Flexion at the Glenohumeral Joint occurs as the Head of Humerus spins in the Glenoid Fossa of Scapula resulting in elevation of the arm in a forwards direction. In the healthy shoulder, about 120º of strict or “true” Flexion occurs at the Glenohumeral Joint while as a composite motion for The Shoulder Girdle , roughly 160-180º of forwards elevation should be avaliable (SOURCE-3).
together these bones form the following relevant joints:
Prime Movers
Pectoralis Major (clavicular fibres)
Anterior Deltoid
Secondary
Stabilisers
Glenohumeral Joint Capsule - particularly posteroinferior fibres
The natural slight anteriorly facing bias of both the Glenoid Fossa on the Scapula and Scapula on Thorax means “pure” flexion at Glenohumeral Joint directs the Humerus anteromedially at a right angle to the scapular plane (SOURCE-6). Pure flexion does not require any rolling or sliding of the convex Head of the Humerus on the concave Glenoid Fossa, purely spinning (SOURCE-2+3). This spinning action draws capsuloligamentous structures taut, in particular the Posterior Glenohumeral Joint Capsule , Inferior Glenohumeral Ligament and Coracohumeral Ligament (SOURCE-2). As only 120º of pure flexion is available to the Glenohumeral Joint , to reach maximal vertical arm elevation of 180º, the Humerus must also slightly abduct which requires GH Joint - External Rotation to clear the Humeral Head from under the Acromion (SOURCE-2+6). This also counters the subtle internal rotation bias created by tension in the Coracohumeral Ligament as the arm is flexed beyond 90º (SOURCE-2). Similarly, tension in the Posterior Glenohumeral Joint Capsule is thought to produce a slight anterior translation bias on the Humerus (SOURCE-2). This maximal movement also requires contributions from the other articulations, namely Scapulothoracic Joint - Upward Rotation , SC Joint - Elevation and Acromioclavicular Joint upwards rotation (SOURCE-3). The ratio of Humeral to Scapula movement favours the Humerus slightly more in Flexion when compared to arm elevation in other planes (~2.4:1) (SOURCE-10).
This movement is facilitated predominately by the Clavicular fibres of the Pectoralis Major , Anterior Deltoid and Coracobrachialis with smaller contributions from the Biceps Brachii (SOURCE-6). When Flexion is performed against resistance from an Extended position; however, Sternocostal fibres of the Pectoralis Major make considerable contributions (SOURCE-6). The Moment Arm for the Anterior Deltoid is larger in the sagittal plane, making it more suited to Flexion (SOURCE-9). Conversely, the moment arms for the Supraspinatus , Posterior Deltoid and Subscapularis are all reduced as arm elevation moves from GH Joint - Abduction to Flexion (SOURCE-9).
Recuitment of the Rotator Cuff muscles appears to be direction specific in an attempt to counterbalance the potential Humeral Head translation required for each shoulder motion. For Flexion, the associated anterior humeral translation is offset by greater activity of the Posterior Rotator Cuff , namely Supraspinatus and Infraspinatus (SOURCE-26). The activity of these muscles appeared proportional to the load they were exposed to (SOURCE-26).
If arm elevation (flexion) occurs in the plane of the Scapula the kinematics increasingly resemble those of GH Joint - Abduction (SOURCE-10). Movement in this plane helps mitigate the risk of impingement by facilitating a greater Range of Motion without the need for external rotation of the Humerus . The kinematics of the remainder of The Shoulder Girdle during Flexion is discussed as part of the Scapulohumeral Rhythm . (SOURCE-2+6)
There are several tissues and pathological states related to The Shoulder Girdle that may impact the amount of Flexion available to the Glenohumeral Joint .
Soft-tissue restriction through hypertonic or eventually Contracture d states is arguably the most intuitive form of Flexion compromise. Capsuloligamentous structures that are pulled taut during Flexion such as the Posterior Glenohumeral Joint Capsule or Inferior Glenohumeral Ligament limit available range when restricted (SOURCE-3). Similarly, with Adhesive Capsulitis where the entire joint capsule becomes fibrotic, severely impeding the mobility of the Axillary Pouch (inferior portion) needed to facilitate spinning of the Head of Humerus during Flexion (SOURCE-4+11).
As clearance of the Humerus from under the Acromion of Scapula is integral to the final stages of flexion/ arm elevation, maintaining adequate subacromial space (or acromiohumeral distance) is essential. With soft-tissue restriction included, there are numerous ways by which there may be a mechanical or pathological narrowing of the subacromial space which predisposes Subacromial Impingement and threatens full range Flexion:
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 lead to anterosuperior migration of the Head of Humerus which encroaches on the available space and impinges anterior structures such as the Long Head of Biceps Tendon on the anterior rim
Insufficiency - conversely Muscle weakness or compromise may also narrow the subacromial space. The Rotator Cuff , in particular the Subscapularis , Teres Major , Latissimus Dorsi and Pectoralis Major (albeit greater in Abduction) are major depressors of the Humeral head which serve to offset the significant superior bias of the Deltoid (SOURCE-9). Rotator Cuff Tear s, for example, lead to superior migration during arm elevation with the severity of the tear corresponding to the extent of translation (SOURCE-7)
Scapular Dyskinesis - in addition to inaccurate placement of the Glenoid Fossa, Scapular Dyskinesis may restrict Flexion through impingement mechanisms. Compared to other planes of elevation, Flexion requires greater Internal Rotation and Posterior Tilting of the Scapula as well as less Scapulothoracic Joint - Upward Rotation , particularly in the early stages of movement (SOURCE-10). A loss of Posterior Tilting is linked to impingment while excessive Internal Rotation has been associated with Scapular Winging (SOURCE-10). Similarly a reduction in Upwards Rotation, which is a common finding with Dyskinesis, fails to adequately lift the Acromion to clear space for the Humerus (SOURCE-13). The movement is also limited by tension in the Rhomboids , Levator Scapulae and Trapezoid Ligament which restrict contribution from the Scapula . It is generally regarded that Dyskinesis reduces the subacromial space (SOURCE-7).
Humeral Rotation - while particularly at lower ranges Flexion requires less rotation than other planes of arm elevation, a failure of the Humerus to adequately perform GH Joint - External Rotation will still hinder its ability to clear the Acromion (SOURCE-10). Interestingly, many of the same tissues that restrict External Rotation are the same internal rotation muscles that depress the Humeral Head (SOURCE-3). Confusing things further, the greatest subacromial spaces (acromiohumeral distances) were recorded during arm elevation when GH Joint - Internal Rotation was added (SOURCE-7). The smallest subacromial space was recorded at 90º Flexion with neutral rotation (SOURCE-7). This seemingly contradictory information is likely attributed to the biphasic nature of elevation: the GH Joint - Internal Rotation is a subtle arthrokinematic consequence of capsular tension within the 120º of pure flexion, whereas GH Joint - External Rotation is a mandatory kinematic requirement for clearing the Greater Tubercle once the arm moves towards 180º of vertical elevation
Osseous Morphologies - the 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-25)
An “Impingement Zone” around 90º of Humeral elevation has been described as common compromising position (SOURCE-7).
A lack of Flexion at the Glenohumeral Joint may be compensated for through Thoracic - Extension , GH Joint - Abduction and Scapulothoracic Joint - Upward Rotation (SOURCE-3+14). Several shoulder pathologies including Subacromial Impingement and Adhesive Capsulitis have displayed either (i) a hypertonic response of the Upper Trapezius , which is believed to be compensatory or (ii) an increase of Scapulothoracic Joint - Upward Rotation (SOURCE-13+14).
Flexion of the Glenohumeral Joint may be limited by Pain , mechanical block or protective apprehension caused by several pathologies that affect The Shoulder Girdle . Additionally Flexion may represent a position of vulnerability for traumatic injury or the source of repetitive compressive forces which predisposes multiple acute and chronic injuries.
Adhesive Capsulitis - from the freezing stage and beyond Flexion may become restricted in response to Contracture formation within the Glenohumeral Joint Capsule and progressive loss of the Axillary Pouch (SOURCE-4+5). The loss of Flexion represents global capsular restriction.
Subacromial Impingement - represents the consequence of the various pathomechanical issues (such as those described in this section) that narrow the subacromial space. During Flexion, the superior migration of the Humerus causes compression of the subacromial structures against the Acromion (SOURCE-8). This typically provokes symptoms within the classicPainful Arc, with 90º of Flexion often considered a primaryImpingement Zone(SOURCE-7). The resulting Pain or mechanical block limits the available range.
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-16+17+18). Soft-tissue Inflammation from either condition may share a similar impingement fate. The resulting narrowing of the subacromial space may limit Flexion through Pain or mechanical means.
Scapular Dyskinesis - disturbed Scapula motion and control can hinder flexion primarily through interrelated mechanisms. For one this leads to abnormal placement of the Glenoid Fossa, the surface upon which movement occurs. Secondly, multiple common forms of dyskinesis may fall subject to the impingement cascade which also restricts flexion.
Glenohumeral Instability - the direction of instability suggests the tissues and motions that may be affected. Anterior instability insinuates less static resistance to the superior and anterior shear forces of the Deltoid . Traumatic compromise of the Rotator Interval formed by the Superior Glenohumeral Ligament , Coracohumeral Ligament and Long Head of Biceps Tendon leads to functional instability where the Head of Humerus may migrate anterosuperiorly (SOURCE-15). This leaves the shoulder vulnerable during motions such as Flexion where Pain or apprehension may limit motion (SOURCE-15)
Aside from Flexion limited by Pain , apprehension or a mechanical block, the following signs may be observed with pathologies that affect Flexion (SOURCE-21+22):
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
Dysrhythmia - loss of fluid, smooth motion. Ensuring adequate Scapulothoracic Joint - Upward Rotation and Posterior Tilting
Sulcus Sign - indicates laxity in the Glenohumeral caspuloligamentous structures, suggesting Glenohumeral Instability
Posture
Forward Head Posture - even in those with no history of pathology alters muscle activity (increased Upper Trapezius , decreased Lower Trapezius and Serratus Anterior ) which may contribute to shoulder Pain in Flexion (SOURCE-23)
Thoracic Spine Kyphosis - may be present with a forward shoulder posture which restricts Thoracic - Extension and Posterior Tilting for overhead Flexion
Flexion of the Glenohumeral Joint represents a major part of the Shoulder - Active Range of Motion and Shoulder - Passive Range of Motion assessment. Approximately 160-180º of active Flexion should be available to The Shoulder Girdle ; however, studies on the general population report ~160º as average (SOURCE-3+20). Of this composite motion, true Flexion at the Glenohumeral Joint is approximately 120º. Flexion appears to diminish with age and is often asymmetrical where the non-dominant side is slightly more restricted (SOURCE-20). During assessment the arm should be maintained straight to avoid restriction in the biarticular Triceps Brachii from hindering results (SOURCE-3). Flexion is often assessed in isolation at the Glenohumeral Joint and as a composite movement with motion from the Scapula (SOURCE-3+10+19):
Isolated Flexion - motion at the Scapula can be restricted to limit investigation to the Glenohumeral joint. To achieve this the patient may lie supine to fix their Scapula against the table and/or have the practitioner fix the Scapula in position
Composite Forward Elevation - inspect contributing motion of the Scapula for any signs of Scapular Dyskinesis such as Medial Border promience. For Flexion an approimate ratio of Humerus to Scapula motion is 2.4:1
If passive flexion is greater than flexion the patient can peform actively, neuromusculature is implicated. Isometric Tests of Flexion may also be revealing of contractile dysfunction. 90º of active Flexion is often described as theImpingement Zoneas it is often provocative of symptoms (SOURCE-7).
The following Shoulder - Special Tests may be relevant in the assessment of dysfunctional Flexion:Muscular:
Empty Can - assesses Supraspinatus
Lift-Off Test - assesses Subscapularis
Belly Press Test - assesses Subscapularis
Neers - compresses the subacromial structures through full Flexion
Hawkins-Kennedy - assesses impingement of the Rotator Cuff in 90º Flexion and GH Joint - Internal Rotation
Lateral Scapular Slide Test - measures distance between Scapula and Spine at various degress of elevation
Apprehension Test - with significant instability, even Flexion 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 C5 and C6 Nerve Roots most relevant to Flexion: Cervical - Myotomes (active resisted)
GH Joint - Abduction in Scapular Plane - could also perform in Flexion
Cervical - Dermatomes - evaluates sensory region
Together the C5 and C6 sensory distribution innervates the area of skin over the lateral arm from Deltoid to Thumb
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 Flexion 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-7).
Radiography (X-Ray)- evaluates Bone pathology which could mechanically block Flexion. 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-13+24). MRIs are also the preferred technique for evaluating soft tissues such as the Rotator Cuff , Subacromial Bursa and associated morphologies (SOURCE-24). 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-24). For Subacromial Impingement the following view are recommended (SOURCE-24):
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 Flexion 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.
The following Stretching techniques may directly or indirectly reduce Flexion restriction:
Forward Elevation Stretch - rudimentary passive stretch with moderate GH Joint - Flexion range
Genie Stretch - rudimentary horizontal adduction (Posterior Glenohumeral Joint Capsule ) stretch
Sleeper Stretch - Posterior Glenohumeral Joint Capsule stretch with greater emphasis on GH Joint - Internal Rotation
Bent Over Lat Stretch - accessible active stretch with large GH Joint - Flexion or Horizontal GH Joint - Adduction range
Dowel External Rotation Stretch - self-guided GH Joint - External Rotation stretch with overpressure
Door Frame Neck Stretch - Levator Scapulae variant
Seated Thoracic Rotation with Breathing - large lateral flexion and rotation range coupled with breathing
Shoulder Dislocates - mobility exercise that emphasises the greatest circumduction range possible
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 Flexion dysfunction, the following lists Flexion-based Strength exercises in rough descending order from most rudimentary:
Active or Active Assisted Flexion - weaker patients may benefit initially from the supine position as it lessens the effect of gravity and affords greater Scapula stability
Front Raises - isotonic GH Joint - Flexion exercise with many variations
Bottoms-Up Kettlebell Walk - isometric push/ stability exercise with or without perturbation
Lat Pulldown - eccentrically loads flexion, rudimentary weighted isotonic vertical pull movement with a high range of motion
Straight Arm Lat Pulldown - eccentrically loads Flexion, isotonic motion that emphasises Lats and straight arm strength
DB Pullover - eccentrically loads Flexion, moderate isotonic movement with large overhead and Thoracic - Extension range
Pull-Up - eccentrically loads flexion, bodyweight or greater load through large overhead motion
Overhead Press - isotonic vertical push exercise with large overhead range
DB Shoulder Press - unilaterally loaded overhead press variation
Kneeling Landmine Press - wholebody, explosive vertical pressing exercise with large
Split Stance Landmine Press - crossbody, standing variation of the Kneeling Landmine Press
DB Snatch - unilateral isotonic, explosive shoulder exercise with large overhead range
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 Flexion: Joint Play
Posterior Glide on Humerus - stretches Posterior Glenohumeral Joint Capsule which may restrict Flexion
Lateral Distraction on Humerus - particularly with the arm in 90º Flexion (SOURCE-1)
Scapulothoracic Rotation Glide - during Flexion the Inferior Angle of Scapula moves laterally (SOURCE-3)
Sternoclavicular Inferior Glide - the medial end of the Clavicle inferiorly glides during Flexion (SOURCE-3)
Acromioclavicular Inferior Glide - used for Pain through Flexion range or stiffness at end-range (SOURCE-1)
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-21):
Mobilisation with Movement - as Flexion is affected, mobilisations may benefit from the addition of movement:
Shoulder - MWM Techniques - Flexion 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 Flexion 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
AC Joint - MWM 1 - GH Horizontal Flexion
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-21)
Reverse NAGS - particularly useful for pain or restriction associated with movement of the Upper Thoracic region
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