Painful arc and impingement syndrome ?
Impingement syndrome ? Is it a diagnosis?
No , it isn't, it just means that, during e.g. arm elevation, pain is provoked, usually between 80° and 110°, due to compression of a sensitive or inflammed structure between the tuberosities and the acromion. Clinically we often see a painful arc on elevation.
What exactly is a painful arc ?
This is a painful passage which occurs during an active or passive movement, mostly midrange and always inbetween two painfree zones within the same movement. This is a very common sign in shoulder pathology, but we can also find it in relation to lumbar problems (e.g. a painful arc on Straight Leg Raise).
A painful arc must be regarded as an accessory sign. Once the tissue at fault is singled out, the arc shows which part of the structure is affected.
Impingement in the shoulder may be due to stenosis, inflammation and/or fibrosis of the content in the subacromial space.
Young athletes using the arm in an overhead position are at risk of impingement because of the repetitive microtrauma of the structures under the acromion.
Impingement may also be secondary to minor instability, possibly involving labral tears.
Impingement ? What is the clinical meaning of a painful arc in the shoulder ?
A painful arc is the result of a momentary impingement, the question however is : “Which structure is impinged ?”
Most common reasons of a painful arc during lateral elevation :
- Impingement of the tenoperiosteal aspect of the supraspinatus muscle ; in that case there will also be pain on resisted abduction
- Impingement of the tenoperiosteal aspect of the infraspinatus muscle ; in that case there will also be pain on resisted lateral rotation
- Impingement of the cranial tenoperiosteal aspect of the subscapularis muscle ; in that case there will also be pain on resisted medial rotation
- Impingement of the caudal part of the acromioclavicular joint
- Impingement of the subdeltoid bursa in case of a chronic subdeltoid bursitis (Cave : in an acute bursitis there is never a painful arc
A painful arc can also be found during passive medial rotation, pointing in the direction of a chronic subdeltoid bursitis.
In order to detect a painful arc we need to perform our tests in a good way : stop at the first pain, inform about the localisation and the quantity of the pain, but…then continue the testmovement and interpret whether or not we can provoke a painful arc.
- If we perform the lateral elevation in a normal way, we mainly compress supraspinatus.
- If we elevate and simultaneously build in lateral rotation (so, palm up), then we compress more subscapularis.
- If we build in more medial rotation, we compress more infraspinatus.
- If we do an anterior elevation + lateral rotation, we compress more the long head of biceps.
So, impingement syndrome is not a diagnosis, it is merely a statement, but more to the point examination is preferred in order to determine which structure is impinged. This will also allow a more specific treatment.
Keep one important message in mind : one single positive test has no clinical meaning at all ; focus on the complete image : history, inspection and a cluster of positive and negative tests.
For more detailed analysis and recent scientific background of the clinical images described above, I refer to the ETGOM training programs in Modern Orthopaedic Medicine Cyriax and to our publications.