To evaluate the incidence of HO in single and double-level Discover disc replacement, a relatively new type of artificial implants. Moreover, the related clinical and radiological outcomes and the possible influencing factors were analysed. Twenty-six women and 39 men were retrospectively followed-up for 5 years. They consecutively underwent one or two-level cervical Discover arthroplasty. Clinical outcome was assessed using the visual analogue scale (VAS). The angular range of motion (ROM) was calculated with periodic dynamic X-rays. A Student’s t test was used to analyse the association between the occurrence of HO and various risk factors. Among the 65 patients enrolled, the overall incidence of HO was 7.69% and the mean follow-up was 63.29 ± 11.90 months. All the cases were diagnosed as Grade III or Grade IV. The mean VAS showed immediate postoperative improvements and the mean ROM was partially maintained. No displacement of the prostheses was detected.