Abduction of the Glenohumeral Joint occurs as the Head of Humerus upwardly rotates in the frontal plane about an anterior-to-posterior axis on the Glenoid Fossa of Scapula (SOURCE-11). In layman’s terms, Abduction describes raising your arm overhead in a lateral direction. In the healthy shoulder, roughly 120º of Abduction occurs at the Glenohumeral Joint. The remaining 60º required to perform the full 180º available to The Shoulder Girdle is achieved through Scapulothoracic Joint - Upward Rotation . This coupling of motion at both joints is known as the Scapulohumeral Rhythm . Abduction is therefore an integral motion available to The Shoulder Girdle .
together these bones form the following relevant joints:
Long Head of Biceps (if humeral head is laterally rotated)
As the Humerus Abducts away from the body the convex head of the Humerus rollssuperiorly (directed by the Supraspinatus ) andslidesinferiorly, remaining in close proximity to the Glenoid Fossa’s perpendicular (vertical) diameter (SOURCE-11). With the almost two-fold size disparity between the larger Humeral Head and longitudinal diameter of the Glenoid Fossa of Scapula ,roll-and-slidemechanics allow maximum motion without running out of articular surface (SOURCE-11). Compared to other directions of total arm elevation, Abduction requires slightly more contributions from the Scapula with a movement ratio of ~2.1:1 (Humerus:Scapula) and slightly more GH Joint - External Rotation to adequately clear the Head of Humerus from under the Acromion during the later stages of composite motion (SOURCE-18).
It is often reported that in the healthy shoulder the Supraspinatus facilitates the initial 15º of Abduction, after which it assists the Deltoid until roughly 90º of Abduction (SOURCE-11). One supporting factor for this is that the Moment Arms of the Anterior and Middle fibres of the Deltoid are smaller than those of the Supraspinatus , Infraspinatus and Subscapularis at low Abduction angles (0-40°). However by 60° these Moment Arms have more than doubled which is reflected in a peak activity of the Anterior + Middle fibres occurring between 60º-90º (SOURCE-13). The Moment Arm of the Anterior Fibres is further influenced by the extent of Humeral Rotation where added GH Joint - External Rotation can produce a favourable mechanical advantage even at 0º Abduction (SOURCE-13). Conversely, Abduction performed with GH Joint - Internal Rotation diminishes this advantage (SOURCE-13). Superior shear force bias of the Deltoid on the Humeral Head is offset by the depressor force couple of the Teres Major , Latissimus Dorsi and Pectoralis Major (SOURCE-17). While the majority of these joint depressors have a relatively consistent contribution across all planes of arm elevation, the Pectoralis Major is more suited to Abduction (SOURCE-17). With longer Moment Arms in arm elevation through Abduction the Supraspinatus , Subscapularis and Middle and Posterior Deltoid are most effective in this plane (SOURCE-17).The notion that the Supraspinatus initiates Abduction has been contended by recent literature which recorded near simultaneous pre-activity of both the Middle Deltoid and Supraspinatus prior to shoulder elevation, irrespective of load or plane (SOURCE-12). In either case, the contribution of these muscles are in close proximity and when one is impaired, the other may compensate (SOURCE-11+13). In terms of Torque , the following muscles contribute to Abduction (SOURCE-13):
Middle Deltoid ~ 35-65%
Subscapularis ~ 30%
Supraspinatus ~ 25%
Infraspinatus ~ 10%
Anterior Deltoid ~ 2%
Activation of these Glenohumeral Abductors also occurred in tandem with the axioscapular muscles contributing to Scapulothoracic Joint - Upward Rotation (SOURCE-12).
The Supraspinatus Tendon often blends with the Glenohumeral Joint Capsule and neighbouring Coracohumeral Ligament and Superior Glenohumeral Ligament which affords the capsule additional dynamic stability when the muscle contracts (SOURCE-11). On the distal end of the Glenohumeral Joint , the inferiorslidingof the Humeral Head pulls the Inferior Glenohumeral Ligament taut. The ligament acts as a hammock to afford additional stability as it approaches end-range (SOURCE-11).
While Frontal Plane abduction is often used in evaluation, Scapula Plane Abduction, also known asscaptionis a more natural/ functional movement. The Scapula Plane is roughly 35º anterior to the Frontal Plane. Movement in this plane helps avoid impingement and facilitates more Range of Motion as there is greater subacromial clearance, reducing the extent of GH Joint - External Rotation needed (SOURCE-18). In the frontal plane, the relatively greater degree of Scapulothoracic Joint - Retraction leads to higher recruitment of all Trapezius fibres. Comparatively, Abduction occurring in the Scapula Plane (greater Scapulothoracic Joint - Protraction ) recorded higher activity of the Upper Trapezius , Lateral Deltoid and Serratus Anterior (SOURCE-9). Similarly muscular activity was recorded during Abduction with increased Scapulothoracic Joint - Elevation which lead to greater contributions from the Lateral Deltoid and Upper Trapezius (SOURCE-9).
Abnormal Glenohumeral Abduction is typically attributed to insufficient or absentinferior glidemechanics of the Humeral Head, which results in impingement of Supraspinatus muscle and/ or tendon and the Subacromial Bursa , resulting in a pathology known as Subacromial Impingement (SOURCE-11). TheImpingement Zoneat 90º of arm elevation is a position where impingement frequently occurs (SOURCE-16). There are several mechanisms by which impingement can occur during Abduction that are typically associated with:
Soft-Tissue Restriction - while there are many soft-tissues that, when restricted, may lead to impingement and indirectly limit the later stages of Flexion, the Posterior Glenohumeral Joint Capsule is one such tissue that directly affects the joint. When shortened this may restrict the slight posterior glide of the Head of Humerus necessary during Abduction which encroaches on the available space and predisposes impingement. An indicator of restriction in the Glenohumeral Joint Capsule is excessive Scapulothoracic Joint - Upward Rotation in the early phases of Abduction as it may represent a compensatory mechanism (SOURCE-2). Although the end-range of maximal arm elevation in any plane is comparable, the Humerus typically has greater GH Joint - External Rotation throughout Abduction which is necessary for the Humeral Head to clear from under the Acromion during the later stages of elevation (SOURCE-18). While the Subscapularis is a major depressor of the joint, as a GH Joint - Internal Rotation muscle it also limits External Rotation. Restriction in this muscle may limit the External Rotation required for adequate clearance of the Acromion and also predispose impingement.
Muscle insufficiency - pre-fatigue of the Rotator Cuff has displayed a significant impedance on acute Abduction strength (average reduction of 54%) and narrowing of the Subacromial Space (2-14mm or 6-40%) through superior migration of the Humeral Head (SOURCE-10). This has been attributed to a reduced ability of the Rotator Cuff to counter the superior bias of the Deltoid , which disturbs Glenohumeral arthrokinematics and the length-tension relationship of associated musculature. In a similar fashion, Rotator Cuff Tears may lead to superior migration of the Humeral Head, with the severity of tear correlated with the extent of migration (SOURCE-16). It has been reported without the action of the Serratus Anterior , Scapulothoracic Joint - Upward Rotation is significantly restricted and arm elevation fails to exceed 90º (SOURCE-3)
Scapular Dyskinesis - in addition to inaccurate placement of the Glenoid Fossa, altered Scapula mechanics have been shown to narrow the subacromial space to restrict Abduction through impingement (SOURCE-16). Compared to other planes of elevation, Abduction requires greater Scapulothoracic Joint - Upward Rotation , particularly in its initial stages (SOURCE-18). This Scapula motion is often restricted in those with Dyskinesis where it fails to adequately lift the Acromion to clear space for the Humerus , leading to impingement (SOURCE-8)
Osseous Morphologies - anatomical variations such as a Hooked Acromion or degenerative formation of Osteophytes (or bone spurs) on the underside of the Acomion may abrade the local soft-tissues during arm elevation often restricting it by Pain (SOURCE-20)
Independent of the impingement cascade, these factors and others may comprise Abduction through diverging mechanisms:
Restriction - as seen in its severe form with Adhesive Capsulitis , restriction in the Inferior Glenohumeral Ligament (IGHL), its Axillary Pouch and the corresponding Glenohumeral Joint Capsule may limit end-range Abduction (SOURCE-11). Tension in the IGHL increases incrementally with Abduction and GH Joint - External Rotation , particularly when performed in combination (SOURCE-22). This leaves the later stages of either motion subject to restriction from the IGHL. From a muscular perspective, the Latissimus Dorsi , Teres Major and Sternal Head of the Pectoralis Major all oppose Abduction and can therefore leave it restricted in a hypertonic state (SOURCE-17). Indirectly through attachment on the Scapula , tension in the Rhomboids , Levator Scapulae , Pectoralis Minor and Trapezoid Ligament all restrict contribution from the Scapula (SOURCE-11). Restriction of the Vertebral Column may also impair Abduction. Excessive Kyphosis of the Thoracic Spine markedly decreases the available Abduction range and Strength by restricting necessary Thoracic - Extension and Posterior Tilting required for full overhead motion (SOURCE-6+15)
Laxity - laxity of certain stabilisers may perturb appropriate arthrokinematics of the Glenohumeral Joint , leading to unchecked movement of the Head of Humerus and consequent limitations of movement due to Pain or apprehension of Subluxation / Glenohumeral Dislocation . Traumatic compromise of the Rotator Interval is one such example. The Interval formed by the Superior Glenohumeral Ligament , Coracohumeral Ligament and Long Head of Biceps Tendon leads to functional instability where the Humeral Head may migrate anterosuperiorly (SOURCE-21)
Forced External Rotation from a combined position of Abduction, GH Joint - External Rotation and GH Joint - Extension leaves the shoulder particularly vulnerable to Anterior Glenohumeral Dislocation (SOURCE-14)
Abduction of the arm may be limited by Pain , mechanical block or protective apprehension caused by several pathologies that affect The Shoulder Girdle . Additionally Abduction may represent a position of vulnerability for traumatic injury or the source of repetitive compressive forces which predisposes multiple acute and chronic injuries.
Subacromial Impingement - represents the consequence of the various pathomechanical issues (including those described in this section) that narrow the subacromial space. During arm elevation the Head of Humerus migrates superiorly which narrows the subacromial space, which typically provokes symptoms within thePainful Arc(~70-120º), with 90º of Abduction considered a primaryImpingement Zone(SOURCE-16+27+28). Abduction is typically the most dysfunctional shoulder motion in impingement, affected by either weakness and/or Pain (SOURCE-5+27).
Rotator Cuff - insufficiency from either a Rotator Cuff Tear or Rotator Cuff Tendinopathy can lead to an impingement cascade as the Rotator Cuff cannot effectively offset the superior and anterior shear force of the Deltoid (SOURCE-24+25+26). Soft-tissue Inflammation from either condition may share a similar impingement fate. The resulting narrowing of the subacromial space may limit Abduction through Pain or mechanical means.
Adhesive Capsulitis - one study found Abduction restriction to be ubiquitous with Capsulitis; however, it is also restricted in the majority of other painful shoulder conditions, making it sensitive but not specific (SOURCE-4). This may in part be due to stiffness in the Inferior Glenohumeral Ligament , which is pulled taut nearing end range (SOURCE-11). From the Freezing stage, this structure progressively forms Contractures and loses its Axillary Pouch, leading to a capsular pattern of restriction where Abduction is typically the second Range of Motion to be affected after GH Joint - External Rotation .
Scapular Dyskinesis - disturbed motion of the Scapula is often reciprocated at the Glenohumeral Joint . For Abduction, reduced movement at one joint if often compensated for by the other (SOURCE-8). Dyskinesis may lead to abnormal placement of the Glenoid Fossa, the surface upon which movement occurs. Additionally, multiple common forms of abnormal Scapular mechanics fall subject to the impingement to also limit Abduction.
Thoracic Spine Kyphosis - a slouched posture of the upper back results in a significant reduction in active Abduction (SOURCE-15)
Subacromial Bursitis - as the Inflammation causes these structures to be more easily compressed this condition may restrict Abduction.
Aside from Abduction limited by Pain , apprehension or a mechanical block, the following signs may be observed with pathologies that affect Abduction (SOURCE-2):
A Painful Arc during Abduction, as the name suggests, represents Pain ful segments of Scapulohumeral Rhythm resulting from compression or Inflammation of structures under the Acromion and Coracohumeral Ligament . If present, pain is typically seen at two stages of the movement (SOURCE-29):
Glenohumeral Painful Arc- occurs roughly between 45º and 120º and can be caused by many pathologies, including: Subacromial Bursitis , Rotator Cuff pathology or Scapular Dyskinesis
Acromioclavicular Painful Arc- occurs in the last 10 to 20º of Abduction and suggests pathology of the Acromioclavicular Joint
Scapular Dyskinesis - there are several observations that may be revealing for those with abnormal Scapula movement:
Scapular Winging - asymmetrical lateral distance from the Thoracic Spine and/or Medial Border prominence
Scapular Tilting - excessive elevation of Superior Border or prominent Inferior Angle, indicating excessive anterior tilting which restricts subacromial clearance during Abduction
Dysrhythmia - loss of fluid, smooth motion. Ensuring adequate Scapulothoracic Joint - Upward Rotation and Posterior Tilting
Abduction of the Glenohumeral Joint represents a major part of the Shoulder - Active Range of Motion and Shoulder - Passive Range of Motion assessment. Approximately 170-180º of total active Abduction should be available to The Shoulder Girdle ; however, studies on the general population have reported ~150º as the average (SOURCE-1+11+23+29). Of this composite motion, true Abduction at the Glenohumeral Joint accounts for ~90-120º (SOURCE-1+11). Abduction appears to diminish with age and is often asymmetrical where the non-dominant hand is slightly more restricted (SOURCE-23). Most often Abduction should be assessed both in isolation and as a composite of motion across The Shoulder Girdle :
Isolated Abduction - with one hand the practitioner fixes the movement of the Clavicle and Scapula by pressing down on the Acromion and performs the movement with the other. This is used to evaluate tightness of the Glenohumeral Joint Capsule and the presence of any Subacromial pathology. While 90-120º of isolated Glenohumeral Joint Abduction is considered normal, it has been postulated that anything over 105º requires laxity in the Inferior Glenohumeral Ligament (SOURCE-29)
Composite Arm Elevation in Frontal Plane - to evaluate motion across the entire shoulder girdle, Scapulohumeral Rhythm is performed. An approximate movement ratio of 2:1 Humerus : Scapula should be apparent, although this is non-linear and highly variable (SOURCE-29). While better described on its respective page, during Scapulohumeral Rhythm the Humerus is either the sole or predominant contributor to movement up to 90º arm elevation, beyond this point the two structures contribute in a comparable fashion (SOURCE-29). Assessment of this motion may reveal Pain or other forms of dysfunction that may suggest particular tissues or pathologies. If a Painful Arc is present, it may be useful to perform accessory motions ( Joint Play ) within the specific range of Pain (SOURCE-7). Findings should be compared to the asymptomatic side and consider the ascending and descending phases of the movement
If passive Abduction is greater than Abduction the patient can perform actively, neuromusculature is implicated. Isometric Tests of Abduction may also be revealing of contractile dysfunction. 90º of active arm elevation is often described as theImpingement Zoneas it is often provocative of symptoms (SOURCE-16).
Horizontal Abductiondescribes abduction (or extension) of the arm in a posterior direction from a position of 90º of Abduction. In the healthy shoulder, roughly 45º of movement should be available in this direction.
The following Shoulder - Special Tests may be relevant in the assessment of dysfunctional Abduction:Muscular:
Empty Can - assesses Supraspinatus
Full Can - assesses Supraspinatus
Lift-Off Test - assesses Subscapularis
Belly Press Test - assesses Subscapularis
Drop Arm Test - assesses Supraspinatus
Neers - compresses the subacromial structures through full Flexion
Hawkins-Kennedy - assesses impingement of the Rotator Cuff in 90º Flexion and GH Joint - Internal Rotation
Painful Arc - pain usually occurs between 70-120º Abduction
Lateral Scapular Slide Test - measures distance between Scapula and Spine at various degress of elevation
Apprehension Test - with significant instability, Abduction may be apprehensive
Load & Shift Test - evalautes the direction and degree of instability
Spurling’s Test - evaluates potential Radiculopathy from the Cervical Spine
The following tests may be conducted to rule in/out nerve contribution with the C5 Nerve Root most relevant to Abduction: Cervical - Myotomes (active resisted)
GH Joint - Abduction in Scapular Plane - C5 - C6
Scapulothoracic Joint - Protraction ( C5 - C7 ) - for Scapulothoracic contribution
Cervical - Dermatomes - evaluates sensory region
Reflex - diminished reflex indicates potential lesion at corresponding nerve root
Upper Limb Nerve Tension Tests
The following imaging modalities may be relevant for the evaluation of Abduction dysfunction:
Ultrasonography (Ultrasound)- a highly accessible imaging modaility with real-time capabilities for the evaluation of soft-tissues including the Subacromial Bursa , Rotator Cuff and their Tendons . A major limitation of this modaility is that it is highly operator dependent. Compared to other imaging modailities, Ultrasounds are less expensive/more practical in the evaluation ofAcromiohumeral Distance, a metric that determines the Subacromial Space (SOURCE-16).
Radiography (X-Ray)- evaluates Bone pathology which could mechanically block Abduction. In addition to visualisation of traumatic injuries such as Fractures to the Head of Humerus or Acromion of Scapula , X-Rays may reveal degenerative osseous changes such as Osteoarthritis , Sclerosis , Osteophytes (bone spurs) and joint space narrowing (Glenohumeral Joint or resting Acromiohumeral Distance).
Magnetic Resonance Imaging MRI- can be used to directly measure the acromiohumeral space with a reduction anticipated in impingement or measure associated metrics such as the width of the Subdeltoid Bursa which indicates impingement through the presence of Bursitis (SOURCE-8+31). MRIs are also the preferred technique for evaluating soft tissues such as the Rotator Cuff , Subacromial Bursa and associated morphologies (SOURCE-31). A “Halo-sign” around Long Head of Biceps Tendon may suggest severity as it represents Glenohumeral Joint effusion and synovial thickening may be visualised in chronic cases (SOURCE-31). For Subacromial Impingement the following view are recommended (SOURCE-31):
Proton-density and T1-weighted images in coronal plane
T2-weighed images in sagittal plane - high signal fluid within Bursa is a direct sign of Inflammation
MR-arthrography with contrast injection - capable of revealing more subtle findings like lesions of the Cartilage or Glenoid Labrum
The treatment of Abduction dysfunction should be specific to the underlying cause. For rehabilitation of common underlying conditions such as Subacromial Impingement , Rotator Cuff pathology, Scapular Dyskinesis or Adhesive Capsulitis , see their respective pages.
As detailed underPathomechanics, the main points of focus of Stretching for Abduction dysfunction are to restore length/ reduce tone in the Posterior Glenohumeral Joint Capsule , antagonist Muscles and/or address any global shoulder restrictions if present. The following lists stretching techniques that may be directly or indirectly relevant:Simple:
Passive Abduction - typically performed by the practitioner with the patient seated or supine
Shoulder External Rotation Stretch - rudimentary active stretch with large GH Joint - External Rotation range and several variations
Seated Thoracic Rotation with Breathing - large lateral flexion and rotation range coupled with breathing
Genie Stretch - rudimentary horizontal adduction stretch
Intermediate:
Door Frame Neck Stretch - self-guided neck stretch with several variations
Door Frame Shoulder Stretch - self-guided anterior shoulder stretch with large Horizontal GH Joint - Abduction range
Dowel External Rotation Stretch - self-guided GH Joint - External Rotation stretch with overpressure
Sleeper Stretch - greater emphasis on GH Joint - Internal Rotation
Bent Over Lat Stretch - accessible active stretch with large overhead or Horizontal GH Joint - Adduction range
Banded Capsule Rolls - split stance biceps variation that emphasises shoulder rotation
Advanced:
Shoulder Dislocates - mobility exercise that emphasises the greatest circumduction range possible
Swimmers Oblique Extensions - exercise that may be used to lengthen entire Lateral Line through large body-wide lateral-flexion range
Sleeper Stretch MWM - internal rotation stretch combined with Humerus Mobilisation
Wheel Pose - full bridge variation that lengthens entire anterior chain
Dead Hangs - whole body traction for Pull and Push muscles with large overhead range
As a specific training protocol relates to the underlying cause of Abduction dysfunction, the following lists Abduction-based Strength exercises or those that incorporate a component of Abduction in rough descending order from most rudimentary:
Active or Active Assisted Abduction - weaker patients may benefit initially from the supine position as it lessens the effect of gravity and affords greater Scapula stability
Rotator Cuff Pendulums - oscillatory motion that afford a distracting glide to the Humeral Head
Prone Cobra - isometric exercise that emphasises Middle and Lower Trapezius in Abduction
Band Pull-Apart - basic isotonic Horizontal Abduction exercise for Scapular Retractors
Side Raises - isotonic GH Joint - Abduction exercise with many variations
DB Back Fly - basic weighted Horizontal Abduction exercise
Overhead Press - isotonic vertical push exercise with large overhead range
Lat Pulldown - eccentrially loads arm elevation overhead, particularly relevant to Abduction with wide-grip
DB Shoulder Press - unilaterally loaded overhead press variation
Face Pulls - bilateral isotonic horizontal pull exercise that emphasises GH Joint - External Rotation and incorporates Horizontal Abduction
Chest Fly - large horizontal abduction range to emphasise lengthening of the Chest
Prone Lat Pulldown - Lat Pulldown variation that emphasises Thoracic - Extension
Lu Raises - large GH Joint - Abduction range with no Humerus rotation to promote Scapulothoracic Joint - Upward Rotation
Push Press - wholebody, explosive variation of the Overhead Press
DB Hang Clean - unilateral clean progression, often performed explosively that incorporates
Half DB Bench Press - unilateral isotonic horizontal pressing motion that emphasises the Anterior Sling
Pull-Up - bodyweight or greater load through large overhead motion
Kneeling Landmine Press - wholebody, explosive vertical pressing exercise with large overhead range
Split Stance Landmine Press - crossbody, standing variation of the Kneeling Landmine Press
DB Snatch - unilateral isotonic, explosive shoulder exercise with large overhead range
Medicine Ball Chest Press - plyometric horizontal pressing motion, often sports relevant
Rope Climb - pull-up variation with entire load bestowed on alternating arm
DB Snatch to Step-Up - wholebody DB Snatch variation that emphasises diagonal functional patterns
The following Mobilisation techniques may be relevant in the treatment of Abduction: Joint Play
Inferior Glide on Humerus - with arm in Abduction
Lateral Distraction on Humerus - advocated by Maitland as a treatment for limited Abduction, particularly when following a Humeral Neck Fracture (SOURCE-7)
Scapulothoracic Rotation Glide - during Abduction the Inferior Angle of Scapula rotates laterally (SOURCE-1)
Sternoclavicular Inferior Glide - during Abduction the medial end of the clavicle glides inferiorly (SOURCE-1)
Acromioclavicular Inferior Glide - advocated by Maitland for stiffness at end-range Abduction (SOURCE-7)
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:
Thoracic Spine - mobilisations of the upper segments may improve symptoms of shoulder dysfunction, where a rounded shoulder posture is present (SOURCE-30):
Mobilisation with Movement - as Abduction is affected, mobilisations may benefit from the addition of movement:
Shoulder - MWM Techniques - Abduction is a key component of many techniques, however, some may be more relevant than others to the CSIM . The following lists those movements that involve Abduction and other movements they’re paired with:
Shoulder - MWM 1 - Scapulothoracic Elevation, Gh Flexion, Scaption
Shoulder - MWM 2 - Scapulothoracic Elevation, Gh Flexion, Scaption
Shoulder - MWM 3 (mid-range) Gh Flexion
Shoulder - MWM 4 (mid-range) Gh Flexion, Scaption
Shoulder - MWM 5 (end-range) Gh Flexion, Scaption
Cervical Spine - in addition to NAGS or SNAGS applied to a relevant Cervical segment, the following techniques may be indicated with suspected Radiculopathy :
Thoracic Spine - mobilisations of the upper segments may improve symptoms of shoulder dysfunction, where a rounded shoulder posture is present (SOURCE-30)
Reverse NAGS - particularly useful for pain or restriction associated with movement of the Upper Thoracic region
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