Subacromial Pain Syndrome

Subacromial pain syndrome (SAPS) is shoulder pain arising from the structures between the coracoacromial arch and the rotator cuff, mainly rotator cuff tendinopathy and subacromial bursitis.

It has replaced 'impingement' as the UK term, because the mechanical model of the acromion abrading the tendon is not well supported. Rotator cuff related shoulder pain (RCRSP) is a wider umbrella that also takes in partial and full-thickness cuff tears. SAPS is most common in adults aged 40 to 60 and in people doing sustained overhead work.

The subacromial space lies between the coracoacromial arch above and the rotator cuff below. The subacromial-subdeltoid bursa sits in this space and reduces friction between the cuff (mainly supraspinatus) and the acromion and deltoid. It does not normally communicate with the glenohumeral joint.

SAPS is now understood as a degenerative and reactive process of the cuff and bursa rather than simple mechanical impingement. Bursitis is usually secondary to cuff tendinopathy, a partial cuff tear or calcific tendinopathy. Less common causes include haemorrhagic bursitis after trauma, crystal deposition (gout, pseudogout) and, rarely, septic bursitis, usually Staphylococcus aureus in people with diabetes or immunosuppression.

Risk factors include age 40 to 60, repetitive overhead activity, diabetes and rheumatoid arthritis. Metabolic syndrome has a low to moderate evidence association, and psychosocial factors can affect symptoms and outcome.