Heterotopic ossification (HO) is a rare condition usually related to trauma or neurologic damage. It can affect all bone joints but is more frequent at the hip, particularly following total hip arthroplasty. This condition leads to significant impairment of life quality due to ectopic bone formation which causes functional loss. Here we describe two cases of patients presenting symptomatic HO classified as Brooker III following total hip replacement. One of them was treated prophylactically with external beam radiation, few hours before surgery for prosthesis revision. The other one, received radiotherapy as sole treatment with the intent of symptoms palliation. During the follow-up visits, the first patient didn't show any HO recurrence and had a significant improvement of his symptoms, namely the claudication; the last one achieved a significant relief of pain and showed an improvement on his functional capability. These cases show the potential benefit of radiotherapy as prophylaxis or as sole treatment of symptomatic HO.