Subacromial Impingement Syndrome – A Brief Overview
by Steve Young BHSc, PT, tDPT(c)
Shoulder pain is one of the more common conditions that physiotherapists treat in an
orthopaedic setting, with many patients describing impingement-like symptoms.
Subacromial impingement syndrome (SAIS) is defined as mechanical compression of
structures in the subacromial space with movements above shoulder height. Neer (1)
originally proposed the idea of impingement syndrome and attributed its development to
an unfortunate acromial shape: the infamous hooked acromion. We now know that SAIS
has a multitude of potential causes that include local factors (acromial shape and/or
rotator cuff weakness) as well as regional factors (scapula dyskinesis, regional
hypomobility and/or multidirectional instability). To the benefit of the clinician SAIS has
been categorized into Primary SAIS and Secondary SAIS. Primary refers to
glenohumeral impingement secondary to a mechanical block, and secondary refers to
impingement occurring due to instability as a result of excessive mobility or a loss of
motor control. Typically, SAIS is diagnosed based on a history, with patients describing
pain with overhead movements, shoulder stiffness and pain at night. As with most
conditions, clinical tests simply serve to confirm the diagnosis based on the history.
For many years, the Neers and Hawkins-Kennedy tests were considered the best tests for
SAIS. Both tests demonstrate good sensitivity, suggesting that a negative test helps rule
out a SAIS (2). Unfortunately, a positive Neers or Hawkins-Kennedy test in isolation
does little to improve our confidence in a diagnosis of SAIS. In recent years, clinical tests
for SAIS have been clustered to improve their diagnostic accuracy.
Park et al. (3) retrospectively looked at patients presenting for surgery and compared their
outcomes with presurgical screening test. They used the painful arc, infraspinatus muscle
strength test and Hawkins-Kennedy tests to identify SAIS. If two of the three screening
tests for SAIS were positive, this was associated with impingement findings upon
surgical visualization. Park et al. also found that by replacing the Hawkins-Kennedy test
with the drop arm test, the three tests became diagnostic for a full thickness tear of the
rotator cuff. Michener et al. (4) performed a similar study prospectively and found that a
cluster of five tests was beneficial in diagnosing shoulder impingement syndrome. They
included the Hawkins-Kennedy sign, painful arc and resisted external rotation tests as
cited by Park et al. They also included the empty can test and Neer’s sign for
impingement, with three or more tests improving the likelihood of diagnosing SAIS.
With patients presenting with secondary impingement, the above noted tests may be
positive but there will be other findings such as glenuhumeral ligament laxity or an
altered scapulohumeral rhythm observed with movements.
Park et al. SAIS tests



Painful arc
Infraspinatus muscle
strength test
Hawkins-Kennedy
sign
Park et al. full thickness tear Michener et al. SAIS tests
tests
 Positive drop arm
 Painful arc
test
 Infraspinatus muscle
 Infraspinatus muscle
strength test
strength test
 Painful arc
 Hawkins-Kennedy
 Neer’s test
sign
 Empty can
Once a diagnosis of SAIS has been established, here is the great news: our multimodal
physiotherapy treatment has equal outcomes to cortisone injection and subacromial
decompression in two recently published papers. Rhon et al. (5) compared the efficacy of
cortisone injections to physical therapy for SAIS. One hundred and four patients were
randomized to either receive cortisone injection or physical therapy. The physical therapy
treatment consisted of cervicothoracic and shoulder girdle manual therapy and exercise as
determined by the treating physiotherapist based on each patient’s impairment findings.
Both groups demonstrated a 50% improvement in functional outcomes at a one year
follow-up. Although there were no differences in outcomes between the two groups at
any point during the trial, those receiving physical therapy had fewer future visits to
physicians and fewer repeat cortisone injections. No significant adverse effects were seen
in either group, although a previous study with SAIS patients did identify a risk of
progression of rotator cuff tears from partial thickness to full thickness in patients
receiving cortisone injection (6). In a recent systematic review of the literature (7), four
studies compared conservative management with surgical intervention for SAIS. None of
the studies reviewed were of strong methodological quality but they all identified no
advantage of surgical intervention over conservative management, with surgery carrying
significant potential risk for the patient. It is noteworthy that one trial compared
supervised exercise with surgical subacromial decompression for SAIS and found no
differences in outcomes between the two treatments (8). Recent research has
demonstrated a clear advantage of combining exercise with manual therapy over exercise
alone for the treatment of SAIS (8); it would be interesting to see a trial comparing
combined manual therapy and exercise with surgical intervention for SAIS.
Based on the research, physiotherapy should be an obvious first line intervention for
SAIS.
1. Neer, Charles S. "Impingement lesions." Clinical orthopaedics and related research 173
(1983): 70-77.
2. Hegedus, Eric J., et al. "Which physical examination tests provide clinicians with the
most value when examining the shoulder? Update of a systematic review with metaanalysis of individual tests." British Journal of Sports Medicine (2012): bjsports-2012.
3. Park, Hyung Bin, et al. "Diagnostic accuracy of clinical tests for the different degrees
of subacromial impingement syndrome." The Journal of Bone & Joint Surgery 87.7
(2005): 1446-1455.
4. Michener, Lori A., et al. "Reliability and diagnostic accuracy of 5 physical
examination tests and combination of tests for subacromial impingement." Archives of
Physical Medicine and Rehabilitation 90.11 (2009): 1898-1903.
5. Rhon, Daniel I., Robert B. Boyles, and Joshua A. Cleland. "One-Year Outcome of
Subacromial Corticosteroid Injection Compared With Manual Physical Therapy for the
Management of the Unilateral Shoulder Impingement Syndrome: A Pragmatic
Randomized Trial." Annals of Internal Medicine 161.3 (2014): 161-169.
6. Ramírez, Julio, et al. "Incidence of full-thickness rotator cuff tear after subacromial
corticosteroid injection: A 12-week prospective study." Modern Rheumatology 0 (2013):
1-4.
7. Dorrestijn, Oscar, et al. "Conservative or surgical treatment for subacromial
impingement syndrome? A systematic review." Journal of Shoulder and Elbow Surgery
18.4 (2009): 652-660.
8. Brox, Jens Ivar, et al. "Arthroscopic surgery versus supervised exercises in patients
with rotator cuff disease (stage II impingement syndrome): a prospective, randomized,
controlled study in 125 patients with a 2-1/2-year follow-up." Journal of shoulder and
elbow surgery 8.2 (1999): 102-111.
9. Bang, Michael D., and Gail D. Deyle. "Comparison of supervised exercise with and
without manual physical therapy for patients with shoulder impingement syndrome."
Journal of Orthopaedic & Sports Physical Therapy 30.3 (2000): 126-137.