Acquired heterotopic ossification (HO) has been well described in the literature as a recognised complication following spinal cord injury, traumatic brain injury and joint arthroplasty. Commonly, the large proximal limb joints are affected. The underlying mechanisms remain poorly elucidated. Post-stroke hemiplegia as a cause of neurogenic HO is rare, and no published reports of HO occurring after anoxic brain injury in adults have been documented. This paper reports two unusual cases of acquired HO: (1) polyarticular HO involving the ankle joint in a 24-year-old Chinese female who suffered severe anoxic encephalopathy following near drowning, which resulted in persistent vegetative state; and (2) elbow HO in chronic post-stroke hemiplegia occurring as a complication of repeated forceful manipulation by a traditional practitioner in a 46-year-old male.