Subacromial Impingement

Subacromial Impingement Syndrome, abbreviatedSIS, describes a mechanical compression of the Subacromial Space and the sequelae that follows. This space within The Shoulder Girdle defined by the underside of the Acromion (proximally) and Head of Humerus (inferiorly). Subacromial Impingement is either considered primary or secondary. The former results from a structural narrowing of the Subacromial Space and the latter from perturbed Glenohumeral arthrokinematics which impinge the local soft-tissues. Subacromial Impingement Syndrome accounts for roughly 36-74% of Pain instances in The Shoulder Girdle (SOURCE-11).

Pathomechanics

Primary

Primary Impingementresults from a structural narrowing of the Subacromial SpaceTypically seen in patients over the age of 40. Potential causes includes:

  • Bony Narrowing

    • Osteophytes under Acromioclavicular Joint - formation on the Acromial Facet or anteroinferior surface may narrow the Subacromial Space and has been associated with a greater risk of SIS (SOURCE-24). A local environment of Inflammation may trigger or perpetuate Osteophyte growth which may be developed from Subacromial Bursitis or degeneration of the Acromioclavicular Ligaments or Coracoacromial Ligament (SOURCE-24). Osteophyte formation is considerably more common in those over 50 or those who repeatedly engage in overhead (shoulder elevation) movements (SOURCE-24)

    • Hooked Acromion of Scapula - the lower acromial tilt angle seen in Hooked Acromion morphologies can reduce the Subacromial Space and has been associated with a greater risk of SIS and Rotator Cuff pathology (SOURCE-24). One study reported those with a Hooked Acromion were 6.2 times more likely to develop SIS when compared to a Flat Acromion (SOURCE-24). This morphology has an estimated prevalence of 12% in the general population which increases in males and those over the age of 40 (SOURCE-24)

  • Soft Tissue Inflammation - shoulder lesions can narrow the Subacromial Space by 53-68% (SOURCE-23)

Secondary

Secondary Impingement- perturbed arthrokinematics at the Glenohumeral Joint from several causes leads to entrapment of the soft tissues. Typically seen in younger populations ~15-35 years old (SOURCE-17):

Impingement

Once impinged the soft tissues share a similar cascade, as described by Neer (SOURCE-1 (30)) in three stages:

  1. Acute Subacromial Bursitis and other signs of Inflammation

  2. Insufficient lubrication from Bursa leads to Rotator Cuff Tendinopathy - Anterior Supraspinatus often develops early signs of damage or Tear

  3. Damage progresses to full-thickness Tear

Either a predisposing factor or sequela of Subacromial Impingement is altered positioning and Motor Control of the Scapula (SOURCE-4 (5,6)). A reduction in Scapulothoracic Joint - Upward Rotation or Posterior Scapular Tilting during arm elevation, for example, is thought to reduce the Subacromial Space and predispose tissue injury or prolong recovery (SOURCE-12). Similarly, excessive Internal Rotation of the Scapula or elevation of the Clavicle with Anterior Scapular Tilting may increase the risk of impingement (SOURCE-12+13).The primary contributor to abnormal Scapula kinematics and consequent impingement is altered Connective Tissue or Muscle tone, most notably of the following (SOURCE-5):

  • Hypertonic (overactive)

    • Upper Trapezius - over activity of the upper fibres is common and often labeled as a general compensatory response to shoulder pathology; however, the associated increase in SC Joint - Elevation causes Anterior Scapular Tilting which provides a mechanism for Impingement (SOURCE-14).

    • Pectoralis Minor - when shorted this muscle produces an Internal Rotation and Anterior Scapular Tilting bias, resulting in Scapular Kinematics similar to that seen in impingement (SOURCE-15). Therefore it has been postulated shortening of this muscle can lead to a reduction in the Subacromial space by restricting posterior tilting of the Scapula (SOURCE-4)

    • Posterior Glenohumeral Joint Capsule - may lead to excessive anterosuperior translation of the Humeral Head during movements such as GH Joint - Flexion or GH Joint - Internal Rotation

    • Latissimus Dorsi - hypertonicity may lead to a destabilising inferior pull on the Humeral Head (SOURCE-32)

  • Hypotonic (under active)

    • Serratus Anterior - those with impingement display significantly less lower Serratus Anterior activation, some postulating it may be a predisposing factor (SOURCE-14).

    • Latissimus Dorsi - affords an inferior bias to the Humeral Head to maintain the subacromial space (SOURCE-20). Therefore, hypotonicity may lead a narrowing of the space and consequent impingement

    • Rotator Cuff - pre-fatigue of these muscles displayed an acute narrowing of the Subacromial Space of 2-14mm or 6-40% of the total space. This has been attributed to a failure of this muscle group to counter the superior bias of the Deltoid (SOURCE-23)

    • Long Head of Biceps - Given the inferior distraction force the LHB is thought to produce on the Head of the Humerus , the Biceps are considered to play a degenerative role in the onset of impingement (SOURCE-9)

    • Middle + Lower Trapezius - When appropriately toned, the orientation of the middle fibres are suited to offset the lateral bias of the upper Serratus Anterior and the lower fibres are most suited for Scapulothoracic Joint - Upward Rotation . Together the Mid-to-Lower fibres stabilise and Externally Rotate the Scapula (SOURCE-14)

Pathology

The following pathologies share relations with Subacromial Impingement, often serving as predisposing or maintaining factors or resulting from chronic impingement:

Scapular Dyskinesis - described as a compensatory response to Pain in The Shoulder Girdle and has been associated with a reduction in the Subacromial space (SOURCE-4). Decreased Scapulothoracic Joint - Upward Rotation and Posterior Scapular Tilting during shoulder elevation appear to be the most consistent findings; while increased Internal Rotation was among other pathomechanics reported (SOURCE-12+27)

Thoracic Spine Kyphosis - associated with pathomechanics of the Scapula which predispose impingement (SOURCE-27)

Cervical Spine Radiculopathy - can lead to Rotator Cuff weakness and Subacromial Impingement (SOURCE-8 (63)). One study found 1/4 of impingement cases to display signs of a Cervical Radiculopathy, with 5.3% indicating a C5 / C6 Radiculopathy (SORUCE-8 (65)).

Subacromial Bursitis - inflammation of the Subacromial Bursa plays an integral role in the early pathogenesis of impingements. One hypothesis for the evolution of Subacromial Bursitis into Impingement attributes synovial folds, known asPlica. These Plica course through the Bursa and may increase friction of the Rotator Cuff (SOURCE-10)

Long Head of Biceps Tendinopathy / Tear - the severity of impingement is correlated with severity of Long Head of Biceps Tendon degeneration, which is attributed to mechanical (friction/ compression) and inflammatory mechanisms (SOURCE-28)

Glenohumeral Instability - shares a complex, reinforcing and often bidirectional relationship with Subacromial Impingement. The implied insufficient action from the Rotator Cuff may lead to excessive superior translation of the Head of Humerus which reduces the subacromial space either at rest or through movements such as arm elevation. Conversely, chronic impingement increases friction on muscles such as the Rotator Cuff and Long Head of Biceps on their course through the subacromial space and compromises their ability to accurately centre the Humeral Head within the Glenoid Fossa, leading to instability.

Diabetes - in the elderly diabetics display a notable increase in rotator cuff tendon thickness which may narrow the Subacromial Space and predispose impingement (SOURCE-26)

Referred Pain

The Referred Pain pattern for Subacromial Impingement is similar to any Subacromial Pain , referring to the Lateral Acromion/ Deltoid and the posterior upper arm (SOURCE-8 (33)).

Differential Diagnosis

Assessment

Observation

Range of Motion

In terms of Range of Motion , shoulder elevation ( GH Joint - Abduction or GH Joint - Flexion ) is often restricted by Pain (SOURCE-11).

Orthopaedic Tests

The following Shoulder - Special Tests can be used to evaluate for impingement or distinguish from other conditions:

Anterior

Posterior

Other Special Tests , particularly those for the Rotator Cuff , may be relevant for evaluating tissues which may contribute to impingement.

Length Testing

The following Muscles are likely shortened/ restricted in Subacromial Impingement:

Strength Testing

Manual Muscle Testing of the following muscles may be indicated as the following Muscles could be weak or inhibited in Subacromial Impingement:

Fascia

There are several Fascia l connections that may be implicated in Subacromial Impingement:

Symptoms of Pain or restriction at any point along either fascial line or chain may indicate dysfunction and provide direction for treatment.

Imaging

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-29).

Radiographs- Generally the first line of imaging, used to determine presence of bony abnormalities of the Coracoacromial Arch with the following views of particular relevance (SOURCE-2+3+24):

  • 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:

  • Outlet view - reveals morphology of the Acromion

  • Axillary view - evaluates for Os Acromiale

When X-Ray findings are unremarkable, CT Scans and MRI’s may be indicated (SOURCE-24).

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-12+29). MRIs are also the preferred technique for evaluating soft tissues such as the Rotator Cuff , Subacromial Bursa and associated morphologies (SOURCE-29). 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-29). For Subacromial Impingement the following view are recommended (SOURCE-29):

  • 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

Ultrasonography (Ultrasound)- an accessible imaging modality with real-time capabilities for the evaluation of Subacromial Impingement via certain metrics (SOURCE-29+30):

  • 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 - as measured by the Acromio-Humeral Distance (AGT), between the inferolateral edge of the Acromion of Scapula and the Apex of the Greater Tubercle of Humerus . AGT was found to be significantly decreased in SIS shoulders when compared to asymptomatic sides and controls. A side-to-side differential of <2.1mm was considered normal

  • Rotator Cuff Tendon Thickness - a decrease in tendon thickness was associated with Subacromial Impingement which is indicative of degenerative changes associated with chronicity

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-30). AStandard II (longitudinal plane) Viewmay be used to determine the AGT distance with the Humerus neutrally rotated (SOURCE-30). Other views that may be relevant include Standard Auxiliary Views I, II and III (SOURCE-30).

Computed Tomography (CT) Scan- akin to MR-arthrography, used most often for the evaluation of Cartilage or the Glenoid Labrum (SOURCE-29). Typically reserved as a complement to other imaging modalities for the assessment of bony changes or when MRI’s are contraindicated (SOURCE-29).

Treatment

The initial phases of treatment should focus on reducing tone of the hypertonic structures and increasing tone of the hypotonic structures. Once this is achieved treatment can then progress to developing functional patterns such as the muscle couplings discussed above to eventually reflect the tasks seen in their sport or activities of daily living.

Stretching

Stretching of the Scapulothoracic Joint musculature has been shown to improve position of the Scapula (SOURCE-4 (17,18)). Further stretching regimes have reduced Pain and disability in those with impingement (SOURCE-16). As a general trend anterior shoulder/ Chest stretches are recommended for the general populations while posterior shoulder stretches for the overhead athete (SOURCE-36):

Strengthening

Strength training forms an integral part of the conservative management and rehabilitation of Subacromial Impingement. With such an array of underlying causes and contributing factors strengthening of Muscles local to The Shoulder Girdle may be indicated, notably those discussed below:

  • Scapula Stabilsers - either a predisposing factor or sequela of impingement is altered positioning/ motor control of the Scapula (SOURCE-4). Strengthening of the musculature that affords stability to the Scapulothoracic Joint has been supported as a relevant treatment for Subacromial Impingement as evaluated by markers such as Pain and disability (SOURCE-4+33):

    • Serratus Anterior - reduced activity of the Serratus Anterior has been displayed in several pathologies of The Shoulder Girdle including impingement (SOURCE-7). As a major Scapula stabiliser both weakness and excessive tone/ restriction have the capacity to foster secondary impingement

    • Trapezius - the relation with impingement is multifactoral and continguent on the fibre orientation. With their ability to Posteriorly Tilt the Scapula , the Lower fibres may decrease impingement risk while altered recruitment of the Upper and Middle fibres is often assocaited with impingement (SOURCE-5). Training of the Lower fibres is particularly relevant where impingement is associated with overhead athletes (SOURCE-25)

    • Rhomboids - through their primary Scapulothoracic Joint - Retraction function, serve as an imporant agonist to the Serratus Anterior . Insufficent action may lead to an impingement mechanism derived from excessive Scapulothoracic Joint - Protraction or abduction. During overhead motions insufficient retraction may also increase stresses on the anterior shoulder (SOURCE-34)

    • Levator Scapulae - while more often discussed in the context of overactivity, insufficiency may disturb Scapula positioning and ultimately the length-tension relationship of other Scapula stabilisers

  • Glenohumeral Joint Stabilisers

    • Rotator Cuff - shares a bidirectional relationship with impingement. Both primary and secondary impingment threaten the integrity of the rotator cuff. Conversely, Rotator Cuff insufficiency leads to a failure to centre the Head of the Humerus in the Glenoid Fossa and counter the superior bias of the Deltoid , both of which predispose Subacromial Impingement. In either instance rehabilitation is relevant and should include both strengthening and Proprioception exercises

    • Long Head of Biceps - shares a similar bidirectional relationship with impingement as the Rotator Cuff

  • Prime Movers

    • Latissimus Dorsi - affords an inferior bias on the Head of the Humerus that maintains the Subacromial Space (SOURCE-20). Excessive tone in the posterior shoulder, which includes the Latissimus Dorsi, also leads to altered mechanics such as Scapulothoracic Joint - Protraction and/ or Anterior Tilting of the Scapula (SOURCE-35). This suggests while strengthening of this muscle is important, exercise selections should emphasise a large range of motion

    • Deltoid - unlike the compressive action of the Rotator Cuff, the Deltoids generate substantial superior shear forces which either stabilise or destabilise the Humerus depending on contextual factors such as arm position and exernal load (SOURCE-19). The Deltoids notable resistance to inferior translation of the humerus increasingly diminishes as the arm elevates (SOURCE-19)

Initial Phase - the primary goal of this phase is to relieve Pain and Inflammation and to normalise Range of Motion (SOURCE-36). Provocative activities and poor posture should be avoided and strength exercises should be carefully progressed from rudimentary exercises such as Isometrics, as tolerated by the patient (SOURCE-36). The patient maybe progressed from this stage once the Painful Arc is eliminated and muscular balance/ dynamic stability is restored (SOURCE-36):

Mid-Phase - while avoiding reaggrivation of symptoms, the goals of this phase include reestablishing non-painful Range of Motion and Strength (SOURCE-36). Proper arthrokinematics of The Shoulder Girdle should be promoted as too for activites with the affected arm (SOURCE-36). For the most part, overhead lifting and other activities should still be avoided (SOURCE-36):

Late Phase - involves multipoint compound exercises performed dynamically, typically reflecting the functional motions performed in their sport or activities of daily living (SOURCE-25). In this phase full, non-painful Range of Motion and Strength should be achieved (SOURCE-36):

Myofascial Release

Once the acute response of Inflammation has subsided, Myofascial Release techniques may be of benefit for those with Subacromial Impingement to improve markers of Pain , Range of Motion , Muscle Strength and functionality/ disability (SOURCE-36+37). Generally speaking the pracitioner should search for tender points along a muscle where there is an area of increased tissue resistance and sustain pressure until the patient experiences a decline or release in tension (SOURCE-38). While many local muscles may have contributing tender points, those hypertonic muscles included in thePathomechanicssection are most likely implicated. With that in mind, the following details muscles that are specifically described to benefit from myofascial techniques in those with impingement:

  • Trapezius - the myofascial release of the Upper Trapezius in those with Subacromial Impingement has shown to improve all aforementioned symptoms, in particular Range of Motion where it was shown to be more effective than Proprioceptive Neuromuscular Facilitation techniques (SOURCE-37). One described myofascial technique involved a sustained pressure, glided along the length of the sacromeres (SOURCE-37). Similar techniques applied to the Middle and Lower Trapezius did not display the same effect (SOURCE-38)

Mobilisation

Mobilisation techniques to The Shoulder Girdle , Cervical Spine , Thoracic Spine are often used as a compliment to Strength training and Stretching , typically boasting additonal benefits including a greater reduction in Pain and improvements in tissue extensibility/ Range of Motion (SOURCE-36). A reverse capsular pattern is often present where GH Joint - Internal Rotation is most restricted, followed by GH Joint - Abduction and then GH Joint - External Rotation (SOURCE-36). In earlier phases, grade I and II mobilisations may neuromodulate pain through the stimulatuion of Mechanoreceptors , while in the later stages of rehabilitation higher-grade mobilisations play a more mechanical role in addressing specific joint restrictions and maintaining optimal arthrokinematics (SOURCE-36). The following techniques may be relevant in the treatment of Subacromial Impingement with pain usually serving as an effective guide for technique application intensity: Joint Play

Mobilisation with Movement

Surgery

Subacromial Decompression (acromioplasty/ bursectomy) is a common surgical intervention for Rotator Cuff pathology and other causes of Subacromial Impingement that removes bone spurs from the anterolateral undersurface of the Acromion and inflamed Subacromial Bursa or other soft tissues with the aim of widening the space for traversing Tendons (SOURCE-40+41+42). Decompression may be achieved through an open approach, arthroscopic-assisted (mini-open) or arthroscopic only with the latter resulting in less morbidity and shorter recovery times (SOURCE-40). Despite being common, the use of this procedure remains controversial as it boasts no or negligible benefits for markers such as Pain , functionality and quality of life when compared to placebo surgery or exercise therapy (SOURCE-40+41+42). Additionally the lack of extra benefit comparing open decompression to arthroscopic decompression suggests the benefits of surgery may be attributed to either the placebo effect or post-operative physiotherapy (SOURCE-41).

Other

Other modalities that may be relevant in the treatment of Subacromial Impingement include:

  • Cryotherapy - through vasoconstriction reduces metabolic activity and consequently Inflammation (SOURCE-36). Additionally, Cryotherapy increases the Pain threshold which decreases pain perception (SOURCE-36). These mechanisms may be particularly relevant in the acute stage of injury

  • Heat - following the acute inflammatory stage, heat may be used to improve tissue pliability to enhance certain treatment modalities such as Stretching or Myofascial Release (SOURCE-36)

  • Kinesiology Tape (KT) - has been shown to decrease Pain and increase Range of Motion that relates to impingement, with its effects on pain lasting up to a month post treatment (SOURCE-38)

References

  1. Harrison, A. K., & Flatow, E. L. (2011). Subacromial impingement syndrome. The Journal of the American Academy of Orthopaedic Surgeons, 19(11), 701–708. https://doi.org/10.5435/00124635-201111000-00006

  2. Alqunaee, M., Galvin, R., & Fahey, T. (2012). Diagnostic accuracy of clinical tests for subacromial impingement syndrome: a systematic review and meta-analysis. Archives of physical medicine and rehabilitation, 93(2), 229–236. https://doi.org/10.1016/j.apmr.2011.08.035

  3. Koh, K. H., Han, K. Y., Yoon, Y. C., Lee, S. W., & Yoo, J. C. (2013). True anteroposterior (Grashey) view as a screening radiograph for further imaging study in rotator cuff tear. Journal of shoulder and elbow surgery, 22(7), 901–907. https://doi.org/10.1016/j.jse.2012.09.015

  4. Struyf, F., Nijs, J., Mottram, S., Roussel, N. A., Cools, A. M., & Meeusen, R. (2014). Clinical assessment of the scapula: a review of the literature. British journal of sports medicine, 48(11), 883–890. https://doi.org/10.1136/bjsports-2012-091059

  5. Park, S.-y., & Yoo, W.-g. (2011). Differential activation of parts of the serratus anterior muscle during push-up variations on stable and unstable bases of support. Journal of Electromyography and Kinesiology, 21(5), 861–867. https://doi.org/10.1016/j.jelekin.2011.07.001

  6. Hamada, J., Igarashi, E., Akita, K., & Mochizuki, T. (2008). A cadaveric study of the serratus anterior muscle and the long thoracic nerve. Journal of Shoulder and Elbow Surgery, 17(5), 790–794. https://doi.org/10.1016/j.jse.2008.02.009

  7. Cools, A. M. J., Struyf, F., De Mey, K., Maenhout, A., Castelein, B., & Cagnie, B. (2014). Rehabilitation of scapular dyskinesis: From the office worker to the elite overhead athlete. British Journal of Sports Medicine, 48(8), 692–697. https://doi.org/10.1136/bjsports-2013-092148

  8. Katsuura, Y., Bruce, J., Taylor, S., Gullota, L., & Kim, H. J. (2020). Overlapping, masquerading, and causative cervical spine and shoulder pathology: A systematic review. Global Spine Journal, 10(2), 195–208. https://doi.org/10.1177/2192568218822536

  9. Chen, H. W., & Chew, F. S. (2006). Complete rupture of both heads of the biceps brachii muscle belly by blunt trauma. Radiology Case Reports, 1(4), 145–148. https://doi.org/10.2484/rcr.v1i4.28

  10. Kennedy, M. S., Nicholson, H. D., & Woodley, S. J. (2017). Clinical anatomy of the subacromial and related shoulder bursae: A review of the literature. Clinical anatomy (New York, N.Y.), 30(2), 213–226. https://doi.org/10.1002/ca.22823

  11. Chaimongkhol, T., Benjachaya, S., & Mahakkanukrauh, P. (2020). Acromial morphology and morphometry associated with subacromial impingement syndrome. Anatomy & cell biology, 53(4), 435–443. https://doi.org/10.5115/acb.20.166

  12. Ludewig, P. M., & Reynolds, J. F. (2009). The association of scapular kinematics and glenohumeral joint pathologies. Journal of Orthopaedic & Sports Physical Therapy, 39(2), 90–104. https://doi.org/10.2519/jospt.2009.2808

  13. Paley, K. J., Jobe, F. W., Pink, M. M., Kvitne, R. S., & ElAttrache, N. S. (2000). Arthroscopic findings in the overhand throwing athlete: Evidence for posterior internal impingement of the rotator cuff. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 16(1), 35–40. https://doi.org/10.1016/S0749-8063(00)90125-7

  14. Phadke, V., Camargo, P. R., & Ludewig, P. M. (2009). Scapular and rotator cuff muscle activity during arm elevation: A review of normal function and alterations with shoulder impingement.Brazilian Journal of Physical Therapy, 13(1), 1–12. https://doi.org/10.1590/S1413-35552009005000012

  15. Borstad, J. D., & Ludewig, P. M. (2005). The effect of long versus short pectoralis minor resting length on scapular kinematics in healthy individuals. Journal of Orthopaedic & Sports Physical Therapy, 35(4), 227–238. https://doi.org/10.2519/jospt.2005.35.4.227

  16. Turgut, E., Duzgun, I., & Baltaci, G. (2018). Stretching Exercises for Subacromial Impingement Syndrome: Effects of 6-Week Program on Shoulder Tightness, Pain, and Disability Status. Journal of Sport Rehabilitation, 27 (2), 132-137. Retrieved Dec 9, 2025, from https://doi.org/10.1123/jsr.2016-0182

  17. Garving, C., Jakob, S., Bauer, I., Nadjar, R., & Brunner, U. H. (2017). Impingement Syndrome of the Shoulder. Deutsches Arzteblatt international, 114(45), 765–776. https://doi.org/10.3238/arztebl.2017.0765

  18. Hengeveld, E., & Banks, K. (Eds.). (2005). Maitland’s peripheral manipulation (4th ed.). Elsevier Butterworth-Heinemann.

  19. Mulla, D. M., Hodder, J. N., Maly, M. R., Lyons, J. L., & Keir, P. J. (2020). Glenohumeral stabilizing roles of the scapulohumeral muscles: Implications of muscle geometry. Journal of biomechanics, 100, 109589. https://doi.org/10.1016/j.jbiomech.2019.109589

  20. Sizer, P. S., Jr., Phelps, V., & Gilbert, K. (2003). Diagnosis and management of the painful shoulder. Part 1: Clinical anatomy and pathomechanics. Pain Practice, 3(1), 39–57. https://doi.org/10.1046/j.1533-2500.2003.00005.x

  21. Yeşilyaprak, S. S., Yüksel, E., & Kalkan, S. (2016). Influence of pectoralis minor and upper trapezius lengths on observable scapular dyskinesis. Physical Therapy in Sport, 19, 7–13. https://doi.org/10.1016/j.ptsp.2015.08.002

  22. Umehara, J., Nakamura, M., Nishishita, S., Tanaka, H., Kusano, K., & Ichihashi, N. (2018). Scapular kinematic alterations during arm elevation with decrease in pectoralis minor stiffness after stretching in healthy individuals. Journal of shoulder and elbow surgery, 27(7), 1214–1220. https://doi.org/10.1016/j.jse.2018.02.037

  23. Teyhen DS, Miller JM, Middag TR, Kane EJ. Rotator Cuff Fatigue and Glenohumeral Kinematics in Participants Without Shoulder Dysfunction. Journal of Athletic Training. 2008;43(4):352–358. doi: 10.4085/1062-6050-43.4.352

  24. Chaimongkhol, T., Benjachaya, S., & Mahakkanukrauh, P. (2020). Acromial morphology and morphometry associated with subacromial impingement syndrome. Anatomy & cell biology, 53(4), 435–443. https://doi.org/10.5115/acb.20.166

  25. Adachi G, Oshikawa T, Akuzawa H, Kaneoka K. Muscle Activity During Scapular Muscle Exercises With Multijoint Compound Movement: Analysis Using Fine-Wire and Surface Electrodes. Orthopaedic Journal of Sports Medicine. 2022;10(11). doi:10.1177/23259671221132194

  26. Abate, M., Schiavone, C., & Salini, V. (2010). Sonographic evaluation of the shoulder in asymptomatic elderly subjects with diabetes. BMC musculoskeletal disorders, 11, 278. https://doi.org/10.1186/1471-2474-11-278

  27. Association between kyphosis and subacromial impingement syndrome: LOHAS study. (PDF).

  28. Can, F. İ., Gültaç, E., Şahin, İ. G., Kılınç, C. Y., & Hürriyet Aydoğan, N. (2022). Subacromial impingement as a predictor of proximal biceps tendon disorders. Joint diseases and related surgery, 33(1), 142–148. https://doi.org/10.52312/jdrs.2022.499

  29. Jäschke, M., Köhler, H. C., Weber, M. A., Tischer, T., Hacke, C., & Schulze, C. (2023). Subacromial impingement syndrome: association of multiple magnetic resonance imaging parameters with shoulder function and pain. Archives of orthopaedic and trauma surgery, 143(1), 237–246. https://doi.org/10.1007/s00402-021-04032-6

  30. Cholewinski, J. J., Kusz, D. J., Wojciechowski, P., Cielinski, L. S., & Zoladz, M. P. (2008). Ultrasound measurement of rotator cuff thickness and acromio-humeral distance in the diagnosis of subacromial impingement syndrome of the shoulder. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 16(4), 408–414. https://doi.org/10.1007/s00167-007-0443-4

  31. Pesquer, L., Borghol, S., Meyer, P., Ropars, M., Dallaudière, B., & Abadie, P. (2018). Multimodality imaging of subacromial impingement syndrome. Skeletal radiology, 47(7), 923–937. https://doi.org/10.1007/s00256-018-2875-y

  32. Ruiz Ibán, M. A., Díaz Heredia, J., García Navlet, M., Serrano, F., & Santos Oliete, M. (2017). Multidirectional Shoulder Instability: Treatment. The open orthopaedics journal, 11, 812–825. https://doi.org/10.2174/1874325001711010812

  33. Ravichandran, H., Janakiraman, B., Gelaw, A. Y., Fisseha, B., Sundaram, S., & Sharma, H. R. (2020). Effect of scapular stabilization exercise program in patients with subacromial impingement syndrome: a systematic review. Journal of exercise rehabilitation, 16(3), 216–226. https://doi.org/10.12965/jer.2040256.128

  34. Paine, R., & Voight, M. L. (2013). The role of the scapula. International journal of sports physical therapy, 8(5), 617–629.

  35. Laudner, K. G., Moline, M. T., & Meister, K. (2010). The relationship between forward scapular posture and posterior shoulder tightness among baseball players. The American journal of sports medicine, 38(10), 2106–2112. https://doi.org/10.1177/0363546510370291

  36. Escamilla, R. F., Hooks, T. R., & Wilk, K. E. (2014). Optimal management of shoulder impingement syndrome. Open access journal of sports medicine, 5, 13–24. https://doi.org/10.2147/OAJSM.S36646

  37. Çelik, M. S., Sönmezer, E., & Acar, M. (2022). Effectiveness of proprioceptive neuromuscular facilitation and myofascial release techniques in patients with subacromial impingement syndrome. Somatosensory & motor research, 39(2-4), 97–105. https://doi.org/10.1080/08990220.2021.2018293

  38. Singh, H., Thind, A., & Mohamed, N. S. (2022). Subacromial Impingement Syndrome: A Systematic Review of Existing Treatment Modalities to Newer Proprioceptive-Based Strategies.Cureus,14(8), e28405. https://doi.org/10.7759/cureus.28405

  39. Kellam P, Kahn T, Tashjian RZ. Anatomy of the Subscapularis: A Review. Journal of Shoulder and Elbow Arthroplasty. 2019;3. doi:10.1177/2471549219849728

  40. Caddick, J., O’Connor, R., & Rangan, A. (2019). Subacromial decompression surgery for rotator cuff disease. Cochrane Database of Systematic Reviews, 2019(1), Article CD005619. https://doi.org/10.1002/14651858.CD005619.pub3

  41. Beard, D. J., Rees, J. L., Cook, J. A., Rombach, I., Cooper, C., Merritt, N., & Collins, G. S. (2018). Arthroscopic subacromial decompression for subacromial shoulder pain (CSAW): A multicentre, pragmatic, parallel group, placebo-controlled, three-group, randomised surgical trial. The Lancet, 391(10118), 329–338. https://doi.org/10.1016/S0140-6736(17)32457-1

  42. Lähdeoja T, Karjalainen T, Jokihaara J, et alSubacromial decompression surgery for adults with shoulder pain: a systematic review with meta-analysisBritish Journal of Sports Medicine 2020;54:665-673.

Related Articles

Seated Thoracic Rotation with Breathing

Posted on December 22, 2025

The Seated with is a tehcnique used to increase the available active Rotation . The following s likely experience on the side contralateral (opposite) to the direction of rotation: Starting Position: Rotation is first performed to establish a baseline and the presence of any asymmetries. The exercise is then performed with the following sequence: This sequence can be repeated several times each di

Shoulder Girdle

Posted on December 19, 2025

The Shoulder Girdle is comprised of 3 joints and 2 functional articulations, with only one point of direct contact with the axial skeleton. It’s ball-and-socket construction facilitates maximum range of motion in all three planes of movement making it the most mobile joint in the body (SOURCE-7); however, this is at the expense of its stability. Muscles of the shoulder complex provide the dynamic

Deep Front Line

Posted on December 15, 2025

The Deep Front Line is one of several proposed by Thomas Myers (SOURCE-1). As its name suggests this line lies deep of the , and . While the extensive integration of deep tissues allows this line to operate in all three dimensions, only atic is a movement that is primarily and uniquely generated by this line (SOURCE-1). The Deep Front Line is predominantly associated with slower-twitch s, which su