1. There’s no substitute for knowing the anatomy when examining the shoulder. Ideally, this means a good picture of the major structures: the shoulder capsule, the AC (acromioclavicular) joint, the subacromial bursa and the rotator cuff tendons. Know which rotator cuff tendons govern which movements: supraspinatus for abduction, infraspinatus and teres minor for external rotation, subscapularis for internal rotation. With this knowledge, a good history will get you a long way.
2. That doesn’t mean you can routinely make diagnoses by asking the patient exactly where the pain is. Shoulder pain is often referred from elsewhere, including the neck, gallbladder and lung apex (i.e. Pancoast tumour). Polymyalgia rheumatica also causes shoulder pain. Check ESR and CRP if you find no proximal cause.
3. You can make educated guesses based on the range of movement. Don’t forget neck flexion (including lateral), rotation and neck extension.
4. When the pain is above the clavicle, suspect the neck or the AC joint. Injured AC joints are often tender on palpation. There’s liable to be pain on resisted adduction. Standing at the patient’s side with their arm hanging straight down, try to lift it towards you and tell them to resist the pull. Pain suggests AC joint injury. Test the other side for comparison if you need to.
5. In tendon injury, some weakness or pain implies a partial tear or tendonitis — a completely torn tendon exhibits complete weakness and no pain.
6. There are four broad categories of shoulder problem: rotator cuff problems; impingement problems, usually where the supraspinatus gets trapped under the acromium during movement; capsulitis, which tends to restrict all movement; and arthritis.
7. Rotator cuff problems can generally be traced to trauma, but it may be very minor trauma in the elderly. A complete tear will leave the patient unable to support the arm at 90o. Lesser tears will cause specific muscle signs. Test infraspinatus with elbow at side, bent 90o, ask patient to rotate forearm outward against your resistance, looking for pain. See http://mmiweb.mmi.mcgill.ca/dev/shoulder/exam.htm for a fuller guide to testing rotator cuff tendons. US can confirm tears. Treatment ranges from conservative physiotherapy to arthroscopic surgery.
8. Impingement generally causes pain through the middle part of the arc of abduction. The first 50o are painless, the next 40o hurts (while the supraspinatus is under the acromium), and the end of the abduction motion is again pain-free. Pain upon reaching above the head may signal either impingement or rotator cuff problem. Use the Hawkins-Kennedy test: upper arm forward, elbow bent 90o, forearm across chest; push wrist down gently, looking for pain along top of shoulder. Treatment is typically steroid injection and physiotherapy. Impingement can tear the supraspinatus, especially if there are osteophytes on the acromium.
9. Capsulitis is fibrosis of the joint capsule, particularly associated with diabetes, and most common in middle-aged women. Onset is insidious, beginning with pain, including night pain, often severe. This can last for months, accompanied by stiffness, which can last years. Movement restriction is the defining trait, individual muscle tests rarely show weakness. Full external rotation basically excludes adhesive capsulitis (frozen shoulder). Treatment is typically steroid injection and physiotherapy.
10. Arthritis will reveal itself through pain and limitation in passive elevation, abduction, internal and external rotation. Joint replacement is the gold standard. Plain x-ray can confirm joint erosion.