Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disease. It is characterized by widespread soft tissue ossification and congenital stigmata of the extremities, affecting all ethnic backgrounds. The worldwide reported prevalence is approximately 1/2,000,000. Based on history and clinicoradiological findings, FOP should be diagnosed as early as possible and noninvasively. The hallmark of diagnosis of FOP is bilateral great toe anomaly present from birth. Misdiagnosis may lead to inadvertent managements, such as manipulations, biopsies, and surgery. Surgery, till now, does not seem to have any role in the management of this condition and may lead to further trauma and disease progression. FOP may be precipitated due to trauma to muscle. In masticatory muscle, it mainly affects masseter muscle and presents with symptom of trismus. Herein, we present a case of FOP which presented to us with trismus after wooden thorn injury and immobility of the left leg. This article also emphasize on diagnosis, precaution, and treatment of disease.