Nationwide epidemiologic study of osteochondroma in Japan: Analysis of 4843 cases from the bone and soft tissue tumor registry

and Mann-Whitney U tests. A total of 4,843 patients (2,911 males and 1,932 females; male-to-female ratio, 1.5:1) were included. SO accounted for 77.1% and MO for 22.9% of cases. The median age at diagnosis was 15 years, and nearly half of all patients were younger than 20 years. The lower limb was the most frequently affected region (65.2%), followed by the upper limb (26.3%) and pelvis (4.5%), with the femur and tibia being the most common sites. MO presented at a significantly younger age and exhibited characteristic symmetric involvement of multiple long bones, particularly in the lower extremities and forearms. Surgical intervention was more common in SO than in MO (49.9% vs. 37.9%, p < 0.001). This study provides the largest epidemiologic overview of osteochondroma in Japan and highlights distinct clinical patterns between SO and MO, offering essential population-based evidence to guide future clinical management and surveillance strategies in Asian populations.