This is a rare case report in an elective orthopaedic setting, in which a 72-year-old man without known urologic disorders presented with a 6.2 l post-void residual urine (PVR) before a planned knee arthroplasty surgery. The PVR was found because of a newly established local guideline in an orthopaedic department regarding examination and treatment for PVR. The guideline was made in collaboration with urologists to improve the quality of treatment. Early diagnosis and treatment may prevent chronic bladder injury, urinary tract infections, urosepsis and kidney damage.