47-year-old patient with right shoulder symptoms. Ultrasound examination was performed according to the full ESSR shoulder protocol, with additional assessment of the rotator interval, including the superior glenohumeral ligament and coracohumeral ligament.
Ultrasound examination of the right shoulder demonstrates widening of the acromioclavicular joint, compatible with mild AC joint diastasis. The appearance is consistent with a low-grade AC joint injury, corresponding to Rockwood grade I. There is associated moderate synovitis of the AC joint with swelling and thickening of the joint capsule.
There are also findings consistent with subacromial pain syndrome. The supraspinatus tendon shows moderate tendinopathy in the dysrepair phase. Within the supraspinatus tendon, a longitudinal intratendinous calcification is visible between the tendon fibers, measuring approximately 7.7 × 4.3 mm.
There is mild swelling of the glenohumeral capsule, visible as a mildly enlarged posterior glenohumeral recess. Within the glenohumeral joint, a dynamically changing hyperechoic structure is seen during active external rotation. Based on its appearance and variability during movement, this most likely represents an air bubble or swirling debris within joint fluid, rather than a fixed intra-articular structure.
Ultrasound has limited reliability for further assessment of intra-articular glenohumeral pathology, including labral, chondral, osseous, and deeper capsuloligamentous abnormalities.
Conclusion
1. Final diagnosis
Findings are consistent with mild right AC joint diastasis, compatible with Rockwood grade I, with moderate AC joint synovitis and capsular swelling. There is associated subacromial pain syndrome due to moderate supraspinatus tendinopathy in the dysrepair phase, with a longitudinal intratendinous calcification measuring approximately 7.7 × 4.3 mm. Mild glenohumeral joint swelling is also present, with a dynamic hyperechoic intra-articular finding most likely representing an air bubble or fluid swirling/debris.
2. Differential diagnosis
The primary differential diagnosis includes combined AC joint pathology and subacromial pain syndrome. The AC joint findings may be post-traumatic or related to mechanical overload. The supraspinatus findings are compatible with degenerative tendinopathy with a calcific component. The glenohumeral swelling may be reactive, but intra-articular pathology such as labral injury, chondral injury, capsulitis or synovitis, post-traumatic irritation, or a loose body should be considered. A fixed intra-articular structure is less likely because of the dynamically changing appearance, but cannot be reliably excluded by ultrasound.
3. Teaching points
When multiple shoulder abnormalities are present, each potential pain generator should be correlated separately with the clinical examination. AC joint synovitis, supraspinatus tendinopathy with calcification, and glenohumeral joint swelling may each contribute differently to symptoms. Dynamic ultrasound can help characterize mobile echogenic intra-articular findings, but ultrasound remains limited for assessing labrum, cartilage, bone marrow, and deeper intra-articular structures.
4. Injury/disease information
Low-grade AC joint diastasis may occur after trauma or repetitive mechanical overload and can cause focal superior shoulder pain, pain with cross-body adduction, and local capsular swelling. Supraspinatus tendinopathy with intratendinous calcification can contribute to subacromial pain, especially during elevation or loaded shoulder activity. Glenohumeral joint swelling indicates an intra-articular reaction; if symptoms include locking, deep joint pain, persistent motion restriction, post-traumatic progression, or inadequate recovery with conservative care, MRI is better suited to assess labral, chondral, osseous, and other intra-articular pathology.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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