Despite the available classifications, diagnostics and treatment of acute acromioclavicular joint (ACJ) injuries are still vague and challenging for trauma and shoulder surgeons. This study aimed to evaluate the dynamic radiographic as well as clinical outcome of operatively and conservatively treated Rockwood (RW) type III and IV ACJ dislocations. All patients with RW type III and IV ACJ dislocations between 2009 and 2016 (n = 226) were included in this retrospective data analysis with a prospective follow-up examination. According to their injury classification, patients were subdivided in an operative and conservative treatment group. Examiner blinded clinical evaluation including the constant score (CS), American shoulder and elbow surgery (ASES) score, the acromioclavicular joint instability (ACJI) score, visual analog scale (VAS), bilateral force measurements, and posttraumatic/postsurgical sequelae were assessed. Fluoroscopic evaluations including dynamic stability assessment with functional axillary views were performed for every patient. For follow-up examination (mean 4.8 years ± 0.3 SEM) 56 patients (29 RW type III, 27 RW type IV) were available. In patients with RW type III ACJ dislocations [operative (n = 10); conservative (n = 19)] prolonged duration of treatment was seen in operatively treated patients (p