We describe an unusual case of a 43-year-old woman who had developed bilateral spontaneous periacetabular fractures secondary to severe myoclonic contractions. The absence of antecedent history of trauma and detection of muscular spasticity at presentation prompted neurologic investigations that led to the diagnosis of multiple sclerosis in this patient. The fractures were treated successfully by open reduction and internal fixation initially. Since fracture reduction was delayed for almost 1 year, a special distraction frame had to be used. Deterioration in the medical condition of the patient with return of severe spasticity caused a dramatic failure of the fixation on one side 2 years later. This case report confirms that fractures, usually requiring high-impact trauma, can and do develop spontaneously in patients with sustained myoclonic contractions, and these fractures can be the presenting indication of an underlying neuromuscular disorder.