Subacromial Impingement and Bursitis Info In-depth Evidence

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Overview

• Management of subacromial impingement syndrome includes physical therapy, injections, and surgery for some patients [1].
• There remains a need for high-quality studies of the pathology, etiology, and management of subacromial impingement syndrome [1].
• Current randomized, controlled trial evidence shows no difference in outcomes of shoulder function or pain between surgical and conservative treatment for subacromial impingement syndrome [3].
• Ultrasound guidance is not superior in subacromial bursa injections in pain or function [4].
• Ultrasound guidance is not superior in glenohumeral joint injections in pain or function [4].
• Subacromial pain syndrome should preferably be treated non-operatively [7].
• Subacromial injection with corticosteroids is indicated for persistent or recurrent symptoms of subacromial pain syndrome [7].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months in patients with shoulder impingement syndrome [11].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy at 5 years for patients with shoulder impingement syndrome [12].
• Arthroscopic subacromial decompression in the treatment of subacromial impingement yields good long-term results [13].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy on return to work in patients with shoulder impingement syndrome [14].
• Adding a large dose of shoulder strengthening to current nonoperative care for patients with subacromial impingement did not result in superior shoulder-specific patient-reported outcomes [15].
• For patients who have a long-term disease course, operative treatments may be considered [16].
• Standard ASD surgery is preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression [16].
• Preserving the subacromial bursa during rotator cuff surgery may lead to better rotator cuff healing when secondary pain is manageable [22].
• Arthroscopic subacromial decompression is a valid treatment, reducing pain and improving quality of life for patients selected for surgery according to the Danish national guidelines [29].

Anatomy & Pathophysiology

Bony Anatomy

• The proximal humerus comprises the humeral head, greater tuberosity, lesser tuberosity, and humeral shaft [35].
• The articular head of the humerus is spherical with a diameter of 37 to 57 mm [35].
• The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [35].
• Humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [35].
• The humeral head is inclined approximately 130 degrees with respect to the humeral shaft [35].
• The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps tendon [35].
• The distal aspect of the bicipital groove is internally rotated with respect to the proximal portion [35].
• The anatomic neck of the proximal humerus is located at the junction of the articular surface and the tuberosities [35].
• The surgical neck represents an indistinct region below the tuberosities but above the humeral shaft [35].
• The greater tuberosity is located in a posterior-superior location with respect to the humeral shaft and serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons [35].
• The lesser tuberosity is located on the anterior aspect of the proximal humerus and serves as the attachment site for the subscapularis tendon [35].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear [35].
• The glenoid cavity is a shallow socket, approximately one third the size of the humeral head [36].
• The neck-shaft angle measures an average of 135 degrees [36].
• The humeral head is retroverted an average of 30 degrees [36].
• The scapula is attached to the axial skeleton by the acromioclavicular and sternoclavicular joints [37].
• The scapular body is triangular when viewed anteroposteriorly, with its base situated superiorly and its apex inferiorly [37].
• The glenoid is connected with the flat body of the scapula by the scapular neck [37].
• The coracoid process curves forwards from the superior surface of the scapular neck [37].
• The acromion is a flattened bony process that curves forwards from the scapular spine [37].
• The lateral pillar connects the inferior border of the glenoid with the inferior angle of the scapula [37].
• The spinal pillar arises from the central part of the glenoid and continues medially to become part of the base of the scapular spine [37].
• The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa [37].
• The weakest area of the circumference of the biomechanical body of the scapula is the spinomedial angle [37].
• The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [38].
• Failure of fusion of the acromial ossification centers results in os acromiale [38].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [38].
• The humeral head averages 19° of retroversion and 41° of inclination (neck-shaft angle) [38].

Soft Tissue Anatomy

• The rotator cuff consists of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles [36].
• The teres major is not a rotator cuff muscle [36].
• The rotator cuff muscles serve as depressors of the humeral head to allow the deltoid to efficiently abduct the humerus [36].
• The infraspinatus and teres minor are external rotators of the humerus [36].
• The subscapularis is an internal rotator of the humerus [36].
• The acromion, coracoacromial ligament, and coracoid process form the coracoacromial arch [35].
• The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [35].
• The subscapular bursa lies between the subscapularis tendon and the neck of the scapula [39].
• The subscapular bursa communicates with the joint cavity between the superior and middle glenohumeral ligaments [39].
• The subscapular bursa is linked to the coracoid process by a suspensory ligament [39].
• In 28% of dissected specimens, the subscapular bursae merged with the subcoracoid bursae, forming a unique wide bursa [39].
• The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [38].
• The rotator interval contains the coracohumeral ligament, the superior glenohumeral ligament, and the intra-articular portion of the long head of the biceps tendon [38].
• The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [38].
• The superior glenohumeral ligament is a primary static restraint against anterior translation with the arm at the side [38].
• The coracohumeral ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [38].
• The middle glenohumeral ligament is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [38].
• The anterior band of the inferior glenohumeral ligament is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation [38].
• The posterior band of the inferior glenohumeral ligament is a primary static restraint against posterior-inferior translation in internal rotation and adduction [38].

Vascular Anatomy

• The proximal humerus receives its blood supply from the anterior and posterior humeral circumflex branches from the third division of the axillary artery [35].
• The posterior humeral circumflex artery travels with the axillary nerve, enters the quadrilateral space posteriorly, and anastomoses with a branch of the anterior circumflex to supply the posterior cuff [35].
• The anterior humeral circumflex artery arises from the axillary artery at the inferior border of the subscapularis [35].
• The anterior humeral circumflex artery provides vascular inflow to the humeral head by way of its terminal anterolateral branch known as the artery of Laing or arcuate artery [35].
• The ascending branch of the anterior humeral circumflex artery courses parallel to the lateral aspect of the long head biceps tendon and enters the humeral head at the interface of the bicipital groove and greater tuberosity [35].
• Injury to the arcuate artery may result in osteonecrosis of the humeral head [35].
• Additional extraosseous collateral branches can permit humeral head perfusion despite complete ligation of the arcuate artery [35].
• The major blood supply to the humeral head is through the ascending branch of the anterior humeral circumflex artery, which penetrates the head at the bicipital groove and becomes the arcuate artery [36].
• The anterolateral ascending branch of the anterior humeral circumflex artery provides the primary blood supply to the humeral head [38].
• The terminal intraosseous portion of the anterior humeral circumflex artery enters at the proximal aspect of the intertubercular groove as the arcuate artery [38].

Pathophysiology

• The pathophysiology of impingement syndrome may have both extrinsic and intrinsic components [31].
• The extrinsic theory of impingement is mechanical and related to the anatomy of the coracoacromial arch [31].
• Patients with a flat (type-I) acromion had better results than those with a curved (type-II) or hooked (type-III) acromion in non-operative treatment [31].
• In a population of patients with rotator cuff lesions, there was a decreased prevalence of type-I acromial morphology and an increased prevalence of type-III acromial morphology [31].
• The outcome for patients with a type-II acromion was not significantly different than that for patients with a type-III acromion [31].
• Neer divided the impingement process into three stages [31].
• Stage I of impingement is characterized by acute bursitis with subacromial edema and hemorrhage and is usually observed in patients who are thirty years old or less [31].
• Stage II of impingement is characterized by inflammation of the rotator cuff and possible partial-thickness tears, resulting from the subacromial bursa losing its ability to lubricate and protect the underlying rotator cuff [31].
• Stage III of impingement results in a full-thickness tear of the rotator cuff due to wear of the anterior aspect of the acromion on the greater tuberosity and supraspinatus tendon [31].
• The progressive process of impingement can be interrupted with an acromioplasty [31].
• The term 'subacromial impingement syndrome' as a useful diagnosis is increasingly questioned in the literature [54].
• There is an emerging consensus that symptoms ascribed to subacromial impingement syndrome may arise from a number of shoulder pathologies associated with the soft tissues occupying the subacromial space [54].
• Traditionally, extrinsic factors were proposed as causing compression and abrasion of the bursal side of the rotator cuff, mechanically encroached between the acromion (or coracoid) and humeral head [54].
• The traditional extrinsic model is being challenged with intrinsic rotator cuff pathology suggested as more causative of symptoms [54].
• Cadaver studies have demonstrated that rotator cuff pathology occurs more frequently within the internal substance or on the joint side of the tendon [54].
• Internal impingement syndrome is a painful shoulder condition related to the impingement of soft tissue, including the rotator cuff, joint capsule, long head of the biceps tendon, and glenoid labrum [25].
• Two types of internal impingement syndrome can be differentiated: posterior-superior impingement and anterior-superior impingement [25].
• The aetiology of anterior-superior internal impingement appears to be related to the pulley lesion and instability of the long head of the biceps tendon [25].
• Anterior-superior internal impingement can be caused by trauma or degenerative factors [25].
• Anterior-superior internal impingement produces anterior shoulder pain in middle-aged patients, particularly when performing overhead activities [25].
• Anterior-superior internal impingement is probably more frequent than previously reported [25].
• There is no evidence to prove the efficacy of a specific treatment for anterior-superior internal impingement [25].
• Imaging abnormalities of the acromioclavicular joint and subacromial space are common in asymptomatic shoulders [8].
• Due to low certainty of evidence and significant variation among study populations, further research is needed to clarify prevalence estimates of imaging abnormalities in asymptomatic shoulders [8].
• There was no between group difference in acromiohumeral distance in neutral shoulder position, shoulder abduction at 45° or 60° in adults with subacromial pain syndrome [18].
• Subacromial notching following reverse shoulder arthroplasty is not associated with functional outcomes or range of motion at short-term follow-up [19].
• Displaced proximal humeral fractures can impede normal movement of the rotator cuff, subacromial bursa, and subdeltoid bursa, causing impingement and disruption of normal glenohumeral motion [35].
• In proximal humeral fractures, the subdeltoid and subacromial bursae can become thickened and fibrotic, forming adhesions that can limit normal glenohumeral motion [35].
• Early range of motion exercises after a fracture have been hypothesized to decrease the formation of bursal adhesions [35].
• The pathogenesis of shoulder stiffness is still elusive, but ongoing basic science research has provided insight into cellular and biochemical pathways that result in shoulder stiffness [23].

Classification

• Patients presenting with signs and symptoms of subacromial pain syndrome have a high prevalence of conflicting and concomitant diagnoses [2].
• A comprehensive classification of individualized impingements occurring around the anterior aspect of the shoulder has been proposed to address conflicting theories and improve understanding of etiologic factors, diagnosis, and treatment [6].
• Subacromial osteolysis following hook plate fixation for acromioclavicular dislocation has a relatively high and variable incidence [17].
• The primary factor influencing the reported incidence of subacromial osteolysis following hook plate fixation is the radiological assessment method [17].
• In a cohort of 138 patients with calcium deposits, 46.4% had bilateral deposits, with calcium visible in a total of 202 shoulders [66].
• Among patients with unilateral calcium deposits, the right shoulder was involved twice as often as the left [66].
• 51.5% of involved shoulders had calcium in the supraspinatus portion of the cuff [66].
• 44.5% of involved shoulders had calcium in the infraspinatus portion of the cuff [66].
• 23.3% of involved shoulders had calcium in the teres minor portion of the cuff [66].
• Only 5 shoulders showed calcium in the subscapularis [66].
• Calcium was visible in the subacromial bursa in 25 shoulders [66].
• There were 41 shoulders with an acute attack of bursitis in the cohort described by [66] [66].

Clinical Presentation

• Night pain is a common complaint of patients presenting with impingement of the shoulder [51].
• Night pain cannot be used in isolation as a diagnostic predictor for the presence of a rotator cuff tear [51].
• Women aged between 30 and 60 years with subacromial pain syndrome and a calcific deposit of >1.5 cm in length have the highest chance of suffering from symptomatic calcific tendinopathy of the rotator cuff [20].
• Examination of the cervical spine in patients with subacromial shoulder pain is variable in randomized controlled trials [27].

Investigations

Diagnostic Challenges and Clinical Assessment

• The history and physical examination are paramount in the diagnosis of a stiff shoulder, with ancillary studies helpful in certain circumstances [23].
• A Cochrane review includes 33 studies evaluating a total of 4002 shoulders in 3852 patients regarding physical tests for shoulder impingements and local lesions [5].

Radiography

• At least two X-ray views should be obtained: an anteroposterior in the plane of the glenoid and an axillary projection with the arm in abduction to show the relationship of the humeral head to the glenoid [43].
• Standardized plain films are almost always sufficient to garner the information needed for shoulder evaluation [24].
• The anteroposterior view in the plane of the scapula shows the superoinferior position of the humeral head relative to the glenoid, presence of osteophytes, narrowing of the joint space, and degree of medial displacement of the humerus [24].
• The axillary view taken with the arm in the functional position of elevation is referred to as the "truth view" because it demonstrates glenohumeral relationships in the functional position [24].
• The standardized axillary view enables the measurement of posterior subluxation or "functional decentering" that is not evident in images taken with the arm at the side [24].
• Due to the low certainty of evidence and significant variation among study populations, further research is needed to clarify prevalence estimates of imaging abnormalities in asymptomatic shoulders [8].

Magnetic Resonance Imaging

• Magnetic resonance imaging is useful to identify osteonecrosis of the humeral head, bone tumours, labral tears, and rotator cuff tears [43].
• The accuracy of MRI for identifying labral tears and rotator cuff tears is enhanced by combining the scan with arthrography [43].
• The acromiohumeral distance is significantly smaller in MRI compared to AP radiographs in shoulders with an intact rotator cuff [70].
• The acromiohumeral distance should not be used as a decision criterion on MRI to assess glenohumeral centering or subacromial space width in shoulders with an intact rotator cuff [70].
• Diagnostic and therapeutic practices regarding internal impingement of the shoulder differ between surgeons, with international surgeons favoring MRI [62].

Ultrasound

• Ultrasound is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [43].
• Ultrasound can be useful in guiding injections or barbotage [43].
• Ultrasound guidance is not superior in subacromial bursa and glenohumeral joint injections in pain or function [4].
• The subacromial space width is smaller in nearly all rotator cuff pathologies and becomes even smaller as the severity of the condition increases [74].
• The subacromial space width is smaller in the case of a complete cuff tear [74].
• Machine learning-based ultrasomics may be helpful in the preliminary screening of shoulder pain for subacromial impingement syndrome stages [73].

Computed Tomography and Arthroscopy

• Computed tomography is helpful for planning fracture surgery and shoulder joint replacement [43].
• French surgeons rely more on CT-arthrography for internal impingement of the shoulder compared to international surgeons [62].
• Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum, and rotator cuff tears [43].
• CT scans may offer increased precision in the measurement of glenoid version, but this precision does not necessarily improve the quality of surgery or clinical outcome [24].

Treatment

Non-Operative Management

• Management of subacromial impingement syndrome includes physical therapy and injections [1].
• Most management regimes for subacromial impingement employ a minimum period of 12 weeks of conservative management incorporating physiotherapy and at least 2 subacromial steroid injections [10].
• There is little reproducible evidence to support the efficacy of subacromial corticosteroid injection in managing rotator cuff disease [58].

Injections

• Ultrasound guidance is not superior in subacromial bursa and glenohumeral joint injections regarding pain or function [4].

Operative Management

• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months for patients with shoulder impingement syndrome [11].
• For patients who have a long-term disease course, operative treatments may be considered, with standard ASD surgery preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression [16].
• Five randomized trials found that formal subacromial decompression does not result in improved clinical outcomes up to 2 years after rotator cuff repair [30].
• ASD in the treatment of subacromial impingement yields good long-term results [13].
• There is no evidence from the available RCTs for differences in outcome in pain and shoulder function between conservatively and surgically treated patients with subacromial impingement syndrome [32].
• No clinically meaningful differences in pain or function were found between surgery plus physiotherapy and physiotherapy alone at 3-, 6-months, 1-, 2-, 5- or ≥10-years follow up [47].
• The evidence on effectiveness of surgical or conservative treatment of shoulder impingement was found to be limited based on the review of seven RCTs [49].

Complications

Post-operative Outcomes and Long-term Effects

• Arthroscopic subacromial decompression yields good long-term results in the treatment of subacromial impingement [13].
• Major improvements in pain and function were observed at mid- to long-term follow-up after isolated arthroscopic subacromial decompression and combined decompression with rotator cuff repair [28].
• There was no evidence of progression of intrinsic rotator cuff pathologic conditions at a mean follow-up of 4.5 years following acromioplasty without repair for partial-thickness rotator cuff tears [34].

Surgical Complications and Anatomical Changes

• Subacromial osteolysis has a relatively high and variable incidence following hook plate fixation for acromioclavicular dislocation, with the primary factor influencing reported incidence being the radiological assessment method [17].
• Subacromial notching is not associated with functional outcomes or range of motion at short-term follow-up when it occurs following reverse shoulder arthroplasty with a 135° inlay humeral component and a lateralized glenoid [19].

Diagnostic and Pathological Complications

• Synovitis in the subacromial space was milder and not associated with any clinical parameters in patients with rotator cuff tears [9].

Recovery

Non-Operative Management

• Variation exists in the management regimes offered to patients with subacromial impingement, but most employ a minimum period of 12 weeks of conservative management incorporating physiotherapy and at least 2 subacromial steroid injections [10].
• Adding a large dose of shoulder strengthening exercises to nonoperative care for 16 weeks did not significantly improve long-term outcomes in terms of shoulder disability, health-related quality of life, sick leave, or surgery rates at 1 year [33].
• More than half of patients diagnosed with subacromial pain syndrome in specialist care settings do not adhere to recommendations regarding duration of exercise-therapy, but this is not related to symptom improvement [26].

Operative Management

• Major improvements in pain/function were seen at mid- to long-term after isolated arthroscopic subacromial decompression and combined decompression/rotator cuff repair [28].

Diagnostic and Anatomical Considerations

• Synovitis in the subacromial space was milder and not associated with any clinical parameters [9].
• There was no between group difference in acromiohumeral distance (AHD) in neutral shoulder position, shoulder abduction at 45° or 60° [18].

Key Evidence

• [L5] Management of subacromial impingement syndrome includes physical therapy, injections, and surgery for some patients, but there remains a need for high-quality studies of the pathology, etiology, and management of the condition. [1] (10.5435/00124635-201111000-00006)
• [L3] Patients presenting with signs and symptoms of subacromial pain syndrome have a high prevalence of conflicting and concomitant diagnoses. [2] (10.1177/23259671251332942)
• [L1] Current randomized, controlled trial evidence shows no difference in outcomes of shoulder function or pain between surgical and conservative treatment for subacromial impingement syndrome. [3] (10.2106/jbjs.9202.ebo579)
• [L1] Ultrasound guidance is not superior in the subacromial bursa and glenohumeral joint injections in pain or function. [4] (10.1016/j.arthro.2021.12.013)
• [L1] The review includes 33 studies evaluating a total of 4002 shoulders in 3852 patients. [5] (10.1002/14651858.cd007427.pub2)
• [L4] The article proposes a comprehensive classification of all individualized impingements occurring around the anterior aspect of the shoulder, including newly described entities, to address conflicting theories and improve understanding of their etiologic factors, diagnosis, and treatment. [6] (10.1007/s00264-017-3515-1)
• [Paper] SAPS should preferably be treated non-operatively, with subacromial injection with corticosteroids indicated for persistent or recurrent symptoms. [7] (10.3109/17453674.2014.920991)
• [L2] Due to the low certainty of evidence and significant variation among study populations, further research is needed to clarify these prevalence estimates and to guide evidence-based management of shoulder abnormalities. [8] (10.1186/s13018-024-05378-4)
• [L4] Synovitis in the subacromial space was milder and not associated with any clinical parameters. [9] (10.1177/23259671231207818)
• [L4] Variation exists in the management regimes offered to patients with subacromial impingement, but most employ a minimum period of 12 weeks of conservative management incorporating physiotherapy and at least 2 subacromial steroid injections. [10] (10.1177/1758573215571010)
• [L1] In this controlled trial involving patients with a shoulder impingement syndrome, arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months. [11] (10.1136/bmj.k2860)
• [L1] Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy at 5 years for patients with shoulder impingement syndrome. [12] (10.1136/bjsports-2020-102216)
• [L3] ASD in the treatment of subacromial impingement yields good long-term results. [13] (10.1016/j.jse.2007.06.020)
• [L1] Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy on return to work in patients with shoulder impingement syndrome. [14] (10.1186/s12891-021-04768-7)
• [L1] Adding a large dose of shoulder strengthening to current nonoperative care for patients with subacromial impingement did not result in superior shoulder-specific patient-reported outcomes. [15] (10.1177/03635465211016008)
• [L1] For patients who have a long-term disease course, operative treatments may be considered, with standard ASD surgery preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression. [16] (10.1097/md.0000000000000510)
• [L1] Subacromial osteolysis has a relatively high and variable incidence, and the primary factor influencing the reported incidence is the radiological assessment method. [17] (10.1016/j.jse.2024.03.018)
• [L1] There was no between group difference in acromiohumeral distance (AHD) in neutral shoulder position, shoulder abduction at 45° or 60°. [18] (10.1038/s41598-020-76704-z)
• [L3] When subacromial notching occurs, it is not associated with functional outcomes or range of motion at short-term follow-up. [19] (10.1016/j.jseint.2024.01.009)
• [L3] This study demonstrates that women aged between 30 and 60 years with subacromial pain syndrome and a calcific deposit of >1.5 cm in length have the highest chance of suffering from symptomatic calcific tendinopathy of the rotator cuff. [20] (10.1016/j.jse.2015.02.024)
• [L5] Preserving the subacromial bursa during rotator cuff surgery may lead to better rotator cuff healing when secondary pain is manageable. [22] (10.1530/eor-2024-0183)
• [L4] [25] (10.1007/s00167-010-1232-z)
• [L3] More than half of patients diagnosed with subacromial pain syndrome in specialist care settings do not adhere to recommendations regarding duration of exercise-therapy, but this is not related to symptom improvement. [26] (10.1016/j.msksp.2021.102322)
• [L1] Examination of the cervical spine in patients with subacromial shoulder pain is variable in randomized controlled trials. [27] (10.1177/1758573218798023)
• [L3] Major improvements in pain/function were seen at mid- to long-term after isolated arthroscopic subacromial decompression and combined decompression/rotator cuff repair. [28] (10.1016/j.jor.2018.03.004)
• [L4] Arthroscopic subacromial decompression is a valid treatment, reducing pain and improving quality of life for patients selected for surgery according to the Danish national guidelines. [29] (10.1016/j.jse.2017.03.028)
• [L1] Five randomized trials found that formal subacromial decompression does not result in improved clinical outcomes up to 2 years after rotator cuff repair. [30] (10.1016/j.arthro.2012.06.003)
• [L3] [31] (10.2106/00004623-199705000-00013)
• [L1] According to the best-evidence synthesis, there is no evidence from the available RCTs for differences in outcome in pain and shoulder function between conservatively and surgically treated patients with SIS. [32] (10.1016/j.jse.2009.01.010)
• [L1] Adding a large dose of shoulder strengthening exercises to nonoperative care for 16 weeks did not significantly improve long-term outcomes in terms of shoulder disability, health-related quality of life, sick leave, or surgery rates at 1 year. [33] (10.1177/23259671251374314)
• [L4] There was no evidence of progression of intrinsic rotator cuff pathologic conditions at a mean follow-up of 4.5 years. [34] (10.1177/03635465020300021801)
• [L1] [47] (10.1371/journal.pone.0216961)
• [L1] Based on the review of seven RCTs, the evidence on effectiveness of surgical or conservative treatment of shoulder impingement was found to be limited. [49] (10.3109/09638288.2014.907364)
• [L3] Night pain is a common complaint of patients presenting with impingement of the shoulder but cannot be used in isolation as a diagnostic predictor for the presence of a rotator cuff tear. [51] (10.1111/j.1758-5740.2011.00133.x)
• [L1] [54] (10.1177/1758573216660038)
• [L1] This systematic review of the available literature indicates that there is little reproducible evidence to support the efficacy of subacromial corticosteroid injection in managing rotator cuff disease. [58] (10.5435/00124635-200701000-00002)
• [L4] Diagnostic and therapeutic practices regarding internal impingement of the shoulder differ between surgeons in France and in other countries, with French surgeons relying more on CT-arthrography and intra-articular injections, while international surgeons favor MRI and physical therapy. [62] (10.1016/j.otsr.2019.09.007)
• [L4] [66] (10.1001/jama.1941.02820220019004)
• [L4] The acromiohumeral distance is significantly smaller in the MRI in comparison to AP radiographs in shoulders with an intact rotator cuff and should not be used as a decision criterion on MRI to assess glenohumeral centering or subacromial space width. [70] (10.1007/s00167-020-06090-6)
• [L4] This noninvasive and low-cost approach may be helpful in the preliminary screening of shoulder pain. [73] (10.1002/jum.15914)
• [L4] The subacromial space width is smaller in nearly all rotator cuff pathologies, but becomes even smaller as the severity of the condition increases and is smaller in the case of a complete cuff tear. [74] (10.1016/j.ultras.2003.11.015)

References

[1] Subacromial Impingement Syndrome. American Academy of Orthopaedic Surgeon. 2011. DOI: 10.5435/00124635-201111000-00006

[2] The Challenge of Diagnosing Patients Presenting With Signs and Symptoms of Subacromial Pain Syndrome: A Descriptive Study of 741 Patients Seen in a Secondary Care Setting. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251332942

[3] Current Evidence Fails to Show Differences in Effectiveness Between Conservative and Surgical Treatment of Subacromial Impingement Syndrome. The Journal of Bone & Joint Surgery. 2010. DOI: 10.2106/jbjs.9202.ebo579

[4] Ultrasound Guidance Is Not Superior in Subacromial Bursa and Intraarticular Injections but Superior in Bicipital Groove: A Meta-analysis of Randomized Controlled Trials. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2022. DOI: 10.1016/j.arthro.2021.12.013

[5] Physical tests for shoulder impingements and local lesions of bursa, tendon or labrum that may accompany impingement. Cochrane Database of Systematic Reviews. 2013. DOI: 10.1002/14651858.cd007427.pub2

[6] Redefining anterior shoulder impingement: a literature review. International Orthopaedics. 2017. DOI: 10.1007/s00264-017-3515-1

[7] Guideline for diagnosis and treatment of subacromial pain syndrome. Acta Orthopaedica. 2014. DOI: 10.3109/17453674.2014.920991

[8] Imaging abnormalities of the acromioclavicular joint and subacromial space are common in asymptomatic shoulders: a systematic review. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-024-05378-4

[9] Clinical Implication of Glenohumeral and Subacromial Synovitis in Rotator Cuff Tears. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671231207818

[10] Current UK practices in the management of subacromial impingement. Shoulder & Elbow. 2015. DOI: 10.1177/1758573215571010

[11] Subacromial decompression versus diagnostic arthroscopy for shoulder impingement: randomised, placebo surgery controlled clinical trial. BMJ. 2018. DOI: 10.1136/bmj.k2860

[12] Subacromial decompression versus diagnostic arthroscopy for shoulder impingement: a 5-year follow-up of a randomised, placebo surgery controlled clinical trial. British Journal of Sports Medicine. 2020. DOI: 10.1136/bjsports-2020-102216

[13] Small full-thickness tears do well ten to thirteen years after arthroscopic subacromial decompression. Journal of Shoulder and Elbow Surgery. 2008. DOI: 10.1016/j.jse.2007.06.020

[14] Return to work after subacromial decompression, diagnostic arthroscopy, or exercise therapy for shoulder impingement: a randomised, placebo-surgery controlled FIMPACT clinical trial with five-year follow-up. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04768-7

[15] Effectiveness of Adding a Large Dose of Shoulder Strengthening to Current Nonoperative Care for Subacromial Impingement: A Pragmatic, Double-Blind Randomized Controlled Trial (SExSI Trial). The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211016008

[16] Treatments for Shoulder Impingement Syndrome. Medicine. 2015. DOI: 10.1097/md.0000000000000510

[17] Subacromial osteolysis following hook plate fixation for acromioclavicular dislocation: a systematic review and meta-analysis. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2024.03.018

[18] No relationship between the acromiohumeral distance and pain in adults with subacromial pain syndrome: a systematic review and meta-analysis. Scientific Reports. 2020. DOI: 10.1038/s41598-020-76704-z

[19] Rates of subacromial notching are low following reverse shoulder arthroplasty with a 135° inlay humeral component and a lateralized glenoid. JSES International. 2024. DOI: 10.1016/j.jseint.2024.01.009

[20] Prevalence of calcific deposits within the rotator cuff tendons in adults with and without subacromial pain syndrome: clinical and radiologic analysis of 1219 patients. Journal of Shoulder and Elbow Surgery. 2015. DOI: 10.1016/j.jse.2015.02.024

[22] Removal or retention: evolving views on possible roles of the subacromial bursa in rotator cuff disease. EFORT Open Reviews. 2025. DOI: 10.1530/eor-2024-0183

[23] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > SUMMARY.

[24] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > Radiographic Evaluation.

[25] Anterior‐superior internal impingement of the shoulder: an evidence‐based review. Knee Surgery, Sports Traumatology, Arthroscopy. 2010. DOI: 10.1007/s00167-010-1232-z

[26] Less than half of patients in secondary care adheres to clinical guidelines for subacromial pain syndrome and have acceptable symptoms after treatment: A Danish nationwide cohort study of 3306 patients. Musculoskeletal Science and Practice. 2021. DOI: 10.1016/j.msksp.2021.102322

[27] Screening of the cervical spine in subacromial shoulder pain: A systematic review. Shoulder & Elbow. 2018. DOI: 10.1177/1758573218798023

[28] Long-term results after surgical treatment of subacromial pain syndrome with or without rotator cuff tear. Journal of Orthopaedics. 2018. DOI: 10.1016/j.jor.2018.03.004

[29] Acromioplasty in patients selected for operation by national guidelines. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2017.03.028

[30] The Changing Role of Acromioplasty. Arthroscopy. 2012. DOI: 10.1016/j.arthro.2012.06.003

[31] Non-Operative Treatment of Subacromial Impingement Syndrome. The Journal of Bone and Joint Surgery (American Volume)*. 1997. DOI: 10.2106/00004623-199705000-00013

[32] Conservative or surgical treatment for subacromial impingement syndrome? A systematic review. Journal of Shoulder and Elbow Surgery. 2009. DOI: 10.1016/j.jse.2009.01.010

[33] The Effect of Adding a Large Dose of Shoulder Strengthening to Nonoperative Care for Subacromial Impingement on Shoulder Disability, Quality of Life, Sick Days, and Surgery Rates: 1-Year Results From a Pragmatic, Double-Blind Randomized Controlled Trial (SExSI). Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251374314

[34] The Partial-Thickness Rotator Cuff Tear: Is Acromioplasty without Repair Sufficient?. The American Journal of Sports Medicine. 2002. DOI: 10.1177/03635465020300021801

[35] Rockwood And Matsen S The Shoulder. Shoulder and Elbow Specialty Clinic Workers’ Survey > ANATOMY.

[36] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 2Musculoskeletal Trauma Surgery > SHOULDER AND ARM INJURIES.

[37] Rockwood And Green S Fractures In Adults. 29: Principles of Nonunion and Bone Defect Treatment > Applied Anatomy Related to Scapular Fractures.

[38] Aaos Comprehensive Orthopaedic Review 3. Anatomy of the Shoulder, Arm, and Elbow > I. Shoulder.

[39] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Bursae.

[43] Apley And Solomon S Concise System Of Orthopaedics And Trauma. INVESTIGATION.

[47] The effectiveness of surgical vs conservative interventions on pain and function in patients with shoulder impingement syndrome. A systematic review and meta-analysis. PLOS ONE. 2019. DOI: 10.1371/journal.pone.0216961

[49] Conservative treatment or surgery for shoulder impingement: systematic review and meta-analysis. Disability and Rehabilitation. 2014. DOI: 10.3109/09638288.2014.907364

[51] Night Pain is not a useful Diagnostic Indicator of Cuff Tear in Patients with Symptoms of Subacromial Impingement. Shoulder & Elbow. 2011. DOI: 10.1111/j.1758-5740.2011.00133.x

[54] Electromyographic activity of the shoulder muscles during rehabilitation exercises in subjects with and without subacromial pain syndrome: a systematic review. Shoulder & Elbow. 2016. DOI: 10.1177/1758573216660038

[58] The Efficacy of Subacromial Corticosteroid Injection in the Treatment of Rotator Cuff Disease: A Systematic Review. Journal of the American Academy of Orthopaedic Surgeons. 2007. DOI: 10.5435/00124635-200701000-00002

[62] Internal impingement of the shoulder: An international survey of 261 orthopaedic surgeons. Orthopaedics & Traumatology: Surgery & Research. 2019. DOI: 10.1016/j.otsr.2019.09.007

[66] CALCIUM DEPOSITS IN THE SHOULDER AND SUBACROMIAL BURSITIS. Journal of the American Medical Association. 1941. DOI: 10.1001/jama.1941.02820220019004

[70] The acromiohumeral distance in the MRI should not be used as a decision criterion to assess subacromial space width in shoulders with an intact rotator cuff. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06090-6

[73] Machine Learning‐Based Ultrasomics for Predicting Subacromial Impingement Syndrome Stages. Journal of Ultrasound in Medicine. 2021. DOI: 10.1002/jum.15914

[74] Sonographic evaluation of subacromial space. Ultrasonics. 2004. DOI: 10.1016/j.ultras.2003.11.015