Shoulder impingement

Welcome to the first in a series of blog posts about shoulder issues and how Drop Release can help improve your management of them.  As always, if you have questions or comments, please reach out to us by following the contact us link.

The shoulder is a huge focus of the Drop Release approach, as it is critical to our everyday activities.  Additionally, it is closely related to the function of the cervical and thoracic spine as well as the rib cage.  The concept of regional interdependence also connects shoulder function to hip and lower body function through the numerous kinetic chains that include the shoulder.  That stated, let’s dive into our first shoulder topic – subacromial impingement syndrome.

Subacromial Impingement Syndrome, SAIS, what is it, why does it matter, how can we identify it, and how do we treat it?  And lastly, how can Drop Release help us be more efficient and effective at treating it?

Subacromial impingement syndrome is defined as abnormal contact between the ceiling of the subacromial space and the soft tissues within the space.  There are several subcategories of SAIS to consider.

Primary SAIS involves direct compression of rotator cuff tendons between the humeral head and the acromion, coracoacromial ligaments, the coracoid process, and the acromioclavicular joint. (2). This type is often caused by suboptimal bony morphology, such as type 3 acromion or abnormal healing after a humeral head fracture.

Secondary SAIS results from anterior instability due to loosening of the capsule and labrum from repetitive motions such as overhead work or throwing.  Due to increased numeral head translation, the biceps tendon and rotator cuff can become impinged secondary to the ensuing instability. (2)  This type is more related to abnormal alignments or neuromuscular control of shoulder movement.  It can also be caused by suboptimal positioning of the thoracic spine and cage, as well as poor scapular control.  This is the type of SAIS that is most easily addressed and reversed in a manual therapy setting.

Internal impingement results from repetitive shoulder activity in 90+ degrees of abduction and 90+ degrees of external rotation.  This position brings the supraspinatus and infraspinatus tendons further posterior and can cause them to rub on the posterosuperior glenoid rim / lip.  They can then be impinged between this part of the glenoid and the humeral head. (2)

Impingement syndrome is important to identify and address because if left alone, it can progress to rotator cuff tears and eventual failure of the shoulder joint.  In fact, Neer stated that 95% of rotator cuff tears are caused by SAIS.  We don’t know what percentage of impingements progress to that point, but if we can catch them early and reverse the course we can help many of our patients avoid major surgical intervention down the road.  Shoulder pain is the 3rd leading cause of presentation to a MSK provider, and while 23% of new onset shoulder pain resolves within 6 months, over 50% lasts for over 12 months.  That is a very high level of chronicity and carries with it all the biopsychosocial impacts of chronic pain.  When we consider that SAIS is the number one cause of shoulder pain, the importance of identifying and addressing it becomes even clearer.

All subtypes of SAIS feature decreased subacromial space and abnormal contact between the boundaries of the space and the soft tissues within.  There are other commonalities as well that contribute to SAIS.  These include posterior shoulder tightness (6), forward shoulder posture and forward head posture (10), increased thoracic kyphosis and lack of thoracic extension ROM (11).  Virtually all cases of SAIS also feature and may result from scapular dyskinesis- which is the topic of next week’s blog.

Diagnosing SAIS is a process of identifying common symptoms and then applying a cluster of orthopedic tests to diagnose the condition and the subtype in order to drive treatment.

The most common complaints in SAIS include anterolateral shoulder pain between 70 and 120 degrees of elevation, pain with overhead movements, and pain when lying on the affected side.  

Inspection of a patient suspected of SAIS may reveal forward shoulder posture characterized by scapular protraction, anterior tilt, and internal rotation (tight pectoralis minor, tight posterior shoulder girdle), internal shoulder rotation (tight subscapularis), forward head posture (more consistent in women), increased thoracic kyphosis with decreased extension, and lack of humeral depression with elevation.

Physical examination is over 90% specific for identifying SAIS when the Neer’s, Hawkins-Kennedy, Jobe (bilateral empty can), and painful arc tests are used.  In fact, Neer’s test alone is 86% sensitive for SAIS, so if it is negative the likelihood of SAIS decreases to 14%.  Once SAIS is identified, it is important to discover whether or not joint hypermobility is a contributing factor.  This can be determined by the sulcus sign, apprehension test / relocation test, and a Beighton hypermobility index >5 (there is a lack of consensus in the literature on the cutoff).  If imaging becomes necessary, diagnostic ultrasound has emerged as the go-to modality for ruling out rotator cuff pathology.

Treatment of the SAIS patient should include thoracic spine manipulation to improve extension, and cervical spine manipulation as indicated by findings.  Shoulder manipulation should be minimized in cases of hypermobility syndrome, though joint centration must be addressed.  Soft tissue treatment to address and normalize rotator cuff muscles, posterior shoulder capsule, pectoralis minor and upper trapezius (which is often overly active in these patients) is also essential.  Home rehabilitation exercise is also needed and should include exercises to improve posterior scapular strength, activation of middle and lower trapezius, as well as stretches / mobilizations to improve flexibility of pectoralis minor, posterior shoulder capsule, and thoracic extension.

Using the Drop Release instrument in the management of SAIS has several advantages over traditional treatment.  First, both the muscles involved and the posterior shoulder capsule can be treated at the same time in the same position with no stress on the practitioner’s body.  Second, full ROM can be achieved in mere minutes, allowing more time to be spent on other aspects of the visit, such as teaching active care exercises.  The video below shows an actual shoulder patient being treated with the Drop Release instrument to address muscle tightness in the infraspinatus, teres group, subscapularis, pectoralis minor, as well as tightness in the posterior shoulder capsule.  Pre and post treatment passive ROM is demonstrated, as is patient ROM in the “sleeper stretch,” which targets the posterior shoulder capsule.  We also show pre and post measurement of forward shoulder posture through a modification of the “double square” approach in which a sheet of paper on a clipboard is used to mark the starting and finishing of the anterior edge of the acromion in relation to a wall against which the patient is standing.

Originally the Drop Release approach just targeted the muscles around the joint in question.  However, research has shown us that ligaments and joint capsules also contain golgi tendon organs, the target of the Drop Release’s mechanism of action.  This has led us to address the capsule directly, and the results can be incredible, as seen in the video.  We hope you enjoyed this post and found some pearls to add to your shoulder approach.   


  1.  Hunter et al.  Shoulder Impingement Syndrome and Thoracic Posture.  Phys The.  2020 Apr 17; 100(4):677-686.
  2. Ellenbecker, Cools.  Rehabilitation of shoulder impingement syndrome and rotator cuff injuries: an evidence-based review.  Br J Sports Med 2010; 44:319-327.
  3. Koc, et al.  Mechanoreceptors observed in a ligamentous structure between the posterior horn of the lateral meniscus and the anterior cruciate ligament.  Knee Surg Sports Traumatol Arthrosc.  2020.
  4. Backenkohler et al.  Topography of mechanoreceptors in the shoulder joint region- a computer-aided 3D reconstruction in the laboratory mouse.  Anat Rec 1997 248:433-441.
  5. Laumonerie et al.  Sensory innervation of the human shoulder joint: the three bridges to break., Journal of Shoulder and Elbow Surgery (2020)
  6. Launder et al.  Posterior shoulder tightness and subacromial impingement characteristics in baseball pitchers: a blinded, matched control study.  Int J Sports Phys Ther.  2020 Apr;15(2):188-195.
  7. Oyama et al.  Asymmetric resting scapular posture in healthy overhead athletes.  J Athl Train.  2008;43(6):565-570.
  8. Struyf et al.  Scapulothoracic muscle activity and recruitment timing in patients with shoulder impingement symptoms and glenohumeral instability.  J Electromogr Kinesiol 2014;24:277-284.
  9. Garving et al.  Impingement syndrome of the shoulder.  Dtsch Arztebl Int 2017;114:765-76.
  10. Alizadehkhaiyat et al.  Postural alterations in patients with subacromial impingement syndrome.  Int J Sports Phys Ther.  2017;12(7):1111-1120.
  11. Park, et al.  Effects of thoracic mobilization and extension exercise of thoracic alignment and shoulder function in patients with subacromial impingement syndrome: a randomized controlled pilot study.  Healthcare 2020 Sept 2;8:316-327.

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