We report the case of a 67-year-old male with bilateral proximal tibiofibular synostosis, presenting with unilateral symptoms. The patient complained of pain around the left fibular head, which was attributed to incomplete bone bridging between the proximal tibia and fibula; he underwent proximal fibular head resection, which alleviated the pain and improved knee mobility. Eleven months later, the patient continued to be pain-free and did not experience any adverse effects. An examination of this case and a review of similar cases revealed that participation in sport activities such as long-distance running may be one of the causes of proximal tibiofibular synostosis. In this report, we have also reconsidered the classification of proximal tibiofibular synostosis and provided information for a better understanding of this unusual condition.