We report a rare case of vesico-acetabular fistula due to an improperly treated pelvic fracture with urinary stone formation in the joint cavity. This complication was related to an unrecognized mechanism of bladder wall entrapment in the acetabular floor defect during weight bearing. This situation led to several mistreatment decisions in our case and should be always considered by urologists dealing with patients after major pelvic trauma. In this case report, we analyze the publications related to this problem, discuss the main mechanisms of bladder wall damage after acetabular fracture, and propose tips for diagnosis and treatment.