relevant disadvantage of us is the large dependence on the experience of the examiner resulting in a subjective assessment , as well as the quality of the ultrasound equipment . among shoulder pathologies , us has been widely used in evaluating the rotator cuff and other muscles , shoulder impingement syndromes , particularly subacromial impingement , subacromial - subdeltoid bursitis , inflammatory changes , compression neuropathies and acromioclavicular and sternoclavicular joints injuries . some papers also indicates the utility of us in assessing the glenoid labrum . despite these latter reports , several years of the authors clinical experience indicate that us can image most parts of the glenoid labrum ( see part i of the article ) . this imaging technique also allows for the visualization of other changes associated with a shoulder dislocation , such as the impaction injuries of the humerus ( hill - sachs lesion , mclaughlin lesion ) or loose intraarticular bodies . when evaluating the glenoid labrum , it is always recommended to compare findings with the healthy side . the following us features confirm a pathology of the labrum : permanent displacement of the labrum onto the external part of the glenoid;labral instability in the dynamic examination;lack of the labrum in the anatomical position;hypoechoic zone at the base of the labrum , > 2 mm in width;residual or swollen labrum;paralabral cyst(s ) . permanent displacement of the labrum onto the external part of the glenoid ; labral instability in the dynamic examination ; lack of the labrum in the anatomical position ; hypoechoic zone at the base of the labrum , > 2 mm in width ; residual or swollen labrum ; lesions of the posterior part of the glenoid labrum are rather uncommon . they can result from trauma ( posterior dislocation of the shoulder ) , degenerative changes as well as internal impingement syndromes ( the posterosuperior or posterior ones ) . the posterior shoulder dislocations mainly cause injury to the posteroinferior part of the labrum . the possible post - traumatic findings include injuries similar in appearance to those of the bankart - type (  reversed bankart  , polpsa type ) with or without fracture of the glenoid rim . injuries to the posterior labrum may coexist with lesion of the anterior labrum , in cases of multidirectional instability of the shoulder . in internal impingement syndromes , the labrum is most commonly affected in its posterosuperior or superior parts ( slap tears ) . a sure sign of labral pathology in the us examination is a labral avulsion and displacement onto the external aspect of the glenoid , or a lack of the labrum in its anatomical position ( fig . the depiction of pathologies is facilitated by the increased amount of joint fluid . in posterior instability , the head of the humerus moves more posteriorly ,  sticking out  of the glenoid cavity to a larger extent than on the healthy side . the assessment should also be performed in a patient - provoked subluxation of the shoulder if it is possible . lesions of the posterior glenoid labrum : a. an irregular , decreased in size labrum ( arrows ) ; b. a labrum avulsed and displaced onto the glenoid ( arrows ) ; h  head of the humerus , moved backwards in relation to the glenoid ( b ) , isp  the infraspinatus muscle ; joint fluid ( * ) to the group of labral pathologies belong paralabral cysts , which most often occur in the posterior and superior parts of the shoulder joint ( fig . the mechanism of paralabral cyst formation is similar to meniscal cysts , and is related to degenerative changes and/or small tears of the labrum , through which the joint fluid passes outside the joint to form paralabral collections . large cysts may be localized in the area of the scapular neck and extend towards the supraspinous or infraspinous fossa , causing compression ( entrapment ) of the suprascapular nerve as it runs through the supraglenoid and the spinoglenoid notch of the scapula ( fig . it is also possible to puncture the cyst under us guidance , aspirate its content and inject steroids into its lumen . paralabral cysts in the posterior region of the shoulder : a. a small cyst ( arrow ) of the labrum ( * ) with a small fissure representing labral tear ( arrowheads ) ; b. a larger cyst ( arrows ) near the labrum ( * ) ; c. a large paralabral cyst ( arrows ) in the spinoglenoid notch ; gle  the glenoid , h  the head of the humerus lesions of the anterior labrum are the most common pathologies of the capsular - ligamentous - labral complex . they are usually the result of an anterior dislocation of the shoulder , and primarily affect the anteroinferior part of the labrum . this group contains bankart lesions , with or without fractures of the glenoid rim (  bony bankart  ) or so - called bankart - variants ( alpsa , perthes , and glad lesions ) . the labral injuries are often accompanied by post - traumatic changes to the joint capsule and glenohumeral ligaments ( especially the inferior one ) , which may be sometimes the dominant element of the injury to the entire complex ( ex . the authors experience indicates , that the most common pathology seen on us in patients after anterior shoulder dislocation is a permanent displacement of the anteroinferior part of the labrum ( sometimes along with the anterosuperior part ) onto the external contour of the glenoid , with an altered architecture of the entire capsular - labral complex ( fig . 3 ) . the avulsed labrum along with the injured capsular - labral complex , with time undergoes healing and scarring , and it may sometimes re - attach to the glenoid in a non - anatomical position . in the case of acute injury , with a hematoma present , ultrasound can show fluid penetrating between the injured structures . in the authors opinion , a characteristic finding indicating an injury of the capsular - labral complex , are calcifications  small or large , single or multiple  located near the external aspect of the glenoid , readily depicted by us . they may represent avulsed bone fragments ( usually not visible on the x - ray or not recognizable on mri images ) or be calcified periosteal scars ( fig . 3 ) . this sign is highly specific for a bankart injury . in the case of small fractures of the glenoid rim , a  v-shaped deformity on the external contour of the glenoid a. injury to the anterior capsular - labral complex ( arrowheads ) with thickening of the capsular structures and displacement of the avulsed labrum ( * ) on the external aspect of the glenoid ; a small post - traumatic calcification ( arrow ) . b. an avulsed fragment of the glenoid ( arrow ) along with the detached labrum ( * ) ; gle  the glenoid , h  the head of the humerus , ssc  the subscapularis muscle bankart lesion with a typical  v-shaped deformity of the external aspect of the glenoid ; gle  the glenoid , h  the head of the humerus , the damaged labrum ( * ) a second sign indicative of labral injury , is instability of the labrum in the dynamic examination . during internal rotation of the upper extremity , the head of the humerus presses upon the labrum with the joint capsule being relaxed , causing a minor turning of the labrum in the anterior direction . sometimes the joint capsule may be seen a little sliding against the labrum . in the case of post - traumatic changes without a permanent displacement of the labrum ( for example in perthes injuries ) , the labrum is properly located when the upper limb is in the intermediate rotation . in contrast , when the limb internally rotates the labrum clearly deviates or even displaces in the anteromedial direction , while the opposite rotation returns the labrum into its initial position ( fig . 5 ) . in authors opinion , it is more difficult to obtain a distinct  dislocation  of the labrum in external rotation of the limb in 90 abduction , even though this is the standard position used for the clinical examination ( anterior apprehension test ) . the dynamic examination of the labrum may be difficult or even impossible to do in cases of acute injuries , due to limited mobility of the joint secondary to pain . in patients with chronic anterior joint instability , a more prominent anterior protrusion of the humeral head with respect to the glenoid may be observed on ultrasound ( anterior subluxation ) . when the probe is applied from the posterior aspect of the joint , the  regression  of the humeral head relative to the glenoid 's contour will be seen . the us study may also be used to assess the stability of the glenoid labrum after a surgical repair . injury to the anteroinferior part of the labrum ( perthes type lesion ) : a. the capsular - labral complex ( arrows ) with the non - displaced labrum ( thick arrow ) ; the upper limb in intermediate rotation ; b. in internal rotation , the labrum ( along with the overlying joint capsule ) ( arrows ) gradually displaces onto the glenoid under the pressure of the humeral head ; c. the labrum completely dislocated onto the external aspect of the glenoid ; h  the head of the humerus , gle  the glenoid another pathological finding is the absence of the labrum in its anatomical position . in this case , a contour of a  naked  glenoid is visible , and barely discernible fragments of the labrum may be found on the external surface of the glenoid . the assessment is facilitated by the increased amount of fluid in the joint ( fig . some developmental variants , especially those with glenoid labrum hypoplasia , should be kept in mind . labral hypoplasia may affect the anterior and posterior parts of the glenohumeral joint , but it is most often found in the anterosuperior region , as part of the so - called buford complex ( occurring in approximately 6% of cases )  above the region of the labrum most affected by traumatic injuries accompanying anterior instability of the shoulder ( fig . 7 ) . a lack of a labral echo in the expected position : the  empty  edge of the glenoid ( thick arrow ) ; irregular contours of the anterior capsule from the joint side  post - traumatic changes ( thin arrows ) ; h  the head of the humerus , gle  the glenoid the buford complex : a. a hypoplastic anterosuperior labrum with the thick middle glenohumeral ligament resembling the labrum ( arrow ) ; a flattened outline of the glenoid ; b. on the contralateral side , in the same region , a normal labrum is visible ( * ) along with the more oblique outline of the glenoid ; h  the head of the humerus , gle  the glenoid a sign of labral injury described in the literature is the presence of a hypoechoic area at the base of the labrum , > 2 mm in width ( compared to the normal transitional fibrocartilage of < 2 mm in width ) . this finding may be observed in injuries with partial avulsion of the labrum from the glenoid ( fig . thus the usefulness of this criterion is disputable , although along with instability of the labrum in the dynamic examination , it definitely indicates an injury . a hypoechogenic area ( arrows ) at the base of the labrum ( * ) indicating the detachment from the glenoid ; the injury also affects the attachment site of the joint capsule ( arrowheads ) ; h  the head of the humerus , gle  the glenoid , ssc  the subscapularis muscle as for degenerative changes of the labrum , they are manifested by a heterogenous echogenicity as well as a decrease or increase in size ( edema ) of the glenoid labrum . irregular boundaries of the labrum are found even in normal conditions , so they should not be considered pathological . it should be remembered , that not visualizing any labral changes in the us study , both with respect to labral morphology as its stability , does not exclude the presence of pathology when such is suggested in the clinical examination . in these cases injuries to the superior part of the glenoid labrum ( slap lesions ) represent the labral pathology not directly related to shoulder instability ) . they often affect people who perform sports which involve overhead activity ( overhead throwers )  baseball , basketball , volleyball , javelin throw , disc throw , etc . , as well as swimming or weight lifting . they also occur in those doing manual labor with frequent excessive abduction and external rotation , and then have the character of fatigue injury . sometimes slap lesions may be caused by isolated trauma , for example after a fall on an extended extremity or from pulling the limb upwards . many types of slap injuries have been described , based upon the morphology and extent of changes , whose classification  even based upon mri  is still challenging . there is a lack of published reports on the use of us in the assessment of slap lesions . according to the authors , ultrasound may also be used in the diagnosis of slap injuries to show the instability of the labrum or the superior biceps - labral complex . in the dynamic examination , sometimes it is possible to visualize even smaller lesions , without clear signs of instability or with only minor instability of the labrum ( fig . lesion of the superior part of the labrum ( slap tear ) . the dynamic us study , with the probe applied anterior to the clavicle , shows the phases of the labrum 's displacement ( arrows ) onto the upper part of the glenoid : a. the labrum in the anatomical position ; b. flattening of the labrum with partial displacement onto the glenoid ; c. complete  inversion  of the labrum onto the upper surface of the glenoid ; h  the head of the humerus , gle  the glenoid , cla  acoustic shadow of the clavicle , ssp  the tendon of the supraspinatus muscle slap lesions . the us examination in 3 different patients , with probe applied right posterior to the clavicle . fissures representing labral tears ( arrows ) : with an oblique course ( a ) and a vertical one ( b ) ; irregular lesion / degeneration of the superior labrum ( arrows ) ( c ) ; h  the head of the humerus , gle  the glenoid , ac  the acoustic shadow of the acromion , ssp  the supraspinatus muscle based on own studies , the authors are convinced of the utility of ultrasound in the diagnosis of pathologies of the glenoid labrum . an important benefit of us is the possibility of a dynamic assessment and simultaneous comparison of the examined side to the healthy one . . the us study may be useful in the diagnostics of slap injuries , but this still remains controversial and requires further evaluation .
labral pathologies of the glenohumeral joint are most commonly caused by trauma . 
 the majority of lesions affect the anterior part of labrum , resulting from much higher frequency of anterior shoulder dislocations over posterior ones . 
 another subgroup of labral lesions , not directly related to joint instability , are slap tears . 
 other findings include degenerative changes of labrum and paralabral cysts . 
 diagnostic imaging is crucial for making a decision regarding operative treatment . 
 apart from a standard x - ray examination , the imaging mainly relies on magnetic resonance or computed tomography arthrography . based on their own experience , 
 the authors propose the use of ultrasound in the assessment of labral tears of the glenohumeral joint . 
 different signs indicating labral pathology may be discovered and assessed during ultrasound examination . 
 they include permanent displacement of the labrum onto the glenoid , labral instability during dynamic examination , lack of the labrum in the anatomical position , hypoechoic zone at the base of the labrum > 2 mm in width , residual or swollen labrum as well as paralabral cyst(s ) . 
 the most frequent appearance of labral pathology is displacement of the anteroinferior labrum onto the external aspect of the glenoid typically seen after anterior shoulder dislocation . 
 the another most important us feature is labral instability while dynamically examined . 
 the swelling or reduced size of the labrum usually indicates degeneration . 
 this article presents sonographic images of selected labral pathologies .