The incidence of unilateral minor heterotopic ossification after primary total knee arthroplasty is still unknown, but bilateral severe heterotopic ossification is rare and has not been reported before. Presented in this report is a 60-year-old female patient who developed bilateral knee pain and stiffness 2 weeks after primary total knee arthroplasty. Her weight was 70 kg and body mass index was 32.2. Preoperatively, she had bilateral varus deformity of both knees. X-rays taken 3 months after surgery revealed bilateral severe heterotopic ossification. The patient had been on non-operative treatment (including anti-inflammatory drugs and physiotherapy). There was a marked improvement 6 months after surgery. This case report showed the non-operative treatment may produce acceptable results for patients with severe bilateral heterotopic ossification after primary total knee arthroplasty, and exerted no influence on the final clinical outcome.