INTRODUCTION. Hereditary multiple osteochondromas (HMO) is a genetic skeletal disorder caused by defects in exostosin glycosyltransferase 1 (EXT1) or 2 (EXT2) genes. It develops mainly in the growth period and causes multiple osteochondromas (OC) in the physis of the long bones, leading to discomfort and deformities. This study aimed to investigate the anatomical distribution of OC, the frequency of deformities of the lower limbs, scoliosis and surgeries performed in a cohort of patients with HMO at the time of their enrolment in a regional surveillance programme. METHODS. The study population included HMO patients from the Centre of Heritable and Complex Diseases (CAKS) in the Region of Southern Denmark. Information on surgical procedures and age at the time of diagnosis was obtained from medical records, while deformities were evaluated on early-onset scoliosis (EOS) scans from time of enrolment in the CAKS. RESULTS. A total of 54 patients were included and 44 patients (82%) had an EOS scan. All except one (98%) HMO patient had OC in the knees at the time of their EOS scan. A total of 12 patients (27%) had leg length discrepancy, 30 (68%) had genu varum or valgum and 13 (30%) had scoliosis. The HMO patients had undergone a median of 2.0 (0-14) surgeries, where a median of four (1-23) OC were removed, mostly in the lower limb (68%). CONCLUSIONS. The majority of HMO patients in this cohort suffered from major anatomical burdens, leading to multiple surgeries and deformities. We suggest that a programme, such as the CAKS surveillance programme, may be beneficial to screening and follow-up of OC and deformities in patients with HMO. FUNDING. None. TRIAL REGISTRATION. Not relevant.