The Art of the Painful Arc

Orthopedic tests don’t need to be complicated. While there is no absolutes, small shifts in post-test probability can make a big difference. When combined with a little logic, a simple observation can go a long way in your clinical decision making.

Active range of motion is a standard screen routinely performed for shoulder pain. A painful arc is determined when the patient experiences shoulder pain in a range of 60-120 degrees of shoulder abduction.

A meta-analysis performed by Hegedus in 2012 demonstrated that a painful arc was neither sensitive nor specific. So what now? If this test cannot rule in or rule out pathology then why should we care? “Success is in the details”. When you look at the fine print and crunch the numbers, a painful arc can shift the post test probability that the patient in front of you is 15% more likely to have a shoulder impingement/rotator cuff tendinopathy as the cause of their pain.

If your patient is 60 years old, they are already 25% more likely to have rotator cuff tendinopathy when they complain of shoulder pain. If that same patient demonstrates a painful arc they are now 40% more likely to have a rotator cuff tendinopathy present (25% + 15% = 40%). Why is this significant? Herein lies the value. This 40% shift in probability is given to us without any additional subjective or objective information about this patient!

Now let’s add some logic thanks to the work of James Cyriax and take the clinical application of a painful arc to another level. While not necessarily validated by clinical trials, we can apply some clinical anatomy to make this more interesting.

Clinical pearls & correlations to the supraspinatus tendon:

- A painful arc tells you that the lesion has to be located at a pinchable site, therefore it lies at the subacromial space. If the patient has a painful arc and experiences pain with resisted shoulder abduction, the problem lies at the supraspinatus tenoperiosteal junction and superficially (bursal side of the tendon).

* If a patient has a painful arc that is present with the palm facing up rather than facing down, the problem is located at the anterior portion of the supraspinatus tenoperiosteal junction (Large Intestine, Lung channel).

* If a patient has a painful arc that is present with the palm facing down rather than facing up, the problem is located at the posterior portion of the supraspinatus tenoperiosteal junction (Large Intestine, Triple Burner channel).

* If a patient does not have a painful arc but does have pain with resisted abduction and passive flexion or abduction end range, the problem is located at the supraspinatus tenoperiosteal junction but deep (articular side of the tendon).

* If the patient does not have a painful arc or pain with passive end range flexion/abduction but has pain with resisted abduction, the problem is more likely located at the supraspinatus musculotendinous junction (Large Intestine 16 region).

As you can see, if you only had one acupuncture needle your treatment approach can be very specific regardless of acupuncture style. If you needle locally, you will have a better understanding of exactly where to place needles. If you prefer distal needling, your mirror imaging and channel diagnosis can become that much more specific.

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