The Infraspinatus is one of the four muscles that comprise the Rotator Cuff which collectively are the primary dynamic stabilisers of the Glenohumeral Joint and consequently, The Shoulder Girdle . The Infraspinatus spans from the posterior (dorsal) surface of the Scapula to a prominence on the Proximal Humerus , known as the Greater Tubercle.
The Infraspinatus is a triangular Muscle with a thick belly that accounts for the majority of theInfraspinous Fossa, a surface on the posterior Scapula which serves as the muscles origin. Muscular fibres arise from the medial two-thirds to three-quarters of the Infraspinous Fossa, while tendinous fibres arises from the ridges of the fossa and the deep layers of theInfraspinous Fascia which envelops the muscle (SOURCE-22+23). Although variably reported, the muscle belly is often is often described to have three distinct partitions based on Fascia l compartmentalisation and fibre orientation (SOURCE-26+27):
Superior Partition - fibres that arise from the Spine of Scapula and course horizontally
Middle Partition - fibres that arise from the Medial Border of Scapula and Infraspinous Fossa and course superolaterally
Inferior Partition - fibres that arise from the inferior third of the Medial Border of Scapula and Infraspinous Fossa and the deep surface of the Infraspinous Fascia and course superolaterally
As fibres course towards the lateral edge of the Scapula Spine they converge to form a Tendon which passes over the Scapula and crosses the posterior shoulder. Tendinous insertion is made on the middle facet of the Greater Tuberosity of Humerus with a large footprint that is second in size only to the Subscapularis (SOURCE-22+23). This tendon fuses with the Supraspinatus Tendon to form a single integrated sheet (SOURCE-23). This sheet then courses anteriorly over the Rotator Interval , with the Infraspinatus portion of the sheet blending with the Subscapularis Tendon (SOURCE-23). The Infraspinous Fascia that envelops the Infraspinatus also covers the superior surface of Teres Minor at their lateral end which serves to coordinate and distinguish these muscles (SOURCE-22+23)
The Infraspinatus receives nervous innervation from the Suprascapular Nerve , from C5 and C6 Nerve Roots (SOURCE-22).
The Infraspinatus, a significant component of the rotator cuff, exhibits a parallel Muscle Architecture , characterised by an absence of pennation (0º angulation). Its muscle fibres are notably long, being very close to its overall muscle length. This parallel design enables efficient force transmission along the line of muscle pull and suggests an emphasis on generating movement across a greater range of motion and at higher velocities. As one of the larger Rotator Cuff muscles, the Infraspinatus possesses a substantialPhysiological Cross-Sectional Area (PCSA)which underscores its capacity to generate significant force crucial for its role in shoulder external rotation and dynamic stability. While certain metrics are heavily contingent on the population evaluated and measurement methodology, the following has been reported:5 cadavers, average age of ~73 years (SOURCE-7):
PCSA - 5.89 ± 0.32 cm²
Muscle Length - 134 ± 5mm
Muscle Fibre Length -124 ± 5mm
Pennation Angle - 0º
Muscle Mass - 76 ± 5g
MRI of 10 subjects (5 female, 5 male) 24-37 years, 158-188cm tall and a bodyweight of 50-86kg (SOURCE-8):
PCSA - 11.9 ± 4.2 cm²
Total Muscle Volume - 118.6 ± 46.7 cm³
Total Muscle Length - 14.0 ± 1.0 cm
The Infraspinatus appears to be less anatomically variable than other Rotator Cuff muscles, although it has been described to be fused with the Teres Minor on occasion (SOURCE-22).
Collectively the Rotator Cuff affords dynamic stability to the Glenohumeral Joint , in part through its regulation of the arthrokinematics and contraction on the Glenohumeral Joint Capsule (as described on its page) (SOURCE-21). Like the Subscapularis and Teres Minor , the Infraspinatus has an inferiorly directed translation force on the Head of Humerus which offsets the notable superior pull over the Deltoid during arm elevation and helps prevent impingement during the second half of the movement (SOURCE-21). While not a primary action of the Infraspinatus, it contributes ~10% of the total GH Joint - Abduction Torque (SOURCE-4). The posterior draw of the Infraspinatus also forms a stabilising anteroposterior force coupling with the anterior draw of Subscapularis (SOURCE-22).
In terms of movement, the Infraspinatus, Teres Minor and Posterior Deltoid facilitate GH Joint - External Rotation (SOURCE-21). Through its attachment to the Posterior Glenohumeral Joint Capsule , contraction of the Infraspinatus during this GH Joint - External Rotation pulls the posterior capsule taut which centers and stabilises the Head of the Humerus (SOURCE-21). The significant contribution the Infraspinatus makes to GH Joint - External Rotation drops slightly with increased velocity; however it remains the predominant Rotator Cuff muscle active during the movement (SOURCE-3).
Along with Teres Major , Teres Minor , Long Head of Triceps and the Posterior Deltoid , the Infraspinatus is a prime mover for GH Joint - Adduction and GH Joint - Extension (SOURCE-21). The Infraspinatus and Teres Minor externally rotate the Humeral Head during these movements to afford adequate clearance of the Greater Tubercle of Humerus from the Acromion (SOURCE-21). During GH Joint - Internal Rotation , the Infrapinatus is eccentrically contracted.
The Infraspinatus also acts on the Scapula , with a contraction in anatomic position producing abduction of the Inferior Angle (SOURCE-22). When weight-bearing with a straight arm (such as a Push-Up position), the Infraspinatus externally rotates Humerus relative to fixed Scapula which affords proximal stabilisation for motions such as Elbow - Pronation produced by the Pronator Quadratus (SOURCE-21).
When compared to the Supraspinatus , Tears and degeneration rarely affect the Infraspinatus in isolation, which often subjects discussion of these pathologies to include “all other Rotator Cuff Muscle s”. Provided (i) the Infraspinatus tendon fuses with that of the Supraspinatus and shares continuity with the Subscapularis and Teres Minor all near their humeral attachment, (ii) 58-80% of isolated Supraspinatus tears that progress to other Rotator Cuff Muscles extend posteriorly onto the Infrapsinatus tendon and (iii) the presence of a Rotator Cuff Tear may alter the mechanical properties of the remaining intact cuff tendon s, clustering their degenerative courses is likely valid (SOURCE-22+23+29).
Degeneration of the Rotator Cuff tendons is considered an intrinsic Rotator Cuff Tendinopathy that is often the consequence of overuse, overload or age (SOURCE-28+30). A traditional model of Rotator Cuff degeneration initiates with acute tendinitis which progresses to tendinosis and eventually onto tear s; however, the lack of consistency with the presence of inflammatory cells challenges this notion (SOURCE-30). While Inflammation may play a transient or reactive role, the chronic pain and structural failure are primarily driven by degenerative processes independent of it. The more modern perspective on Rotator Cuff degeneration is consistent with other Tendinopathy , where excessive stress exceeds the healing capacity of the Tenocytes and causes the Tendon to repair improperly (SOURCE-31). Vulnerability is most prominent at theCritical Zonenear the Rotator Cuff ’s tendinous instertions on the Humerus as it is hypovascular, although the extent to which is debated (SOURCE-28). Tendon vascularity may also be determined by chronicity as acute tendinopathies displayed hypovascularity, while chronic tendinopathies were hypervascular near degenerative changes (SOURCE-28).
Intrinsic tendinopathies follow a similar disease progression where the tissue undergoes several structural alterations which compromise its integrity and consequent function (SOURCE-28+30):
Matrix - in a healthy healing process, Type-III Collagens are rapidly laid down in haphazard fashion as a temporary “patch-job” and eventually succeeded by more permanent and organised Type-I Collagens (SOURCE-32). Type-III fibres are thinner, weaker and more irregularly arranged, so when demand for repair exceeds the rate at which this healthy healing process can occur, these fibres are accumulated and the strength of the tendon is compromised (SOURCE-28+30). The articular side of Rotator Cuff tendons appears to be more affected than the bursal side, with more profound degenerative changes in the intermediate and deeper tendon layers (SOURCE-28+30). Rotator Cuff Tendinopathy is associated with greater apoptosis of its Tenocytes , which is reflected in a reduction of the total Collagen content and consequent tendon thickness (SOURCE-28). For Rotator Cuff Tendinopathy , tendon thickness may be associated with chronicity. In the acute phase, tendon thickening may be apparent due to the accumulation of Glycosaminoglycans , the disorganisation of Collagen and possibly increased turnover rates (SOURCE-28). Conversely, with chronicity the tendon is likely to thin for the aforementioned morphological reasons (SOURCE-28). Additionally, Amyloid deposits within the Rotator Cuff suggest irreversible structural damage (SOURCE-30)
Fibrocartilaginous Metaplasia - movement between individual subunits of degenerated tendon tissue and with the corresponding bone causes internal compressive forces, with chronic exposure stimulating Tenocytes to produce fibrocartilage rather than Collagen (SOURCE-30). While fibrocartilage is well-suited to resist compressive and shear forces, it is notably less resistant to tensile loads (SOURCE-30)
Vascular - both reduced and increased vascularisation may be implicated in the pathogensis and mechanism of Rotator Cuff Tendinopathy (SOURCE-28). Neovascularisation in regions of degenerative changes and smaller tendon tears are thought to be a part of the healing response to micro-trauma; however, the new vessel growth may infiltrate sites of damage and displace the collagen matrix, leading to further compromise (SOURCE-28+31). Conversely, deficient vascular supply may be detrimental to tendon health (SOURCE-28). Sites of decreased vascularity such as theCritical Zoneor more specifically to the Infraspiantus, theRotator Crescentcontained within this zone are the most common sites of injury and have diminished healing capacity (SOURCE-28). While it is unclear whether it is a cause of consequence, tendinopathies that progress to a complete tears are often avascular (SOURCE-28). The bidirectional relationship tendinopathies share with vascularity may be attributed to chronicity. Acute tendinopathy is described to be hypovascular, while hypervascularity near sites of degenerative changes is associated with chronic tendinopathy (SOURCE-28)
Fatty Infiltration - the infiltration of adipose tissue is indicative of tendinopathy chronicity and muscle atrophy. Fatty degeneration negatively impacts function but not pain (SOURCE-26). Fatty infiltration of both the superior and inferior partitions of the Infraspinatus resulted in weaker GH Joint - Abduction , while isolated infiltration of the inferior partition also correlated with weaker GH Joint - External Rotation (SOURCE-26)
As insinuated by the term “degeneration”, Rotator Cuff pathology is progressive, with >50% of individuals that were once asymptomatic developing pain and disability over a four year period (SOURCE-28). Ageing is considered a major risk factor for Rotator Cuff Tendinopathy as it leads to many undesireable changes in the tendon , including a reduction in overall Collagen content, a higher proportion of Type-III collagens, a decrease in Glycosaminoglycans and Proteoglycans and calcification/ fibrovascular proliferation even in absence of a history of shoulder injury (SOURCE-28+30).
Rotator Cuff Tears are described to be one of the most common pathologies to affect The Shoulder Girdle with an estimated prevalence of 22% in the general population (SOURCE-35+36). This number increases dramatically with age, with 70-80% of those over the age of 80 expected to develop tears, which signifies the bidirectional relationship between Rotator Cuff degeneration and tears (SOURCE-32+34+36). Degeneration accounts for the vast majority of Rotator Cuff Tear s, with both extrinsic and intrinsic factors compromising the cuff and predisposing progressive failure of its tendon (s) (SOURCE-33+37). With or without the accompaniment of acute injury, the degenerative cuff may follow a disease progression that eventually leads to a full-thickness Tear (SOURCE-33). While partial-thickness tear may heal in 10% of instances or become smaller in another 10%, over half will propagate with 28% becoming a full-thickness tear (SOURCE-33). The typical degenerative progression may be described in several stages as identified by the tear shape (SOURCE-29+33):
Initial Stage - anterior fibres of the Supraspinatus sustain a “peel-off” lesion on their articular side. Most often this occurs approximately 7-15mm behind the anterior attachment of the Supraspinatus on the Glenohumeral Joint Capsule , where the tendon is most thin. Functional compromise may be minimal as theRotator Cableand Anterior Supraspinatus tendon remain intact
Pinhole Tear - over a period of potentially months-to-years the “peel-off” extends to the bursal surface, forming a pinhole-type appearance within the anterior Supraspinatus . An associated inability to adequately centre the Head of Humerus predisposes chronic impingement and the related cascade which includes thickening of the Coracoacromial Ligament
Cresecent Tear - as the Supraspinatus tendon is stronger anteriorly, the tear usually (58-80%) propagates posteriorly to include the Infraspinatus tendon to form a crescent-like appearance. This may occur over an extended period of time unless compounded by acute trauma
U or L Shape Tear - the formation of contractures within the Glenohumeral Joint Capsule paired with continuted action of the attaching musculature progresses the tear to resemble a deep U or L shape. In this later stage, joint reaction forces are significantly impaired and the Head of Humerus migrates superiorly
“Bald-Head” Tear - continued contracture formation and muscle activity results in retraction. The Infraspinatus ruptures and subluxes in an inferior direction, leaving the Head of Humerus exposed to give it a “bald-head” appearance
The severity (size >1-1.5cm and retraction) of tear expedites the disease process and is highly correlated to the extent of muscle atrophy and fatty infiltration (SOURCE-26+33). Fatty degeneration negatively impacts function but not pain (SOURCE-26).
The less common acute/ traumatic tear, accounts for approximately 8% of all Rotator Cuff Tears (SOURCE-37). These injuries are often the result of high-energy mechanisms or associated with overuse in overhead activities and more likely to result in immediate full-thickness compromise (SOURCE-37). While akin to degenerative tear s, the Supraspinatus is most often implicated in traumatic injury, concomitant injury to the Infraspinatus occurs in roughly 35-50% of cases (SOURCE-37). Infraspinatus tears are reported in 39% of all traumatic Rotator Cuff Tears (SOURCE-37). A tear of the Infraspinatus and Teres Minor results in active GH Joint - External Rotation weakness and an increase in passive GH Joint - Internal Rotation (SOURCE-37).
Infraspinatus hypertonicity has the capacity to exacerbate its actions on both the Head of Humerus and the Scapula :
Humerus - the Infraspinatus limits end-range GH Joint - Internal Rotation and may restrict this motion if it is excessively tight (SOURCE-20). As both the Infraspinatus and Teres Minor resist excessive Posterior Glide on Humerus , hypertonicity may compromise the necessary posterior translation during motions such as GH Joint - Internal Rotation (SOURCE-3+20). Chronic loss of Internal Rotation, as described inGlenohhumeral Internal Rotation Deficit (GIRD), is considered the initial step in the pathophysiologic cascade that leads to Internal Impingement (SOURCE-24). In certain populations such as the overhead throwing athlete, this leads to fibrotic adaptations in the Posterior Band of the Inferior Glenohumeral Ligament and the Posteroinferior Glenohumeral Joint Capsule and a consequent posterosuperior migration of the Head of Humerus during overhead motions such as throwing (SOURCE-24+25). This migration forms the basis of excessive strain as the Greater Tuberosity and articular surface of the Rotator Cuff impinge against the Posterosuperior Glenoid Labrum when The Shoulder Girdle is in an Apprehension Test -like position (SOURCE-25). This mechanism most often compromises the Posterosuperior Glenoid Labrum and Rotator Cuff (typically at the myotendinous junction of the Anterior Infraspinatus ) (SOURCE-24)
Scapula - at rest, restriction in the posterior shoulder (which includes Infraspinatus) pulls the posterior border of the Scapula laterally, resulting in forward positioning of the Scapula (excess Scapulothoracic Joint - Protraction and Anterior Scapular Tilting ) (SOURCE-2). This posture limits the Scapulothoracic Joint - Retraction and Scapulothoracic Joint - Upward Rotation required during Scapulohumeral Rhythm . Additionally, restriction in the posterior shoulder limits Horizontal GH Joint - Adduction (SOURCE-2)
Through many of the aforementioned mechanisms, Infraspinatus insufficiency may lead to impairment of its functions as a prime mover and stabiliser. Compromise of the Infrapsinatus and Teres Minor results in active GH Joint - External Rotation weakness and/or an increase in passive GH Joint - Internal Rotation (SOURCE-37). As the Infraspinatus has an inferior and medial draw on the Head of Humerus , dysfunction may lead to superior migration of the Humerus through action of the unopposed Deltoid (SOURCE-4+22). This forms the avenue for a sequelae which limits shoulder movements (namely later-stage elevation) and predisposes Subacromial Impingement . If left unchecked, chronic joint imbalance may lead to bony erosion of the Superior Glenoid and/or Acromion (SOURCE-38). This erosion, known asRotator Cuff Arthropathy, is described to be the fate of approximately 4% of full-thickness Rotator Cuff Tears (SOURCE-38).
In terms of Fascia l connections, the Infraspinatus is included in the following:
Myofascial Chains - the Infraspinatus is described as one of the more proximal muscles in the Dorsal Arm Chain (SOURCE-1)
A restriction at any point along the line/ chain could result in Pain or dysfunction of the Infraspinatus.
The accumulation of myofascial trigger points or Inflammation within the Infraspinatus may result in Referred Pain . Pain is often perceived most notably over the anterolateral shoulder and diffuse as it extends down the anterolateral arm - consistent with the Median Nerve distribution. Pain may also radiate to the medial border of Scapula (SOURCE-9).
Infraspinatus dysfunction may be a predisposing factor to the following pathologies or vice versa:
Subacromial Impingement - Rotator Cuff pathology can notably reduce the Subacromial Space to predispose impingement (SOURCE-4+22+42). Additionally, insufficent action from the Rotator Cuff may cause abnormal arthokinematics at the Glenohumeral Joint or Scapulothoracic Joint which may result in secondary impingement. Chronic impingement predisposes further Rotator Cuff pathologies such as Tendinopathy and/or tear . Those with impingement displayed a decreased co-activation ration between the Subscapularis and Infraspinatus and the Supraspinatus and Infraspinatus during arm elevation 0-30º and >90º (SOURCE-28)
Adhesive Capsulitis - Rotator Cuff pathology is considered a major intrinsic predisposing factor for secondary Frozen Shoulder (SOURCE-39). In the initialInflammatory Stage, shoulder motion becomes restricted despite full Rotator Cuff strength (SOURCE-39+40). Often the primary function of the Infraspinatus ( GH Joint - External Rotation ) is the first range of motion to become restricted, occuring as early as theInflammatory Stage(SOURCE-40+41).
Glenohumeral Instability - shares a bidirectional relationship with Rotator Cuff pathology. Insufficiency of the cuff is associated with recurrence of unstable events (SOURCE-43). Conversely, instability may predispose Rotator Cuff injury as it disturbs its length-tension relationships, leading to excessive strain or overuse. Infraspinatus tears are often attributed to anterior Glenohumeral Dislocation (SOURCE-22).
Suprascapular Nerve Entrapment - Infraspinatus weakness/atrophy is indicative of nerve compression (SOURCE-22). When the Supraspinatus is also affected, compression is likely near the Scapular Notch (SOURCE-22). When the Infraspinatus is affected in isolation, compression is usually attributed to a ganglion cyst at the Spinoglenoid Notch (SOURCE-22). Nerve compression is also common with overhead athletes and SLAP Lesions (SOURCE-22).
The following observations may be visible with Infraspinatus dysfunction:
Resting Posture
Infraspinatus Atrophy - may indicate Suprascapular Nerve palsy or a large (>5cm) or chronic Rotator Cuff Tear (SOURCE-6+22)
Pain - usually local to the anterolateral shoulder and diffuse as it descends the anterolateral arm, consistent with Median Nerve distribution (SOURCE-9). Pain may also extend to the Medial Border of Scapula (SOURCE-9). Greater pain usually experienced with partial- tears when compared to full-thickness (SOURCE-11)
Movement
Scapulohumeral Rhythm - mid-to-late range may be compromised
Glenohumeral Internal Rotation Deficit (GIRD)- may indicate hyperonicity of the posterior cuff, which includes the Infraspinatus (SOURCE-3+20+24)
Pain - exacerbated by movements such as arm elevation. Progressive worsening of Pain may be indicative of tear propagation (SOURCE-33)
In terms of Range of Motion assessment, disturbance of the following ranges may be indicative of Infraspinatus pathology:
Painful Arc - between 60-120º of arm elevation without significant muscle weakness may indicate a partial thickness tear (SOURCE-11)
GH Joint - External Rotation weakness while in 90º GH Joint - Flexion - may be indicative of Rotator Cuff Tear s, in particular a tendinous rupture of the Infraspinatus (SOURCE-22)
GH Joint - Internal Rotation restriction/Glenohumeral Internal Rotation Deficit (GIRD)- may indicate Infraspinatus hypertonicity (SOURCE-3+20+24)
Active Range of Motion - when compared to a full-thickness tear , partial-thickness tears are more likely to result in stiffness and Pain (SOURCE-11)
Manual Muscle Testing of the Infraspinatus can be performed to evaluate relative strength prone against gravity or seated without gravity (SOURCE-20). This is the same test used to evaluate the relative strength of the Teres Minor and compensation from the Posterior Deltoid is common (SOURCE-20):
Prone - active resisted GH Joint - External Rotation in 90º GH Joint - Abduction and Elbow - Flexion
Seated - active resisted GH Joint - External Rotation with arm by side and 90º Elbow - Flexion
Several Shoulder - Special Tests can be used to evaluate the integrity of the Infraspinatus:
Infraspinatus Test - sensitivity 0.51, specificity 0.84
External Rotation Lag Sign - sensitivity 0.97-0.98, specificity 0.93-0.98
Spurling’s Test - for suspected Nerve Root involvement ( Radiculopathy )
The Infraspinatus can be identified and palpated by either:
Upper bundle - working distal of the spine of the Scapula
Lower Bundle - working superior of the inferior angle of the Scapula
The Infraspinatus should be the most proximal muscle palpable between the Lateral Border of the Scapula and the Humerus . Its proximal border is defined by fibres of the posterior Deltoid while its distal border by the Teres Minor .
Relevant neurological assessments for the Infraspinatus focus primarily on its motor and sensory innervation from C5 and C6 Nerve Roots (SOURCE-6):
Myotomes - active resisted
As imaging findings alone do not consistently correlate with a patients symptoms and findings are often identified in asymptomatic shoulders, they should be complimented by physical examination before reaching a diagnosis and establishing a treatment protocol (SOURCE-10).
Radiographs (X-Rays)- generally the first line of imaging, used to determine presence of Acromial morphology or other related abnormalities such as Subchondral Cysts or a “notch” on the Greater Tuberosity or ligamentous calcification which may predispose impingement (SOURCE-11). X-Rays are also a reliable measure of theAcromiohumeral Interval, which quantifies the extent of impingement through determining the shortest distances between the inferior cortex of the Acromion and the peak of the Humeral Head (SOURCE-12). A distance of 7-14mm is considered normal, ≤ 7mm indicative of a large Rotator Cuff Tear and a distance smaller than 6mm indicates a chronic and complete tear of the Infraspinatus (SOURCE-12). The following views may be relevant (SOURCE-11+12+13+14+15):
AP view in the Scapula plane - also known asGrashey view, provides a (~20%) higher detection rate when compared to a conventional AP for the following conditions:
Osteophytes on the Greater Tuberosity of the Humerus or under the Acromion
Outlet view - reveals morphology of the Acromion, including bony spurs as well as ligamentous calcification and other causes of impingement
Axillary view - evaluates for Os Acromiale and rules out Dislocation in cases of trauma
When X-Ray findings are unremarkable, CT Scans and MRI’s may be indicated (SOURCE-15).
Ultrasonography (Ultrasound)- an accessible imaging modality with dynamic, real-time capabilities for the evaluation of Rotator Cuff pathology and Subacromial Impingement via certain metrics (SOURCE-10+11+16):
Rotator Cuff Pathology
“focal heterogenous hypoechogenicity”, or a localised portion of the tendon that has a dark and abnormal appearance, indicates the presence of a Rotator Cuff Tear . This may result from accumulated fluid within the cuff surface or its substance. Linear appearing echogenicity within the substance with or without muscle atrophy may also suggest a tear . A complete non-echogenic (black) gap extending the thickness of the tendon indicates a full tear, while in partial tears attachment is still visible
a decrease in tendon thickness was associated with Subacromial Impingement which is indicative of degenerative changes associated with chronicity
Bursa - the thickening of associated bursa as seen in Subacromial Bursitis is indicative of Subacromial Impingement. Similarly, an increased width of the Subdeltoid Bursa may be indicative of impingement. This Inflammation is visualised as an increase in anechoic fluid within the bursa
Subacromial Space - like other imaging modailities, the Acromiohumeral Inverval may be established with Ultrasounds to quantify impingement. A side-to-side differential of <2.1mm was considered normal.
AStandard I (transverse plane) Viewtaken approximately 15mm lateral of the Long Head of Biceps may be used to evaluate the rotator cuff, although this distance is subject to anatomical variation (SOURCE-16). AStandard II (longitudinal plane) Viewmay be used to determine the Acromiohumeral Interval with the Humerus neutrally rotated (SOURCE-16). Other views that may be relevant include Standard Auxiliary Views I, II and III (SOURCE-16). A downfall of this imaging modality is that accuracy is clinician dependent (SOURCE-16).
Magnetic Resonance Imaging MRI- can be used to evaluate the integrity of the Rotator Cuff , the presence of concomitant injuries such as Subacromial Bursitis or SLAP Lesions or associated morphologies (SOURCE-10+11+17). The following findings may be indicative of Rotator Cuff pathology (SOURCE-11):
T1-weighted images - an increased signal without tendon discontinuity indicates a partial- tear . On T1 and proton-density images an increased signal and loss of anatomic definition suggests Tendinitis
T2-weighted images - a signal increase with intra-tendinous focal defect suggests partial- tear . Conversely, Tendinitis may have moderate or decreased signal
Computed Tomography (CT) Scan- akin to MR-arthrography, used most often for the evaluation of Cartilage or the Glenoid Labrum (SOURCE-10). Typically reserved as a complement to other imaging modalities for the assessment of bony changes or when MRI’s are contraindicated (SOURCE-10).
Treatment of Infraspinatus pathology may be applied directly to the tissue or indirectly through its associated Fascia l and nervous structures.
The following Stretching techniques can be used to restore length to the Infraspinatus or reduce compromising mechanics such as impingement:
Sleeper Stretch - greater emphasis on GH Joint - Internal Rotation
Dowel External Rotation Stretch - self-guided GH Joint - External Rotation stretch with overpressure
Genie Stretch - rudimentary horizontal adduction stretch
Sleeper Stretch MWM - internal rotation stretch combined with Humerus Mobilisation
Shoulder Dislocates - mobility exercise that emphasises the greatest circumduction range possible
Shoulder External Rotation Stretch - rudimentary active stretch with large GH Joint - External Rotation range and several variations
Bent Over Lat Stretch - Horizontal GH Joint - Adduction variant
The following Strength exercises can be used to restore and improve functionality of the Infraspinatus:Early Phase:
Standing Shoulder External Rotations - incorporates upright torso posture
Rotator Cuff Banded Rotations - light low range isotonic rotation exercises
Prone Shoulder External Rotations - adds gravity or light load to Apprehension Test position
Prone Horizontal Abduction - achieves 88±25% of Maximal Voluntary Isometric Contraction (SOURCE-18)
Mid-Phase:
Face Pulls - bilateral isotonic horizontal pull exercise that emphasises GH Joint - External Rotation
Overhead Press - isotonic vertical push exercise with large overhead range
DB Shoulder Press - unilaterally loaded overhead press variation
Bottoms-Up Kettlebell Walk - isometric push/ stability exercise with or without perturbation
Late-Phase:
Push Press - wholebody, explosive variation of the Overhead Press
Kneeling Landmine Press - wholebody, explosive vertical pressing exercise with large overhead range
DB Snatch - unilateral isotonic, explosive shoulder exercise with large overhead range
Split Stance Landmine Press - crossbody, standing variation of the Kneeling Landmine Press
DB Snatch to Step-Up - wholebody DB Snatch variation that emphasises diagonal functional patterns
The Infraspinatus can be treated directly or along the Fascial Lines / Myofascial Chains they belong to, particularly at sites where hypertonicity is identified:
Practitioner Guided- deep sustained pressure or glides are applied to the Infraspinous Fossa/ Infraspinatus . GH Joint - Internal Rotation may be added to elongate the fibres, particularly when pressure is directed medially. Transverse Frictions may also be applied at sites of adhesion
Self-Guided:
Ball Release - lying supine over a trigger ball placed under the posterior surface of the Scapula , targeting pressure between the Spine of Scapula and its Inferior Angle and towards its humeral insertion
Altered arthrokinematics at The Shoulder Girdle can hinder tone and functionality of the Infraspinatus or leave it vulnerable to mechanical injury. While treating the muscle directly may improve said arthrokinematics, so too can mobilisations which in turn may improve Infraspinatus dysfunction. Similarly, mobilisations of the Cervical Spine may be relevant when Radiculopathy is suspected.
Joint Play - passive accessory movements performed without active movement
Posterior Glide on Humerus - Infraspinatus resists excessive posterior glide
Cervical Spine - for instances of Radiculopathy a PACVP , PAUVP or TVP may be applied to relevant Cervical segment(s) in addition to the following techniques:
Mobilisation with Movement - mobilisations applied with active movement
Shoulder - MWM 6 - Hand Behind Back, GH Internal Rotation
Shoulder - MWM 7 - Hand Behind Back, GH Internal Rotation
Shoulder - MWM 8 - Internal or External Rotation
Sleeper Stretch MWM - self-guided Posterior Capsule release
AC Joint - MWM 1 - GH Flexion or Horizontal Adduction
Cervical Spine - for suspected Radiculopathy , the following techniques may be indicated:
SMWAM - Cervical mobilisations with arm movement
Neurodynamic SMWAM - Cervical mobilisations with neurodynamic arm movement
Cervical SNAGS - Cervical mobilisations with neck movement
NAGS - particularly useful for restriction or Pain associated with movement for C2-C7
Dry Needling for the Infraspinatus is often indicated, with “trigger-points” occurring more often in the lower bundle of fibres (SOURCE-19). The following highlights points of focus when needling the Infraspinatus (SOURCE-19):Starting Position:
Patient can either be seated or prone
Procedure:
Typically a 30-40mm needle is used
Needle is inserted at an oblique (>45º) angle to the skin towards its insertion (anterolateral)
The muscle can be needled anywhere along the Infraspinous Fossa
Precautions:
The Lungs - angle and direction of needle are to help mitigate risk
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