The osteochondroma is a cartilage-capped exostosis resulting from an error in the regulation of normal chondrocyte proliferation and maturation that leads to a normal bone growth. Although exostoses are benign lesions, they are often associated with characteristic progressive skeletal deformities and may cause clinical symptoms. Surgery can prevent progression and provide correction for certain deformities. We experienced a rare case of solitary osteochondroma in a 21-year-old male which caused the valgus deformity of the ankle.