We describe the first intraprosthetic dislocations of a 22 mm head in a dual mobility hip replacement in the literature. This case emphasises the importance of information gathering and planning when dealing with arthroplasty complications. Furthermore, it highlights the necessity of adequate muscle relaxation and analgesia when dealing with hip dislocations. A 78-year-old patient presented to the emergency department (ED) with a spontaneous dislocation of her left dual-mobility total hip replacement 3 months after first-stage revision surgery for infection. Reduction via manipulation under analgesia was then attempted in the ED but was ultimately unsuccessful; an iatrogenic intraprosthetic dislocation of the polyethylene liner was sustained. Several factors may have contributed to liner dislocation: a failure to appreciate the implant type, multiple manipulations in ED were attempted under analgesia, but no sedation or muscle relaxation was administered to the patient. The patient subsequently underwent revision surgery.