We report the arthroscopic identification of combined morphological variants of the acetabulum in an adult. The combination of iliopubic and ilioischial grooves has not been reported before. Preoperative radiographic and MRI failed to detect the lesions. These grooves strongly suggest incomplete fusion between the three limbs of the triradiate cartilage. When identified, this condition should not be treated as pathological but as a rare anatomical variant. Hip arthroscopy is a competent tool in discovering such asymptomatic cartilage abnormalities and subtle anatomical variations even in the presence of normal preoperative imaging.