Contributor: Nick Hatch, MD Educational Pearls: An AC (acromioclavicular joint) separation in the shoulder is a common traumatic injury XRs can help rule out other injuries as well as help with grading the injury There are six different grades for AC separations: Grade I: is stretching of the AC ligament without disruption or displacement of the clavicle and recovers with time. Grade II:  is partial tearing of the AC ligament with some displacement but will also heal with time. Grade III: is a full separation with ligament rupture and may require surgery but is not always indicated. Surgery is more common in active patients. Grades IV, V, and VI are severe separations and all require surgery. Other ligament damage or tears, like a slap injury, can mimic an AC separation and often require surgery but should remain on the differential diagnosis when working up shoulder trauma. Setting expectations is key. Patients with a grade 1 or 2 separation should expect 6+ weeks of limited range of motion and up to 12 weeks until return to full function. Cosmetically there may be a persistent bump on the shoulder. References van Bergen CJA, van Bemmel AF, Alta TDW, van Noort A. New insights in the treatment of acromioclavicular separation. World J Orthop. 2017;8(12):861‐873. Published 2017 Dec 18. doi:10.5312/wjo.v8.i12.861   Summarized by Jackson Roos, MS4 | Edited by Erik Verzemnieks, MD