The Subscapularis is the largest and most powerful of the four muscles that comprise the Rotator Cuff which collectively serve as the primary stabilisers of the Glenohumeral Joint and consequently, The Shoulder Girdle . The Subscapulais is the only Rotator Cuff muscle found on the anterior (ventral) surface of the Scapula (SOURCE-1).
The triangular-shaped Subscapularis is the largest of the Rotator Cuff muscle s, accounting for ~53% of the cuff’s muscle mass and the majoirty of the Scapula ’s anterior surface, from a site known as theSubscapularis Fossa(SOURCE-3+4+12+24+33). The Subscapularis has an extensive origin from the Subscapularis Fossa, which includes:
Periosteal Origin - approximately the medial two-thirds of the Subscapularis adhere to the Periosteum of the anterior surface of Scapula
Tendinous Intramuscular Septa - other fibres arise from several tendinous sheets that adhere to ridges on the Scapula
Superficial Fascia - the fascial layer that envelopes the Subscapularis and distinguishes it from Teres Major and Long Head of Triceps provides a large surface area for additional fibre origin
This extensive, often aponeurotic, origin leaves the Subscapularis interspersed with four to six tendinous bands (SOURCE-24+33). As fibres course laterally they converge near their Humeral attachment with the approximate superior two-thirds forming a broad tendon with a thick/round upper border that inserts onto the Lesser Tubercle of Humerus and the adjacent Anterior Glenohumeral Joint Capsule (SOURCE-4+12+24). This tendon insertion is wider superiorly as it tapers inferiorly and distinguished from the Neck of Scapula by large Subscapular Bursa (SOURCE-4+12). Conversely, the inferior-third of the Subscapularis attachment does not become tendinous and inserts as muscle fibres directly to Bone , on the distal Lesser Tuberosity and/or the anterior aspect of the Humeral Metaphysis (SOURCE-12+24).
The Supraspinatus tendon also gives off several tendinous expansions to neighbouring structures that reinforce the Anterior Glenohumeral Joint (as described inFunction). The superior Subscapularis interdigitates with the anterior Supraspinatus , helping define the boundaries of the Rotator Interval and tensioning its ligaments (SOURCE-24). Within the Rotator Interval , fibres of the Subscapularis blend with the medial Coracohumeral Ligament and Superior Glenohumeral Ligament to form a fibrous ring that hooks over the Long Head of Biceps to keep it centred within the Bicipital Groove (SOURCE-3+12+24). Furthering the interaction with the Glenohumeral Joint Capsule , ~2cm prior to the Subscapularis’ insertion onto the Lesser Tuberosity, the Tendon receives fibres from the neighbouring Middle Glenohumeral Ligament (SOURCE-2).
The superior and inferior portions of the Subscapularis receive their nervous innervation from the Upper Subscapular Nerve and Lower Subscapular Nerve , respectively. These arise from C5 , C6 Nerve Roots (SOURCE-1+4+12)
The Subscapularis is described to have a multicircumpennate Muscle Architecture characterised by a substantialPhysiological Cross-Sectional Area (PCSA)and significant muscle volume, particularly when compared to the other Rotator Cuff Muscles (SOURCE-8+10). This architectural configuration, allowing for a high density of contractile elements, prioritises robust force generation, which is crucial for its primary actions of internal rotation and dynamic stabilisation of the humeral head. While certain metrics are heavily contingent on the population evaluated and measurement methodology, the following has been reported:MRI of 10 subjects (5 female, 5 male) 24-37 years, 158-188cm tall and a bodyweight of 50-86kg (SOURCE-10):
PCSA - 14.1 ± 4.4 cm²
Total Muscle Volume - 164.5 ± 63.9 cm³
Total Muscle Length - 12.6 ± 1.4 cm
SOURCE-4 - variation is unusualOccasionally the proximal tendon extends additional fibres to the Bicipital Groove that are controversially referred to as the Transverse Humeral Ligament (SOURCE-1).
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-23). Like the Infraspinatus and Teres Minor , the Subscapularis 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, most critically in the first 0-60º (SOURCE-6+12+23).
Of the four Rotator Cuff muscle s, the Subscapularis is the largest and most powerful (SOURCE-1+7+24). The muscles primary role is GH Joint - Internal Rotation , for which it receives support from more superficial, non-cuff muscles such as the Anterior Deltoid , Pectoralis Major , Latissimus Dorsi and Teres Major (SOURCE-23). These muscles are considerably larger than their External Rotator counterparts, allowing the Internal Rotators to produce ~1.75x the isometric Torque (SOURCE-23). During GH Joint - Internal Rotation , contraction of the Subscapularis causes an anterior roll of the Humerus (SOURCE-23).
Depending on the position of the arm, the Subscapularis may also aid in GH Joint - Abduction , GH Joint - Adduction , GH Joint - Flexion and GH Joint - Extension (SOURCE-24). These distinct, often opposing functions, are attributed to its muscle architecture (SOURCE-1+7+12+24):
Superior Portion - this portion is more suited to arm elevation. Its mechanical advantage ( moment arm ) diminishes as the arm is raised between 0-60º GH Joint - Abduction , particularly with added GH Joint - Internal Rotation
Inferior Portion - this portion is more suited to stability through depression of the Head of Humerus , a role supported by the association of recurrent Anterior Glenohumeral Dislocation with Inferior Subscapularis attentuation and laxity. Unlike its superior counterpart, the moment arm of the distal fibres remains relatively constant throughout movement
In addition to dynamic stability of the Glenohumeral Joint , the Subscapularis also affords static stability to resist Anterior Glenohumeral Dislocation through its muscle bulk and its numerous tendinous extensions (SOURCE-24). The superior portion lends fibres to the Coracohumeral Ligament and Superior Glenohumeral Ligament to form the Biceps Pulley , which is responsible for supporting the proximal Long Head of Biceps Tendon on its course through the Bicipital Groove (SOURCE-4+12). Additionally, during overhead activity ( GH Joint - Abduction or GH Joint - Flexion ) the Subscapularis Tendon is bent around the undersurface of the Coracoid Process of Scapula , creating a pulley-like effect that exacerbates GH Joint - Internal Rotation force produced by the muscle (SOURCE-4). The superior Subscapularis which interdigitates with the anterior Supraspinatus helps define the boundaries of the Rotator Interval and tensions its ligaments to resist inferior and posterior displacement of the Humeral Head (SOURCE-24).
When compared to the Supraspinatus , Tears and degeneration rarely affect the Subscapularis in isolation, which often subjects discussion of these pathologies to include “all other Rotator Cuff Muscle s” (SOURCE-24). Provided (i) the superior Subscapularis tendon interdigitates with the anterior Supraspinatus , (ii) the majoirty (~85%) of full-thickness Supraspinatus tears also affected the Subscapularis in some capacity ( Tendinosis or tear ) and (iii) the presence of Rotator Cuff Tear may alter the mechanical properties of the remaining intact cuff tendon s, clustering their degenerative courses is likely valid (SOURCE-4+24+25+26).
Degeneration of the Rotator Cuff tendons is considered an intrinsic Rotator Cuff Tendinopathy that is often the consequence of overuse, overload or age (SOURCE-27+28). 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-28). 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-29). 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-27). Tendon vascularity may also be determined by chronicity as acute tendinopathies displayed hypovascularity, while chronic tendinopathies were hypervascular near degenerative changes (SOURCE-27).
Intrinsic tendinopathies follow a similar disease progression where the tissue undergoes several structural alterations which compromise its integrity and consequent function (SOURCE-27+28):
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-30). 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-27+28). Like other Rotator Cuff tendon s, the articular surface of the Subscapularis tendon appears to be more affected than the bursal side, with more profound degenerative changes in the intermediate and deeper tendon layers (SOURCE-24+27+28). 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-27). 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-27). Conversely, with chronicity the tendon is likely to thin for the aforementioned morphological reasons (SOURCE-27). Additionally, Amyloid deposits within the Rotator Cuff suggest irreversible structural damage (SOURCE-28)
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-28). While fibrocartilage is well-suited to resist compressive and shear forces, it is notably less resistant to tensile loads (SOURCE-28)
Vascular - both reduced and increased vascularisation may be implicated in the pathogensis and mechanism of Rotator Cuff Tendinopathy (SOURCE-27). 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-27+29). Conversely, deficient vascular supply may be detrimental to tendon health (SOURCE-27). Sites of decreased vascularity such as theCritical Zoneare the most common sites of injury and have diminished healing capacity (SOURCE-27). While it is unclear whether it is a cause of consequence, tendinopathies that progress to a complete tears are often avascular (SOURCE-27). 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-27)
Fatty Infiltration - the infiltration of adipose tissue is indicative of tendinopathy chronicity and muscle atrophy (SOURCE-24). For the Subscapularis, fatty infiltration typically affects the superior portion and may be graded on a scale of 0-4, where 0 indicates normal muscle and 4 suggests more than 50% of the muscle has been replaced by adipose tissue (SOURCE-24)
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-27). 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-27+28).
Unlike the other Rotator Cuff muscle s, the Subscapularis is subject to a unique set of anterior impingement mechanisms which lead to a familiar cascade of increased friction, compression and the accumulation of micro-trauma. For the Subscapularis, there are two primary mechanisms that embody Anterior Impingement:
Subcoracoid Impingement - theCoracohumeral Spaceis a small, narrow and osseous-ligamentous space located anterior of the Coracoacromial Ligament (SOURCE-31). Along with the Superior Glenohumeral Ligament and Middle Glenohumeral Ligament , the thickest part of the Subscapularis tendon resides within this space and like other forms of impingement, are left vulnerable when this space is reduced (SOURCE-31). This space may be encroached upon by several factors that are generally attributed to either an increase in volume of the contained tissues or a reduction in distance between the bony Lesser Tuberosity of Humerus and Coracoid Process of Scapula (SOURCE-24+31):The impinged tissues fall to a similar cascade to other forms of impingement, where the Subscapularis is exposed to increased tensile loads on its undersurface, consequent degeneration and further narrowing of the Subcoracoid Space (SOURCE-24).
Increased Volume - the bulking or swelling of soft-tissue that physically overcrowds the narrow space. This may be caused by the accumulation of acute Inflammation ( Subcoracoid Bursitis , Tendinopathy ), scar formation or calcification within the space. Additionally, overcrowding of the space may be caused by the physical displacement and tendinous retraction of a Subscapularis or Long Head of Biceps tendon tear or the “folding” of soft-tissues during particular motions (such as arm elevation with GH Joint - Internal Rotation )
Bony Reduction - a mechanical narrowing of the Subcoracoid Space may occur directly through bony abnormalities or indirectly through several soft-tissue pathologies that disturb the athrokinematics of the Glenohumeral Joint . Typically this involves large tears of the Infraspinatus and/or Subscapularis which leads to anteromedial displacement of the Head of Humerus . Aside from tissue “folding”, GH Joint - Flexion with GH Joint - Internal Rotation mechanically reduces the Subcoracoid Space
Biceps Pulley Failure - the Biceps Pulley is a composite ligamentous structure that stabilises the Proximal Long Head of Biceps Tendon on its course through the Bicipital Groove . It is formed by extentions from three neighbouring tissues, the Subscapularis Tendon , Superior Glenohumeral Ligament and Coracohumeral Ligament from anteromedially and the Supraspinatus Tendon from posterolaterally (SOURCE-32). Compromise of the Subscapularis fibres results in failure of the pulley, leading to Dislocation of the Long Head of Biceps Tendon (typically anteromedially) and consequent anteromedial displacement of the Head of Humerus (SOURCE-24+31+32). GH Joint - Flexion , GH Joint - Internal Rotation or a combination of these movements increase shear load on the pulley and form a common avenue for overuse (SOURCE-32). In the presence of anteromedial instability, these provocative movements may lead to impingement of the Subscapularis Tendon against the Anterior Glenoid Labrum / Rim (SOURCE-24). Disease progression folllows a familiar pathway of overuse to Tendinitis and/or Tendinosis , a partial- tear , dislocation of the Long Head of Biceps tendon from the Bicipital Groove and eventually complete tendon rupture (SOURCE-32). As the Long Head of Biceps Tendon is highly innervated, anterior pain in The Shoulder Girdle is likely experienced at every stage of this progression (SORUCE-31+32). A congenitally shallow Bicipital Groove or shorter Lesser Tuberosity of Humerus potentiates pathology of the Subscapularis and Long Head of Biceps (SOURCE-9).
Although Tears of the Subscapularis Tendon are most often attributed to degeneration and/or increased mechanical stress, traumatic injury may occur (SOURCE-34). Traumtic failure typically occurs when the Subscapularis is eccentrically loaded under maximal tension (SOURCE-24). Consequently, the Subscapularis is most vulnerable at maximal GH Joint - External Rotation and ~60º GH Joint - Abduction or forceful hyperextension (SORUCE_24).
Subscapularis Tendon Tears appear to fall on a sliding scale of severity from more common partial-thickness tears that preserve the majoirty of attachment and relation with other structures to less common full-thickness tears or Avulsion Fractures that may compromise the Biceps Pulley and positioning of the Head of Humerus (SOURCE-24+33+35). There are several classification systems for Subscapularis tendon tears (degenerative or traumatic) that have been established which are generally based on the size, location, involvement of related stuctures and signs of degeneration (SOURCE-24+33).
Low grade or partial- tears are usually limited to the upper quater-to-third of the Subscapularis Tendon , with superfical fibers intact while the deeper fibres that adhere to the Lesser Tuberosity are compromised (known asTensile Undersurface Failure (TUFF))(SOURCE-24+33). Moderate grade tears may extend the full-thickness of the Subscapularis’ tendinous insertion but spare it’s muscular attachments and the adjacent Inferior Glenohumeral Ligament (SOURCE-24+33). Full-thickness compromise of the superior portion is directly correlated with Biceps Pulley failure and anterior dislocation of the proximal Long Head of Biceps Tendon from the Bicipital Groove (SOURCE-35). High grade tears may involve complete detachment or Avulsion Fracture from the Lesser Tuberosity to compromise these previously spared structures and result in notable tendon retraction (SOURCE-24+33). In lieu of adequate anterior restraint, severe tears are likely to result in anterior subluxation of the Head of Humerus , disturbing arthrokinematics at the Glenohumeral Joint (SOURCE-33). Fatty infiltration is also included in some (Pfirrmann) classification systems as an indicator of degenerative chronicity (SOURCE-33).
Given the traumatic nature of these injuries, the often occur in younger patients (SOURCE_24).
The Subscapularis is pulled taut during GH Joint - External Rotation and may therefore limit the extent of its range of motion (SOURCE-22). As the sole anterior Rotator Cuff muscle , the Subscapularis plays an integral role Glenohumeral Joint stability in the anterior-to-posterior direction, particularly between 0-60º of GH Joint - Abduction (SOURCE-36). The Subscapularis is described as a muscle prone to tightness, which may be responsive or causative (SOURCE-36). A disturbed length-tension relationship in the Subscapularis may represent a guarded or protective response to insufficent action from the posterior cuff which fails to adequately centralise the Head of Humerus posteriorly (SOURCE-37). This is supported by counterintuitive findings in overhead throwers, where the primary soft-tissue deficit observed was GH Joint - External Rotation rather than GH Joint - Internal Rotation (SOURCE-37). Conversely, hypertonicity of the Subscapularis may be a contributing factor to Anterior Glenohumeral Instability as it excessively draws the Humeral Head anteromedially (SOURCE-36). While Subscapularis insufficiency is a recognised predisposing factor to Subacromial Impingement and Scapular Dyskinesis , so too is Subscapularis restriction through these disturbances to Glenohumeral Joint arthrokinematics (SOURCE-38+39).
As discussed throughout this section, insufficency by means of degeneration or tear bares notable physical consequences that includes altered arthrokinematics of the Glenohumeral Joint and the sequelae that follows. In absence of injury, Subscapularis insufficiency may fall to a similar, albeit less severe, cascade. Failure of the notably powerful Subscapularis to effectively depress and centre the Head of Humerus leaves the superior draw of the Deltoid less opposed. This functional deficit directly reduces the subacromial space during arm elevation, particularly the first 0-60º, leading to Subacromial Impingement (SOURCE-6+12+23). The Subscapularis also plays a stabilising role on the anteroposterior axis by forming theTransverse Force Couplealong with the opposing posterior cuff ( Infraspinatus and Teres Minor ). The coordinated balance between the anterior and posterior cuff may be disrupted by Subscapularis insufficiency, placing excessive load on the posterior cuff and related capsular structures. This may accelerate or predispose Rotator Cuff and/or capsulolabroligamentous pathology. The Subscapularis insufficiency which presents as weak GH Joint - Internal Rotation may predisposeGlenohumeral Internal Rotation Deficit (GIRD)and a sequelae that includes internal impingement (SOURCE-40).
In terms of Fascia l connections, the Subscapularis is included in the following:
Myofascial Chains - the Subscapularis 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 Subscapularis.
The accumulation of myofascial trigger points or Inflammation within the Subscapularis may result in Referred Pain . Pain is often perceived as a strong focal point on the posterior Glenohumeral Joint with a diffuse zone that extends from it. Pain may also radiate down the posterior upper arm or to the Carpals (SOURCE-11).
Subscapularis dysfunction may be a predisposing factor to the following pathologies or vice versa:
Subacromial Impingement - as the largest/ most powerful Rotator Cuff muscle and its only internal rotator, the Subscapularis is often left hypertonic due to an increased demand associated with impingement (SOURCE-12). With exception to the Supraspinatus , the Rotator Cuff affords an integral inferior bias to the Head of Humerus which counters the significant superior pull of the Deltoid . Insufficiency therefore forms the basis for secondary impingement. Through its extensive tendinous attachments and unique anterior location, Subscapularis compromise may also form an avenue for Anterior Impingement (described inPathomechanics).
Glenohumeral Instability - as the primary function of the Rotator Cuff is to appropriately centre the Head of Humerus in the Glenoid Fossa, insufficiency directly compromises the stability of the Glenohumeral Joint . With the thin an redundant nature of the anterior Glenohumeral Joint Capsule , the Humeral attachment of the Subscapularis is thought to be a major source of stability on the anteroposterior axis, where it opposes the posterior cuff ( Infraspinatus and Teres Minor ) (SOURCE-12). Supporting a bidirectional relationship, chronic instability events may compromise the Subscapularis and its functions (SOURCE-24). Those with recurrent Anterior Glenohumeral Dislocation displayed thinning, a loss of surface area and fibrosis/ scarring of the Subscapularis Tendon while muscle fibres displayed muscle fibre type modifications (SOURCE-24). Through traumatic means, Subscapularis injury often occurs concomitantly with other lesions such as Humeral Avulsion of the Glenohumeral Ligaments (HAGL) Lesions and Bankart Lesions (SOURCE-24).
Long Head of Biceps Pathology - as a notable anteromedial component of the Biceps Pulley , the Subscapularis is directly related to the Proximal Long Head of Biceps Tendon . Compromise of the superior Subscapularis fibres results in failure of the pulley, leading to Dislocation of the Long Head of Biceps Tendon (typically anteromedially) and consequent anteromedial displacement of the Head of Humerus (SOURCE-24+31+32). Sharing a bidirectional relationship, Biceps tendon Subluxations may result in partial or full-thickness tears of the Subscapularis (SOURCE-24).
Scapular Dyskinesis - either a predisposing factor or sequela of a Rotator Cuff Tear or Tendinopathy is altered positioning and Motor Control of the Scapula (SOURCE-41). Through direct action (or lack there of) of the Subscapularis or indirectly through its involvement in impingement both hyper and hypotonicity of the Subscapularis has the capacity to predispose dyskinesis of the Scapula . Compensation from other anterior stabilisers such as the Pectoralis Minor may lead to Anterior Scapular Tilting in the presence of Subscapularis insufficiency (SOURCE-39+42). Conversely, restriction may limit Posterior Tilting and External Rotation of the Scapula during arm elevation (SOURCE-43).
The following observations may be visible with Subscapularis dysfunction:
Resting Posture
Movement
Arm Elevation - Pain may be perceived during motion with Subscapularis dysfunction by means of impingement, most notably from 0-60º where its stabilising role is most prominent (SOURCE-24+36+43). An increase in Pain during arm elevation with GH Joint - Internal Rotation may be indicative of a Biceps Pulley Lesion and/or articular partial-thickness tear of the superior Subscapularis Tendon (SOURCE-24)
Scapular Dyskinesis - Subscapularis restriction may limit the neccessary posterior tilting and external rotation of the Scapula during arm elevation (SOURCE-43)
In terms of Range of Motion assessment, disturbance of the following ranges may be indicative of Subscapularis pathology:
Painful Arc - Pain during the first 0-60º of arm elevation may be indicative of Subscapularis dysfunction (SOURCE+24+36+42)
Weak GH Joint - External Rotation - a weak/ lengthened posterior cuff ( Infraspinatus and Teres Minor ) is often associated with Subscapularis restriction (SOURCE-43)
Scapulohumeral Rhythm - reduced GH Joint - External Rotation during elevation may indicate Subscapularis dysfunction
Increased Passive GH Joint - External Rotation - results from Subscapularis Tendon Tears (SOURCE-33)
Several Shoulder - Special Tests can be used to evaluate the integrity of the Subscapularis:
Bear Hug Test - sensitivity 0.52, specificity 0.85
Belly Press Test - sensitivity 0.75-0.80, specificity 0.88-0.97
Internal Rotation Lag Sign - sensitivity 0.41-0.97, specificity 0.91-0.96
Lift-Off Test - sensitivity 0.35, specificity 0.98
Manual Muscle Testing of the Subscapularis can be performed to evaluate relative strength prone against gravity or seated without gravity. Compensation from the Anterior Deltoid , Pectoralis Major , Latissimus Dorsi and Teres Major is common (SOURCE-22):
Prone - active resisted GH Joint - Internal Rotation in 90º GH Joint - Abduction and Elbow - Flexion
Seated - active resisted GH Joint - Internal Rotation in slight GH Joint - Abduction and 90º Elbow - Flexion
The Subscapularis can be palpated by drawing out the Scapula (laterally) to expose its internal surface (subscapular fossa) and then sinking fingers in its direction, following the contour of the Ribs . Confirmation can be made by instructing the patient to internally rotate or adduct.
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-13).
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-14). 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-15). 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-15). The following views may be relevant (SOURCE-14+15+16+17+18):
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-18).
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-13+14+19):
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-19). AStandard II (longitudinal plane) Viewmay be used to determine the Acromiohumeral Interval with the Humerus neutrally rotated (SOURCE-19). Other views that may be relevant include Standard Auxiliary Views I, II and III (SOURCE-19). A downfall of this imaging modality is that accuracy is clinician dependent (SOURCE-19).
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-13+14+20). The following findings may be indicative of Rotator Cuff pathology (SOURCE-14):
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-13). Typically reserved as a complement to other imaging modalities for the assessment of bony changes or when MRI’s are contraindicated (SOURCE-13).
Treatment of Subscapularis pathology my 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 Subscapularis or reduce compromising mechanics such as impingement:
Shoulder External Rotation Stretch - rudimentary active stretch with large GH Joint - External Rotation range and several variations
Dowel External Rotation Stretch - self-guided GH Joint - External Rotation stretch with overpressure
Door Frame Shoulder Stretch - self-guided anterior shoulder stretch with large Horizontal GH Joint - Abduction range
Split Stance Biceps Stretch ( Thumb up variant) - self-guided anterior shoulder stretch with large GH Joint - Extension range
Bretzel 1.0 - wholebody technical stretch that incorporates anterior shoulder
Bretzel 2.0 - variation with greater hip extension range
Wheel Pose - full bridge variation that lengthens entire anterior chain
Sleeper Stretch - greater emphasis on GH Joint - Internal Rotation
Sleeper Stretch MWM - internal rotation stretch combined with Humerus Mobilisation
The following Strength exercises can be used to restore and improve functionality of the Subscapularis:Early Phase:
Lift-Off Test - also makes for an effective early-phase isolation and activation exercise
Scaption > 120º with GH Joint - Internal Rotation - achieves 62±33% Maximum Voluntary Isometric Contraction (SOURCE-7)
Standing GH Joint - Extension from 90º to 0º
Behind Back GH Joint - Extension with GH Joint - Internal Rotation
Banded/ Cable
Barbell
Rotator Cuff Pendulums - oscillatory motion that afford a distracting glide to the Humeral Head
Shoulder Sling - Scapula setting exercise
Rotator Cuff Banded Rotations - light low range isotonic rotation exercises
Banded Horizontal Adduction - low load isotonic horizontal adduction exercise
Pallof Press - low load horizontal push exercise that emphasises anti-rotation of Core
Scapular Punches - isotonic exercise that emphasises Scapulothoracic Joint - Protraction
Banded Unilateral Lat Activations - activate lat, posteroinferior drawer on Humerus
Isometric Chest Squeezes - isometric exercise that isolates Chest
Chest Press Machine - rudimentary horizontal push machine
Mid-Phase:
Inverted Rows - rudimentary isotonic horizontal pull exercise that utilises bodyweight
Push-Up - bodyweight isotonic horizontal push exercise
Seated Row - rudimentary weighted isotonic horizontal pull movement
Lat Pulldown - rudimentary weighted isotonic vertical pull movement with a high range of motion
Overhead Press - isotonic vertical push exercise with large overhead range
One Arm Row - unilateral DB version of Seated Row
DB Shoulder Press - unilaterally loaded overhead press variation
Bench Press - isotonic horizontal push exercise with capacity for high loads
Incline DB Bench Press - unilaterally loaded Bench variation on variable incline
Chest Fly - large horizontal abduction range to emphasise lengthening of the Chest
Front Raises - isotonic GH Joint - Flexion exercise with many variations
Side Raises - isotonic GH Joint - Abduction exercise with many variations
Upright Row - weighted isotonic vertical pull exercise that emphasises Upper [[trapezius]
Farmers Carry - upperbody/ Core isometric exercise with perturbation of walking
Late Phase:
Bottoms-Up Kettlebell Walk - typically isometric exercise for entire arm musculature with perturbation from walking
DB Hang Clean - unilateral clean progression, often performed explosively
DB Snatch - unilateral isotonic, explosive shoulder exercise with large overhead range
Push Press - explosive overhead movement with large range that incorporates entire body
Kneeling Landmine Press - explosive Vertical Push exercise with a large overhead range
Split Stance Landmine Press - explosive unilateral, whole-body Vertical Push exercise
Medicine Ball Chest Press - plyometric horizontal pressing motion, often sports relevant
Suitcase Carry - unilateral farmers carry which emphasises crossbody functional patterns
DB Snatch to Step-Up - wholebody DB Snatch variation that emphasises diagonal functional patterns
Rope Climb - pull-up variation with entire load bestowed on alternating arm
The Subscapularis treated directly or along the Fascial Lines / Myofascial Chains it belongs to, particularly at sites where hypertonicity is identified:
Practitioner Guided- with patient typically lying supine (contralateral side-lying or seated may also suffice) the Scapula is passively drawn laterally from the Ribs to expose its anterior surface where the Subscapularis resides. The practitioners Fingers may follow the contour of the Ribs and press into the Subscapularis. To create a “pin and stretch” effect, pressure may be maintained while the patient is osciliated through shoulder rotation while the arm is in 90º Elbow - Flexion .
Self-Guided- using the end of a dowel or comparably shaped stick, the Subscapularis may be released in a similar fashion to how the Fingers are directed in the pracitioner guided technqiue described above. A towel may be added to the end of the dowel for a broader contact.
Altered arthrokinematics at The Shoulder Girdle can hinder tone and functionality of the Subscapularis 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 Subscapularis dysfunction. Similarly, mobilisations of the Cervical Spine may be relevant when Radiculopathy is suspected.
Joint Play - passive accessory movements performed without active movement
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 1 - applied to the Clavicle and Scapula
Shoulder - MWM 2 - applied to the medial Clavicle and Scapula
Shoulder - MWM 3 - applied to the Scapula and Humerus
Shoulder - MWM 4 - applied to the Scapula and Humerus
Shoulder - MWM 5 - applied to the Scapula and Humerus
Shoulder - MWM 6 - Hand Behind Back, GH Internal Rotation
Shoulder - MWM 7 - Hand Behind Back, GH Internal Rotation
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
The following lists key considerations when Dry Needling the Subscapularis (SOURCE-21):Starting Position:
Patient is typically prone with symptomatic Scapula pulled laterally away from the Thorax , their hand can rest overhead
Therapist sits perpendicular to patient Subscapularis
Procedure:
Using larger needles (~70mm)
With a flat grip needle is inserted at a shallow angle along the contour of the Ribs in an Anterior-to-Posterior direction
Deep just shy of Scapula , needle can also be inserted in a proximal to distal direction
Precaution:
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