Heterotrophic ossification (HO) is a reactive disease that is defined as the formation of mature lamellar bone in the soft tissue but it is rarely associated with loss of motion and stiffness. The reported incidence of HO after total knee arthroplasty (TKA) ranges from 1% to 42%. We experienced a case of HO adversely affecting the ambulation of the patient as a result of the severe ankylosis of the knee after TKA. We report this case with a review of the relevant literature.