Shoulder
Piano key sign
- What you examine
- Vertical instability of the acromioclavicular joint after a dislocation.
- Procedure
- Push the lateral end of the clavicle down with one finger and release.
- Positive when
- The clavicle springs back up like a piano key as soon as you release.
- What the test is worth
- High specificity for a grade III or higher AC dislocation. In grades I and II the sign is absent.
- Caution
- The prominence is the clavicle staying up, not the acromion dropping: the arm sinks down with the scapula.
- Body region
- Shoulder