51-year-old patient presenting with chronic superior shoulder pain localized to the acromioclavicular (AC) joint. Symptoms are persistent despite conservative management, with stagnation in rehabilitation progress. Palpation over the AC joint reproduces the patient’s pain.
Ultrasound examination of the AC joint demonstrates features consistent with synovitis, including joint distension and synovial thickening.
The joint width appears to be widened
There is cortical irregularity of the distal clavicle, suggestive of erosive or degenerative changes.
Dynamic ultrasound assessment during active, guided movement demonstrates instability at the AC joint, with abnormal joint motion compared to expected biomechanics.
Direct palpation over the AC joint is clearly painful and correlates well with the imaging findings, supporting the AC joint as a potential pain generator.
Given the chronicity of symptoms and limited response to conservative therapy, further diagnostic clarification is clinically relevant.
1. Final diagnosis
AC joint synovitis with cortical irregularity (erosion) of the distal clavicle and dynamic instability, likely contributing to chronic shoulder pain.
2. Differential diagnosis
Consider degenerative AC joint osteoarthritis, post-traumatic AC joint instability, or inflammatory arthropathy. Clinical and possibly laboratory correlation may be required.
3. Teaching points
Ultrasound can effectively demonstrate AC joint synovitis, cortical changes, and dynamic instability. Correlation with focal tenderness strengthens diagnostic confidence. In cases of persistent symptoms, diagnostic injections can help confirm the pain source.
4. Injury/disease information
AC joint pathology is a common source of superior shoulder pain. Chronic overload, degeneration, or prior trauma can lead to synovitis, instability, and cortical changes. When conservative management fails, targeted interventions may be considered.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at the Laurentius Hospital in Roermond, the Netherlands.
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