What are the key clinical features to differentiate frozen shoulder from other shoulder pathologies?

The key clinical features used to differentiate frozen shoulder (adhesive capsulitis) from other shoulder pathologies primarily revolve around the characteristic progression of symptoms and specific limitations in joint movement NICE CKS.

• Frozen Shoulder Features: Initially, pain is the main problem, often worsening in bed and disturbing sleep NICE CKS. This pain gradually improves, but stiffness slowly worsens and becomes the primary issue NICE CKS. The stiffness then gradually resolves, with the condition typically being self-limiting, though resolution can take months to years NICE CKS. A crucial diagnostic feature is reduced passive external rotation, which indicates a glenohumeral joint disorder, encompassing both frozen shoulder and arthritis NICE CKS.
• Differentiating from Other Pathologies:
  • Red Flags: Urgent referral to secondary care is necessary if certain red flags are identified, which are not typical of frozen shoulder NICE CKS. These include trauma, pain with weakness, or sudden loss of active arm raising (suggesting an acute rotator cuff tear) NICE CKS. Any shoulder mass or swelling should raise suspicion of malignancy NICE CKS, (Demazière & Wiley 1991). Red skin, a painful joint, fever, or systemic unwellness may indicate septic arthritis NICE CKS. Trauma leading to loss of rotation and an abnormal shape suggests a shoulder dislocation NICE CKS. New symptoms of inflammation in several joints point towards inflammatory arthritis NICE CKS.
  • Rotator Cuff Disorders: These are likely if there is a painful arc of abduction or pain on abduction with the thumb down NICE CKS. An acute rotator cuff tear, especially in a young person with trauma and loss of abduction, requires urgent referral NICE CKS. Unlike frozen shoulder, rotator cuff issues often involve specific active movement limitations rather than global passive stiffness NICE CKS.
  • Shoulder Instability: A diagnosis of instability is likely if there is a history of the shoulder coming out of joint or if the person is concerned about dislocation during certain activities or sports NICE CKS.
  • Acromioclavicular (AC) Joint Disease: This is likely with pain and tenderness over the AC joint, high arc pain, or a positive cross-arm test NICE CKS.
  • Glenohumeral Osteoarthritis: While also presenting with reduced passive external rotation, osteoarthritis is characterized by joint symptoms such as pain, stiffness, reduced function, or progressive joint deformity that significantly impact quality of life NICE CKS,NICE NG226. Atypical features for osteoarthritis, which would differentiate it from typical frozen shoulder, include a history of recent trauma, prolonged morning joint-related stiffness, rapid worsening of symptoms or deformity, the presence of a hot swollen joint, or concerns suggesting infection or malignancy NICE NG226. Imaging is not routinely used for follow-up or to guide non-surgical management of osteoarthritis NICE NG226.