47year-old patient presenting with superior shoulder pain following trauma on a waterslide. Pain is localized over the acromioclavicular (AC) joint and is reproducible on palpation. Functional complaints include discomfort during shoulder movement (including exercise) and possible instability sensation.
Ultrasound examination of the right shoulder was performed according to the ESSR shoulder protocol, including additional assessment of the coracoclavicular ligaments and the rotator interval (including the superior glenohumeral ligament and coracohumeral ligament).
At the level of the AC joint, there are clear signs of injury, including cortical irregularity of the distal clavicle suggestive of erosion or post-traumatic change.
Dynamic ultrasound assessment during active, guided movement demonstrates instability of the AC joint, confirming functional impairment.
Palpation directly over the AC joint reproduces the patient’s pain, supporting this structure as the primary pain generator.
The coracoclavicular (CC) ligaments appear intact on ultrasound, and there is no significant superior displacement of the clavicle. These findings are most consistent with a Rockwood type II AC joint injury.
A higher-grade injury (Rockwood type III) cannot be entirely excluded based on ultrasound alone, as detailed evaluation of the CC ligaments may require MRI for higher diagnostic accuracy.
1. Final diagnosis
Findings consistent with a Rockwood type II acromioclavicular joint injury, with cortical irregularity and dynamic instability, and intact coracoclavicular ligaments.
2. Differential diagnosis
Consider Rockwood type III injury if subtle coracoclavicular ligament injury is present but not fully visualized. MRI may be considered for further assessment.
3. Teaching points
Dynamic ultrasound is valuable in assessing functional instability of the AC joint. Intact coracoclavicular ligaments do not exclude clinically relevant instability. Clinical correlation, particularly pain on palpation, is essential in identifying the AC joint as the pain source.
4. Injury/disease information
AC joint injuries are commonly classified using the Rockwood system. Type II injuries involve disruption of the AC ligaments with intact CC ligaments. While often managed conservatively, a subset of patients may develop chronic symptomatic instability requiring further intervention.
5. Management:
Initial management is conservative, focusing on structured rehabilitation including scapular stabilization and load management for at least 3 months.
A US-guided intra-articular AC joint injection may be considered to reduce pain and facilitate rehabilitation.
In cases of persistent symptoms (pain >3–6 months, functional limitations, or instability), chronic symptomatic AC instability should be considered. Referral to orthopedics may be warranted for evaluation of surgical stabilization, typically involving coracoclavicular reconstruction, with or without AC capsular reconstruction.
6. Note:
Structurally intact coracoclavicular ligaments do not exclude functional instability. Treatment decisions should be guided primarily by clinical symptoms and functional limitations.
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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