Osteolysis is a significant long-term problem in hip arthroplasty. Plain radiographs are the routine investigation of choice for monitoring hip arthroplasty patients; however, the recognition of clinically significant osteolysis can be challenging. We present two case reports of arthroplasty patients with ballooning and expansion of the superior pubic ramus with loss of the normal concavity of the ilio-pectineal line. Both patients subsequently displayed massive pubic osteolysis at the time of revision surgery. We suggest that the presence of convexity of the ilio-pectineal line/superior pubic ramus indicates established pelvic osteolysis.