Heterotopic ossification (HO) is the formation of aberrant lamellar bone within soft tissues. The incidence of HO formation following total hip arthroplasty (THA) is 20–40%. Patients at the highest risk for developing HO are males with preoperative hypertrophic osteoarthritic conditions, hip ankylosis, or the presence of HO elsewhere. HO may present within the early postoperative period as pain that resolves once the bone matures but can later create restrictions to the hip range of motion. The Brooker classification is the most widely used system for grading HO, with grades III and IV potentially representing clinically significant functional limitations. Effective prophylaxis can be achieved with either indomethacin 25 mg TID for 10 days or 700 cGy radiotherapy given perioperatively. Anti-inflammatory prophylaxis is recommended for patients less than 65 years of age or with prior history of radiation/malignancy, while radiotherapy is recommended for those at high risk for gastrointestinal or renal damage from anti-inflammatories. Surgical excision should be considered for those who have significant functional limitations or worsening lumbopelvic disease. Excision tends to lead to improvement in motion.