Acromioclavicular Joint Bursa

bursa articulationis acromioclavicularis

A small bursa is sometimes present superior to the acromioclavicular joint capsule, between the distal clavicle and the overlying deltotrapezius fascia. It is more consistently present in patients with AC joint arthrosis or post-traumatic degenerative change, where the osteophytes and capsular hypertrophy cause friction between the joint complex and the overlying structures. It is distinct from the subacromial bursa below.

Region: Shoulder

Clinical Relevance

Clinical Notes

AC joint bursitis, distinct from subacromial bursitis, produces a discrete localised swelling and tenderness directly over the AC joint that is reproduced by horizontal adduction and direct vertical joint compression. Ultrasound demonstrates a fluid collection between the AC joint capsule and the deltotrapezius fascia. Corticosteroid injection specifically targeting the AC joint (with separate injection above the joint capsule for bursitis) provides more durable relief than combined injection. Os acromiale, where the acromion fails to fuse, creates a pseudarthrosis at the AC level with associated bursitis.

Pathology

Common Injuries & Conditions

AC Joint Bursitis and Arthrosis

Degenerative AC joint arthrosis produces both intra-articular synovitis and a superior bursal reaction, causing a characteristic point tenderness at the AC joint reproduced by horizontal adduction, managed with corticosteroid injection and, for refractory arthrosis, arthroscopic distal clavicle excision.