Shoulder pain can be difficult to assess as symptoms and signs often overlap and frequently evolve over time. To assist us in diagnosing shoulder pain, we generally try to group symptoms and signs into patterns.
First of all, consider the demographic of your patient. Are they middle-aged, diabetic and not particularly active - in which case a capsulitis might be more common – or a tradie who hits the gym, in which case rotator cuff/impingement or AC joint problems would be more likely?
Consider also the history. Has there been a genuine acute injury or a more gradual onset of pain? Remember that what seems like a low energy injury (such as reaching into the back seat of the car, or having the dog pull on its lead) can actually be the initial manifestation of pain in a capsulitis.
The site of pain can be a clue. Glenohumeral pain is often felt in the upper arm and may radiate in a non-dermatomal fashion down toward the hand. AC joint pain is typically felt through the top of the shoulder. A cervical nerve root may radiate pain into the medial scapular region.
With regard to examination, consider the following patterns:
Bear in mind some signs will overlap. Impingement tests are often painful in a capsulitis, while cuff testing (and especially reaching behind the back) is often provocative of AC joint pain.
Radiology is an area which is frequently misunderstood. Bursitis is over diagnosed, as evidenced by the large number of people who receive an ultrasound-guided injection into the bursa, without any improvement in their pain whatsoever. Bursal thickening is common in overhead athletes and workers, and in many cases can be considered analogous to the thickening of the skin on the palms that occurs with habitual weight training. A bursal effusion can be seen in capsulitis. While a bursa may be seen to “impinge” on an ultrasound, this doesn’t necessarily mean it is the cause of pain.
Similarly, rotator cuff changes are common with advancing years, and it can be challenging to work out exactly what is symptomatic. The importance of a good history and examination cannot be overstated with regard to the interpretation of radiological findings.
Bear in mind that the patient only gets one ACC-funded injection per claim without needing further approval. Many patients have their “free” injection given into the bursa, only to have difficulty accessing a glenohumeral injection when their “bursitis” turns out to be capsular pain.
Plain x-rays are often overlooked but do play an important role in exploring the differential diagnosis in shoulder pain.
In summary, shoulder pain can seem difficult to pin down, and it is common to feel as if you are chasing your tail diagnostically. Observing how the patient evolves over time and observing clinical patterns in the manner described above can be helpful.