Q: What Causes Subacromial Impingement Syndrome?

A: Subacromial Impingement Syndrome occurs when the subacromial space is narrowed and weak structures in that space get compressed. There are several causes for subacromial impingment such as:

•Anatomical variations: The shape of the acromion plays an important role: There are 3 types of acromial shapes can be distinguished: (4)

•Type I: flat shape

•Type II: curved shape

•Type III: hooked shape (most likely to contribute to impingement and irritation)

Also Bony spurs also known as osteophytes at the bottom aspect of the acromion can also be involved.

•Rotator cuff weakness, causing the humeral head to drift superior or higher.

•Chronic rotator cuff irritation due to overuse.

•Posterior GH capsule tightness

•Poor posture (forward shoulder posture can cause functional narrowing of Subacromial space)

•Abnormal muscle activation

Definition: Subacromial impingement Syndrome is defined as "the mechanical compression of subacromial structures between the coraco-acromial arch and the humerus during active elevation of the arm above shoulder height."(2)

Clinically Relevant Anatomy:

Structures involved in subacromial impingment:

•the coracoacromial arch composed of acromion, processus coracoideus and ligamentum coracoacromiale

•the humerus

•the tendons of the Rotator Cuff 

•the long head of biceps brachii

•the subacromial bursa

•shoulder capsule

The subacromial space is the margin between the superior portion of the humeral head and the inferior portion of the acromion. It contains: (3)

•belly and tendon of the supraspinatus muscle

•long head of the biceps muscle

•subacromial bursa

1. Kachingwe AF, Phillips B, Sletten E, Plunkett SW. Comparison of Manual Therapy Techniques with Therapeutic Exercise in the Treatment of Shoulder Impingement: A Randomized Controlled Pilot Clinical Trial. The Journal of Manual fckLRManipulative Therapy 2008;16(4):238-­‐247

2. TATE A.R., MCCLURE P.W., YOUNG I.A., SALVATOR R., MICHENER L.A. Comprehensive impairment-based exercise and manual therapy intervention for patients with subacromial impingement syndrome: a case series. The Journal of orthopaedic and sports physical therapy. 2010 Aug; 40(8): 474-93

3. BIRRER R.B., O’CONNOR F.G. Sports medicine for the primary care physician. 3rd edition, Boca Raton: RCR PRESS, 2004.p507- 10

4. Bigliani LU, Morrison DS, April EW. The morphology of the acromion and its relationship to rotator cuff tears. Orthop Trans 1986;10:228.

Q: What are the Symptoms of Subacromial Impingement Syndrome?

A: The Symptoms of Subacromial Impingement Syndrome are shoulder pain during active elevation of the arm (usually reported at the anterior or lateral side of the shoulder). The onset is more of a gradual, degenerative process rather than due to an injury or strong external force. Therefore, patients have difficulty determining the exact time of when the shoulder pain began. 

Classification of the Impingement Syndrome

•First stage:

o   Moderate pain during exercise overhead

o   No loss of strength

o   No limitation in movement

o   Involves edema and/or hemorrhage.

o   This stage most commonly occurs in patients less than 25 years of age, but can be older 

o   Frequently associated with an overuse injury.

o   Generally, at this stage the syndrome is reversible.

•Second stage:

o   Pain during Activities of Daily Living; especially during the night time

o   Loss of mobility

o   Stage II is more advanced than Stage I and tends to occur in patients 25 to 40 years of age.

o   Progressive Deterioration of the tissues of the rotator cuff

•Third stage:

o   Strong restriction in movement due to calcifications

o   Loss of muscle strength

o   Stage III occurs in patients over 40-50 years of age and

o   Frequently involves a tendon rupture or tear.

o   Mechanical Dysfunction from the culmination of fibrosis and tendinosis that has been present for many years.

Neer CS 2d. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. J Bone Joint Surg [Am] 1972;54:41-50.

Q: What will my shoulder examination look like?

There are multiple diagnosis that can come from an examination of the shoulder. This is due to the complexity of the shoulder and multiple components that allow us to use our shoulder in the manner we do. Therefore, to better treat subacromial impingemnt syndrome (SIS), a proper diagnosis should be confirmed through examination.

Examination of the shoulder starts with a subjective history taking of the pain and functional deficits. Patient's with primary SIS generally present with pain at night, pain with overhead activities, and complaints of stiffness. Patient's with secondary SIS are typically of younger age, present with history of instability, pain with overhead activities, and/or are an overhead athlete.(1) When this subjective information is taken down this will help confirm SIS is present with objective physical examination.

Due to the multiple diagnosis that can come from the shoulder there are multiple tests that can be conducted. If SIS is suspected there are certain test that should be performed. With each examination a postural assessment, shoulder range of motion, and muscle strength should be taken. Possible special tests for SIS that can be used are as follows: Neer sign, Hawkins-Kennedy sign, painful arc sign, supraspinatus test, speed test, cross-body adduction test, drop-arm test, and infraspinatus test. It has been noted though by Park et al. that if three of these test (Hakwins-Kennedy sign, painful arc, and infraspinatus test) are positive then there is post test probability of high value (95%) that impingement is present. (2) Another study by Bang et al. indicated there were five test that should be performed: Hawkins-Kennedy sign, Neer sign, painful arc, supraspinatus test, infraspinatus test. If 3 or more of these test were positive then the likelihood of SIS being present increases. (3) It was also noted in this same study that the most reliable single test are painful arc, external rotation or infraspinatus test, and empty can or supraspinatus test.

Bottom Line

When undergoing an evaluation and examination of the shoulder for possible SIS there are varying ways to help rule in or rule out SIS. When SIS is suspected the following should be included to increase the likelihood of proper diagnosis and treatment:

• Detailed subjective history
• Postural assessment
• Range of motion
• Manual muscle testing (MMT)
• Special test:
  • Hawkins-Kennedy sign
  • Neer Sign
  • Painful arc (can be assessed during range of motion)
  • Infraspinatus or external rotation testing
  • Supraspinatus or empty can testing

1. Robertson, E. Current best evidence for the diagnosis and treatment of subacromial impingement syndrome. Lecture. Evidence in Motion. 2011.
2. Park HB, Yokota A, Gill HS, et al. Diagnostic Accuracy of Clinical Tests for the Different Degrees of Subacromial Impingment Syndrome. Journal of Bone and Joint Surgery. July 2005; 87-A; 7; 1446-1455
3. Michener LA, Walsworth MK, Doukas WC, et al. Reliability and Diagnostic Accuracy of 5 Phyiscal Examination Test and Combination Tests for Subacromial Impingement. Arch Phys Med Rehabil 2009;

Q.What are some of the other diagnostic tools that are used? How good are they to confirm diagnosis?

A.Impingement Syndrome is commonly diagnosed by clinical findings, subjective history in addition to diagnostic findings seen through MRI, Ultrasound and MR arthrography.

Jesus et al in their meta analysis compared MRI , Ultrasound and MR arthrography for rotator cuff tears. They found that MR arthrography was the most sensitive and specific of the three. However they also found MRI and Ultrasound to be comparable in both specificity and sensitivity. (1)

Shahabpour et al in their meta- analysis found that, for the shoulder impingement syndrome and rotator cuff tears, MRI and US have a comparable accuracy for detection of full-thickness rotator cuff tears. MRA and US might be more accurate for the detection of partial-thickness tears than MRI. Given the large difference in cost of MR and US, ultrasound may be the most cost-effective diagnostic method for identification of full-thickness tears in a specialist hospital setting.(2)

Bottom Line

•  MRI , MR arthrography and Ultrasound are commonly used diagnostic tools and their effectiveness is comparable.
• MR arthrography is the most sensitive.
• Ultrasound is the most cost-effective.

References

1. de Jesus JO, Parker L, Frangos AJ, Nazarian LN. Accuracy of MRI, MR arthrography, and ultrasound in the diagnosis of rotator cuff tears: a meta-analysis. AJR Am J Roentgenol. 2009 Jun;192(6):1701-7. PubMed PMID: 19457838. 
2. Shahabpour M, Kichouh M, Laridon E, Gielen JL, De Mey J. The effectiveness of diagnostic imaging methods for the assessment of soft tissue and articular disorders of the shoulder and elbow. Eur J Radiol. 2008 Feb;65(2):194-200. Review. PubMed PMID: 18312783

Q: What will I know after my examination?

A lot of things just happened in a short amount of time in that examination of your shoulder. So what does it all mean? If during your examination it was found that there is limitations in your range of motion, weakness and/or pain is present with empty can and external rotation testing, and pain is present with Neer sign and Hawkins-Kennedy, with a painful arc; it is likely that SIS is present. (1,2) If these signs and symptoms are not present or are inconclusive further evaluation and testing should be performed. If SIS is suspected and confirmed then a course of physical therapy treatment will commence; refer to “What Should PT consist of?” blog.

1. Park HB, Yokota A, Gill HS, et al. Diagnostic Accuracy of Clinical Tests for the Different Degrees of Subacromial Impingment Syndrome. Journal of Bone and Joint Surgery. July 2005; 87-A; 7; 1446-1455
2. Michener LA, Walsworth MK, Doukas WC, et al. Reliability and Diagnostic Accuracy of 5 Phyiscal Examination Test and Combination Tests for Subacromial Impingement. Arch Phys Med Rehabil 2009; 90.

Q: Should I get an Injection?

A: Winters et al (1) compared exercise, manual therapy, and corticosteroid injection for shoulder pain patients.  Patients with pain and limited range of motion in one or more directions that was due to dysfunction in specific joint structures and patients with pain and slightly limited range of motion not stemming from specific joint structures were placed in groups.  Those with dysfunction related to the glenohumeral joint itself benefitted most from injection while those with dysfunction stemming from movement dysfunction of the whole shoulder girdle (shoulder blade, thoracic spine, cervical spine), benefitted most from manual physical therapy.

Crawshaw et al (2) compared the effectiveness of subacromial injection with exercise and manual therapy to exercise and manual therapy alone for pain and disability of the shoulder for 12 weeks.  After 1 week the patients receiving injection and therapy felt significant better than the group receiving only therapy.  After 12 weeks, however, there was no significant difference between these two groups of patients in change in total pain and disability.


Bottom line: Subacromial corticosteroid injection for rotator cuff disease/impingement may be beneficial although the effect may be small and not well-maintained over time, when it seems to be no more beneficial than a comprehensive exercise and manual physical therapy program.

1.J. C. Winters, J. S. Sobel, K. H. Groenier, H. J. Arendzen, and B. Meyboom-de Jong. Comparison of physiotherapy, manipulation, and corticosteroid injection for treating shoulder complaints in general practice: randomised, single blind study. Brit Med Jour. 1997 May 3; 314(7090): 1320–1325.

2. Crawshaw DP, Helliwell PS, Hensor EM, Hay EM, Aldous SJ, Conaghan Exercise therapy after corticosteroid injection for moderate to severe shoulder pain: large pragmatic randomised trial.  BMJ. 2010 Jun 28;340:c3037

Q: What should PT consist of?

For patients and providers that are not familiar with the physical therapy experience, you should know:  Orthopedic physical therapists deal with disorders and injuries of the musculoskeletal system.  In the event of subacromial impingement syndrome (please see anatomy and cause in another post), the treatment should be multimodal in its approach, meaning the session should be balanced with the many interventions of physical therapy.  Physical therapists are known for their pursuit of being a profession based on evidence.  If a particular experience does not seem to represent that notion, a patient may want to explore other options (clinics/therapists).

Some of the evidence has shown that:
1. Scapular stabilization exercises can be an important component to the recovery as it more effectively increases strength, improves joint position sense, and reduces scapular dyskynesia.  Of course, there are a lot of exercises that can be effective and important in therapy, but this just shows that sometimes therapists need to think outside the localized area of pain to strengthen something further up the chain, like the base of the shoulder... the shoulderblade (which has 17 muscles attached to it!).  Example stabilization exercises include seated push-ups, high row, low rows, and scapular retraction with a theraband.

Another crucial part of your treatment can be assessed by how much time your therapist is spending with you.  If you are one of many patients during the therapist's hour of working, then you could probably be receiving better care somewhere else.  Furthermore, if the therapist does not have his/her hands on you, then the plan of care could be more productive somewhere else for the patient.  2.  Manual therapy can produce quicker results, such as increased strength, decreased pain, and improved function.  Manual therapy includes soft tissue mobilization, stretching the joint capsule, mobilizing the shoulderblade/thoracic joint, clavicle, etc. since all of these components help the shoulder to move.


Proceed with caution if you ask a therapist about what areas of his practice are evidence-based and he does not have a good answer.  Although modalities are not as well represented as manual therapy and exercise in physical therapy, there are still good studies that are performed on this subject.  Outside of the very popular electrical stimulation and ultrasound, taping techniques should also be considered 3. since they have been discovered to be a promising modality for decreasing pain and improving function.

The beauty of physical therapy is that there are many tools in the toolbelt.  So, if your therapist is not educating the patients or performing dynamic and diverse treatments with the patient, he/she may want to ask the therapist some questions about the plan of care and if there are any upcoming changes soon.  We don't always have to use all of the tools we have; but unlike many in the healthcare profession, physical therapists have more time with the patient, so they can use quite a few of them.


1.  The effectiveness of scapular stabilization exercise in the patients with subacromial impingement syndrome.

Başkurt Z, Başkurt F, Gelecek N, H Özkan M.

2.Comparison of conservative treatment with and without manual physical therapy for patients with shoulder impingement syndrome: a prospective, randomized clinical trial.

Senbursa G, Baltaci G, Atay A.

3. Taping patients with clinical signs of subacromial impingement syndrome: the design of a randomized controlled trial.

Kalter J, Apeldoorn AT, Ostelo RW, Henschke N, Knol DL, van Tulder MW.

Q: Can't I just do exercises on my own?

A: Patients with subacromial impingement syndrome that perform exercise only (specific prescribed exercise) or the same exercises plus manual therapy with a physical therapist may both experience significant decreases in pain and improvements in function.  However, these improvements may be significantly MORE for those that receive manual therapy.  Also, those that receive manual physical therapy may exhibit greater strength gains than those that do not. (1)

Another study (2) compared a group who performed active range of motion, stretching and strengthening exercise program including rotator cuff muscles and scapular muscles with an elastic band at home at least seven times a week for 10-15 min (group 1) with a group that received 12 sessions of joint and soft tissue mobilization techniques, an exercise program, and patient education in clinic for three times per week.  Subjects in both groups experienced significant decreases in pain and increases in shoulder function and range of motion, but there was significantly more improvement in the manual therapy group compared to the exercise group. (2)

Kachingwe et al (3) compared groups of patients receiving exercise only, exercise with specific manual therapy techniques, or advice only.  The groups receiving manual therapy demonstrated the best decrease in pain.  The three groups receiving intervention showed the best improvement in function. This pilot study suggests that with a therapist performing glenohumeral mobilizations and mobilization with movement in combination with a supervised exercise program, a greater decrease in pain and improved function may be seen.

1. Bang MD, Deyle GD.Comparison of supervised exercise with and without manual physical therapy for patients with shoulder impingement syndrome. J Orthop Sports Phys Ther. 2000 Mar;30(3):126-37.
2. Senbursa G, Baltaci G, Atay A.Comparison of conservative treatment with and without manual physical therapy for patients with shoulder impingement syndrome: a prospective, randomized clinical trial.  Knee Surg Sports Traumatol Arthrosc. 2007 Jul;15(7):915-21.
3. Kachingwe AF, Phillips B, Sletten E, Plunkett SW.  Comparison of manual therapy techniques with therapeutic exercise in the treatment of shoulder impingement: a randomized controlled pilot clinical trial.  J Man Manip Ther. 2008;16(4):238-47.