Frozen shoulder is primarily a clinical diagnosis. The central task is to recognise a characteristic pattern of pain and restriction while remaining alert to other shoulder, neurological and systemic conditions that can look similar.
Progressive loss of both active and passive movement—especially external rotation—is the key clinical pattern. Plain radiographs are commonly used to exclude important alternatives. Ultrasound and MRI can support a difficult differential diagnosis, but are not routinely required to confirm an otherwise typical primary frozen shoulder.
What clinicians are trying to establish
A useful assessment answers three questions: does the presentation fit frozen shoulder; is there evidence of another or additional disorder; and how irritable is the condition now? The history should establish onset, symptom behaviour, sleep disturbance, functional loss, previous trauma or surgery, diabetes and thyroid history, neurological symptoms and systemic warning signs.
The movement pattern
Restriction of active movement alone is not enough. Pain, fear, weakness and rotator cuff disease may all limit what a patient can do actively. Frozen shoulder becomes more likely when passive movement is also restricted in a capsular pattern. External rotation with the arm by the side is usually particularly limited, although the exact pattern and magnitude vary.
Assessment should record movement in a repeatable way rather than force an acutely painful shoulder to an artificial end point. Comparing active and passive range, observing scapular compensation and documenting functional tasks can be more informative than relying on one angle.
Imaging: exclusion rather than confirmation
Current guidance treats imaging as an adjunct. Plain radiography can identify glenohumeral osteoarthritis, fracture, dislocation and some other structural causes of stiffness. Ultrasound may help when a substantial rotator cuff tear or calcific tendinopathy is suspected. MRI can show findings associated with adhesive capsulitis, but those findings are not sufficiently specific to replace clinical assessment.
Important differential considerations
- Glenohumeral osteoarthritis or inflammatory arthropathy
- Rotator cuff tear, calcific tendinopathy or severe subacromial pain
- Post-traumatic or post-operative stiffness
- Cervical radiculopathy, peripheral nerve disorder or neurological disease
- Infection, tumour or referred visceral pain
Urgent investigation or referral is appropriate when there is significant trauma, systemic illness, unexplained swelling, neurological deficit, suspected infection or malignancy, or a course that does not fit the expected presentation.
Implications for practice
Diagnosis should remain provisional enough to be reviewed. Record the working diagnosis, relevant exclusions, irritability, functional priorities and reasons for any imaging or referral. Reassessment matters when symptoms change or progress fails to match expectations.