Extension at the Glenohumeral Joint is defined as rotation or spinning of the Humerus in the Sagittal Plane about a Medial-Lateral Axis of rotation (SOURCE-2). In layman’s terms, Extension describes the movement of the arm directly behind them. The majority of Extension occurs at the Glenohumeral Joint with roughly 45-60º of active motion typically available (SOURCE-1+2+3+4). To reach further posteriorly The Shoulder Girdle compliments (or compensates) the Extension motion with motion at the Scapula and Thoracic Spine .
together these bones form the following relevant joints:
Prime Movers - contingent on arm position
Posterior Deltoid
Pectoralis Major (Sternocostal Fibres)
Stabilisers
Akin to GH Joint - Flexion , if movement occurs strictly in the sagittal plane, the Head of Humerus spins posteriorly on the face of the Glenoid Fossa of Scapula about a medial-lateral axis without the need for translation (SOURCE-2+3). Depending on the degree of Extension, this Humeral spinning pulls many of the joint’s capsuloligamentous structures taut to varying extents, including the Anterior Glenohumeral Joint Capsule , Glenohumeral Capsular Ligaments , Coracohumeral Ligament , Clavicular Fibres of the Pectoralis Major and the Long Head of Biceps Tendon (SOURCE-2+3+4). Most notably, tension in the Anterior Glenohumeral Joint Capsule pulls the Scapula into an anterior tilt as full Extension which serves as a compensatory pattern to increase the available range (SOURCE-2). In contrast, to achieve “true” or greater Extension of the Humerus relative to the Scapula , slight posterior tilting is required.
Muscular contribution is contingent on the position of the arm. With arm straight extension occurs behind the torso which is facilitated by the Posterior Deltoid , Teres Major and Latissimus Dorsi (SOURCE-1). If resisted extension occurs from any point of GH Joint - Flexion , Sternocostal fibres of the Pectoralis Major will also make contributions until the arm reaches the frontal plane (SOURCE-1).
Recruitment 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 Extension, the associated posterior humeral translation is offset by greater activity of the Anterior Rotator Cuff , namely Subscapularis (SOURCE-7). The activity of these muscles appeared proportional to the load they were exposed to (SOURCE-7).
Compromise of the anterior static structures usually pulled taut during Extension leaves the region vulnerable to Anterior Glenohumeral Instability , which may lead to a limitation of movement by Pain or apprehension. The Long Head of Biceps Tendon is pulled taut during Extension and described as a highly sensitive pain generating tissue and a notable source of pain for The Shoulder Girdle (SOURCE-8+9). This muscle and other soft-tissues may also limit Extension through simple mechanical restriction. Restriction of the anterosuperior to anteroinferior Glenohumeral Joint Capsule limits the necessary posterior spin and traces of anterior translation of the Head of Humerus (SOURCE-4). Although not the predominant movement affected, global restriction of the joint as in Adhesive Capsulitis is expected to restrict Extension, initially by pain and then through fibrosis.
There are multiple avenues by which insufficient Extension may be compensated for, including (SOURCE-3+4):
Anterior Scapular Tilting
Ipsilateral Thoracic - Rotation
In terms of trauma, forced External Rotation from a combined position of GH Joint - Abduction , GH Joint - External Rotation and Extension leaves the shoulder particularly vulnerable to Anterior Glenohumeral Dislocation (SOURCE-1).
Extension of the arm may be limited by Pain , mechanical block or protective apprehension caused by several pathologies that affect The Shoulder Girdle . Additionally Extension may represent a position of vulnerability for traumatic injury or the source of repetitive compressive forces which predisposes multiple acute and chronic injuries.
Anterior Glenohumeral Instability - compromise of the anterior static structures usually pulled taut during Extension leaves the region vulnerable to Anterior Instability, which may limit the movement through Pain or apprehension. Anterior dislocation often occurs from trauma involved with combined GH Joint - External Rotation , GH Joint - Abduction and GH Joint - Extension (SOURCE-1).
Scapular Dyskinesis - abnormal Scapula movement shares a polarising relationship with Extension of the Glenohumeral Joint . On one end of the spectrum, excessive Scapulothoracic Joint - Protraction or Anterior Scapular Tilting may limit available Extension range by bestowing further tension on the Anterior Glenohumeral Joint Capsule . On the other, aberrant motions such as Scapulothoracic Joint - Retraction may represent necessary compensation for insufficient Extension.
Long Head of Biceps Tendon - approaching end range Extension stretches the LHBT and the Rotator Interval it belongs to. These tissues are highly innervated for the region, making them a notable source of Pain for The Shoulder Girdle when provoked by means of trauma or repetitive strain (SOURCE-8+9). Additionally, compromise of these structures may succumb to the anterior instability cascade.
Adhesive Capsulitis - from the freezing stage and beyond Extension may become restricted in response to Contracture formation within the Glenohumeral Joint Capsule and progressive loss of the Axillary Pouch (SOURCE-10+11). The loss of Extension represents global capsular restriction.
Rotator Cuff Pathology - a primary role of the Cuff is maintain quality articulation between the Head of Humerus and the Glenoid Fossa of Scapula , which when impaired may lead to excessive Humeral movement or abnormal stress on local tissues. For Extension specifically, the Anterior Cuff ( Subscapularis ) is thought to play a notable role in offsetting the posterior translation bias of larger Extension muscles such as the Posterior Deltoid , Latissimus Dorsi and Teres Major (SOURCE-7). Failure to offset this bias has the potential to lead to acute or chronic Posterior Glenohumeral Instability and the sequelae that follows.
Aside from Extension limited by Pain , apprehension or a mechanical block, the following signs may be observed with pathologies that affect Extension (SOURCE-3+4+12+13):
Swallow Tail Sign- both arms do not extend to the same degree, usually suggesting Posterior Deltoid or Axillary Nerve injury
Long Head of Biceps Tendon - signs of compromise to the LHBT or the Glenoid Labrum it attaches to include:
Pain - most commonly associated complaint with SLAP Lesion s, typically felt anteriorly or on palpation of the Bicipital Groove
Mechanical Symptoms - Glenohumeral Instability and sensations of catching, popping or clicking associated with shoulder movement, in particular rotation. This often results in impaired throwing/ overhead capacity
Scapular Dyskinesis - signs of dyskinesis often associated with Extension include:
Excessive Anterior Scapular Tilting - a common compensatory response often observable with a prominent Inferior Angle of Scapula or an elevated Superior Border
Excessive Scapulothoracic Joint - Retraction - as indicated by medial border prominence
Extension of the Glenohumeral Joint represents a component of the Shoulder - Active Range of Motion and Shoulder - Passive Range of Motion assessment. Approximately 45-60º of “true” Extension is available to the Glenohumeral Joint with slightly more motion acheived through Anterior Scapular Tilting , Scapulothoracic Joint - Retraction , Thoracic - Flexion and ipsilateral Thoracic - Rotation (SOURCE-2+3+4). Unlike many shoulder motions, both active and passive Extension appears to be slightly greater on the non-dominant side (SOURCE-6). Extension range of motion also diminishes with age (SOURCE-6).To isolate Extension to the Glenohumeral Joint , have the patient lying prone and stabilise their Scapula by placing one hand over the bone to resist excessive anterior tilting. The Humerus can then be actively or passively moved into the available Extension. For passive assessment, slight Elbow - Flexion is maintained to prevent hypertonicity in the biarticular Biceps Brachii from interfering with findings (SOURCE-3). The end-feel is described as a firm tissue stretch (SOURCE-3+4).In terms of Isometric Tests , weakness in Extension is most often attributed to weakness in the Posterior Deltoid (SOURCE-4). All range of motion assessment should be compared to the asymptomatic side.
The following Shoulder - Special Tests may be relevant in the assessment of dysfunctional Extension: Glenohumeral Instability
Apprehension Test - evaluates end-range of Anterior Glenohumeral Joint Capsule
Load & Shift Test - evalautes the direction and degree of instability
Anterior Drawer Test (shoulder) - evaluate for anterior instability
Muscular Insufficiency
Lift-Off Test - assesses Subscapularis
Belly Press Test - assesses Subscapularis
Long Head of Biceps Pain / Integrity
Speed’s - assess for Tendinopathy or SLAP Lesion
Yergason’s - assess integrity of Tendon
Lateral Scapular Slide Test - measures distance between Scapula and Spine at various degress of elevation
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 , C6 , C7 , C8 and T1 Nerve Roots most relevant to Extension: Cervical - Myotomes (active resisted)
T1 - Hand Intrinsics
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 Extension 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-14).
Radiography (X-Ray)- evaluates Bone pathology which could mechanically block Extension. 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-15+16). MRIs are also the preferred technique for evaluating soft tissues such as the Rotator Cuff , Subacromial Bursa and associated morphologies (SOURCE-16). 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-16). For Subacromial Impingement the following view are recommended (SOURCE-16):
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 Extension dysfunction should be specific to the underlying cause. For rehabilitation of common underlying conditions such as Rotator Cuff or Long Head of Biceps pathology, Scapular Dyskinesis or Adhesive Capsulitis , see their respective pages.
As detailed underPathomechanics, the main points of focus of Stretching for Extension dysfunction are to restore length/ reduce tone in the Glenohumeral Joint Capsule and related ligamentous structures, particularly those found on the anterior shoulder and the GH Joint - Flexion Muscles . The following lists stretching techniques that may be directly or indirectly relevant:
Passive Prone Extension - practitioner passively moves arm into Extension, slight Elbow - Flexion may reduce limitations from a restricted Biceps Brachii
Door Frame Shoulder Stretch - self-guided anterior shoulder stretch with large Horizontal GH Joint - Abduction range
Split Stance Biceps Stretch - self-guided anterior shoulder stretch with large GH Joint - Extension range
Banded Capsule Rolls - split stance biceps variation that emphasises shoulder rotation
Shoulder Dislocates - mobility exercise that emphasises the greatest circumduction range possible
Wheel Pose - full bridge variation that lengthens entire anterior chain
Bretzel 1.0 - wholebody technical stretch that incorporates anterior shoulder
Bretzel 2.0 - variation with greater hip extension range
As a specific training protocol relates to the underlying cause of Extension dysfunction, the following lists Extension-based Strength exercises or those that incorporate a component of Extension in rough descending order from most rudimentary:
Active or Active Resisted Extension - may be prone to eliminate compensatory patterns or seated/ standing
Banded Unilateral Lat Activations - activate lat, posteroinferior drawer on Humerus
Circumduction Row - isotonic exercise with variable load used to emphasise mid-to-lower Trapezius
Bird-Dog - bodyweight isotonic exercise that emphasises Posterior Sling / Core
Seated Row - rudimentary weighted isotonic horizontal pull movement
One Arm Row - unilateral DB version of Seated Row
Straight Arm Lat Pulldown - isotonic motion that emphasises Lats and straight arm strength
Double Tricep Kickbacks - Triceps Brachii exercise that extends The Elbow and The Shoulder Girdle
Bent Over Row - weighted isotonic horizontal pull exercise that emphasises entire posterior chain
Dips - bodyweight isotonic push exercise with large GH Joint - Extension range
DB Pullover - moderate isotonic movement with large overhead and Thoracic - Extension range
Bird-Dog Row - One Arm Row variation that emphasises Posterior Sling
The following Mobilisation techniques may be relevant in the treatment of Extension: Joint Play
Posterior Glide on Humerus - stretches Anterior Glenohumeral Joint Capsule which may restrict Extension.Hand Behind Backvariation may also be of relevance
Lateral Distraction on Humerus - distraction of joint surfaces
Long Arm Traction on Humerus - less specific, may be more suited to global restrictions
Scapulothoracic Joint - during Extension the Inferior Angle of Scapula rotates medially (SOURCE-3)
Sternoclavicular Joint - during Extension the medial Clavicle glides superiorly (SOURCE-3)
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-17):
Mobilisation with Movement - as Extension is affected, mobilisations may benefit from the addition of movement:
Shoulder - MWM Techniques - Extension is a key component of many techniques, however, some may be more relevant than others. The following lists those movements that involve Flexion and other movements they’re paired with:
Shoulder - MWM 6 - Hand Behind Back, GH Internal Rotation
Shoulder - MWM 7 - Hand Behind Back, GH Internal Rotation
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-17)
Reverse NAGS - particularly useful for pain or restriction associated with movement of the Upper Thoracic region
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