Shoulder pain referred from cardiac or abdominal sources accounts for a significant proportion of missed diagnoses in primary care. Shoulder-tip pain may be referred from the diaphragm, pleura, gallbladder, liver, pericardium or other structures (e.g. sub-diaphragmatic haemorrhage, abscess, ectopic pregnancy) — interpret it in clinical context rather than as a specific "phrenic nerve" sign. Pancoast tumours are particularly important — they arise at the lung apex, can be hard to see on a standard CXR (a normal film does not exclude one if suspicion persists), and cause a characteristic triad of arm pain, Horner's syndrome, and hand weakness. NICE NG12 does not list shoulder pain itself as a criterion; the lung triggers are an urgent chest X-ray (within 2 weeks) for people aged 40 and over with the specified unexplained symptoms (e.g. weight loss in someone who has ever smoked), and a suspected cancer pathway referral if the X-ray suggests lung cancer or with unexplained haemoptysis at 40 and over. Septic arthritis of the glenohumeral joint carries significant morbidity and mortality and must be aspirated urgently.

The movement restriction pattern is a useful, but not absolute, diagnostic discriminator. True frozen shoulder (adhesive capsulitis) causes global restriction of both active AND passive movements — passive external rotation is the first and most severely restricted. In rotator cuff tears, passive movement is relatively preserved but active is restricted — as also seen with pain inhibition or neurological disease. A painful arc supports rotator-cuff-related shoulder pain but does not identify a single anatomical lesion. Diabetes is the strongest risk factor for frozen shoulder. Night pain is important — it should prompt active consideration of malignancy and RC tear, with imaging where it will change management.

Accurate classification prevents inappropriate treatment and imaging. Rotator-cuff-related shoulder pain is the most common diagnosis but "impingement" is frequently over-diagnosed — cervical referred pain is commonly mistaken for shoulder pathology. The key differentiator is passive shoulder range: if passive movement is full and painless, the glenohumeral joint itself is unlikely to be the source. Frozen shoulder is frequently misdiagnosed and overtreated with cortisone without physiotherapy — the condition often improves but has a variable natural history, and treatment decisions should account for this. For suspected cuff tear, ultrasound or MRI may be appropriate depending on local expertise, availability and the clinical question — ultrasound is operator-dependent; do not routinely request both. ACJ pathology is identified by the scarf test and point tenderness at the joint line, not generalized shoulder pain.

The passive vs active range distinction is a key, though not absolute, examination finding for shoulder diagnosis. Neck examination is non-negotiable — cervical radiculopathy is a common mimic of shoulder pain. The drop arm sign (inability to slowly lower the arm from 90° abduction) has high specificity for full-thickness supraspinatus tear. Hawkins–Kennedy and Neer tests have poor specificity — use them as part of a test cluster rather than as proof of impingement. Infraspinatus wasting in the posterior shoulder fossa is highly significant and indicates either RC tear or suprascapular nerve entrapment — do not miss this. Axillary nerve function must be assessed after every shoulder dislocation before and after reduction.

Over-investigation of shoulder pain is a major NHS resource issue — most rotator-cuff-related pain presentations require no imaging and should proceed directly to physiotherapy. Frozen shoulder is diagnosed clinically, but the BESS/BOA pathway advises plain radiographs in two planes to exclude glenohumeral arthritis, avascular necrosis or dislocation before confirming the diagnosis or referring; image sooner after trauma or with atypical features. However, ultrasound is appropriate and cost-effective when a rotator cuff tear is clinically suspected (weak empty can, drop arm sign, age >60 with acute-on-chronic pain). Ultrasound has excellent specificity for full-thickness tears. MRI is more sensitive for partial tears but should generally be requested by orthopaedics when surgical planning is needed. CXR is the first test when Pancoast tumour is in the differential — apical lesions can be missed on a plain film, so persisting suspicion warrants discussion with the respiratory team despite a normal CXR. Raised ESR/CRP supports PMR, and a dramatic response to corticosteroid supports but does not prove the diagnosis — mimics must be excluded.

The vast majority of shoulder pain is safely managed in primary care — rotator-cuff-related pain, mild RC tendinopathy, and frozen shoulder should all receive a trial of physiotherapy before referral. However, an acute traumatic cuff tear needs urgent referral, ideally to the next available specialist shoulder clinic (BESS/BOA), because early repair gives better results before tendon retraction and fatty infiltration; atraumatic degenerative tears are referred routinely if not improving with rehabilitation. PMR is commonly started on prednisolone 15 mg daily in primary care after clinical assessment (BSR/BHPR 2009; EULAR/ACR 2015 range 12.5–25 mg) — a dramatic response supports but does not prove the diagnosis, so exclude mimics, assess for GCA, and review response and steroid toxicity. Recurrent dislocation requires Bankart repair assessment — each dislocation risks further labral damage and Hill-Sachs lesion enlargement, increasing instability.

Subacromial corticosteroid injection gives short-term pain relief for subacromial pain, but the effect is not durable (weeks) without physiotherapy. Trials suggest exercise therapy and injection have similar outcomes by 12 months — injections are adjuncts that facilitate engagement with rehabilitation. Topical NSAIDs are recommended first-line for localised musculoskeletal pain before systemic NSAIDs (lower GI/renal/CV risk). Hydrodilatation (high-volume arthrographic distension) is a secondary-care option for frozen shoulder that is not settling, alongside MUA and capsular release (BESS frozen shoulder pathway 2025). Prednisolone for PMR should be started without undue delay once clinically assessed and mimics considered — the ESR/CRP are supportive but not diagnostic, and treatment should not be withheld pending rheumatology in a patient with typical features.

The CSAW trial (Beard et al., Lancet 2018) randomised patients to arthroscopic subacromial decompression, investigational arthroscopy only (placebo) or no treatment: decompression gave no extra benefit over arthroscopy only, and neither surgical group differed from no treatment by a clinically important amount. A BMJ Rapid Recommendation (2019) makes a strong recommendation against decompression for subacromial pain, so conservative care centred on exercise is the default. Ergonomic advice should be practical and based on symptoms and work demands, without implying that a particular posture prevents structural damage. Sleep disruption from shoulder pain is a significant contributor to quality of life impairment and should be addressed — simple positional advice (pillow support) may help. Glycaemic control in diabetes is one of the few modifiable risk factors for frozen shoulder and is an important co-management target.

Review timing should reflect severity, diagnosis and response — persistent symptoms despite an appropriate rehabilitation programme should prompt diagnostic re-evaluation and consideration of imaging, not just another injection. Injection without physiotherapy has poor long-term outcomes — the exercise programme must be reinforced at every review. PMR relapse is common during steroid taper and presents as return of bilateral girdle stiffness and rising ESR/CRP — patients should know to return if this happens. Safety-netting for GCA is particularly important in PMR patients — a minority of people with PMR develop GCA. Visual symptoms in a PMR patient are a same-day emergency (start glucocorticoids promptly per the local fast-track GCA pathway and arrange same-day specialist/ophthalmology assessment). Failure to improve after adequate conservative management should always prompt re-evaluation for missed diagnosis, particularly malignancy.