Cortical abnormalities at the distal postero-medial femoral metaphysis may be relatively common. We reviewed the plain radiographs of 197 knees in 130 children aged between 5 and 12 years to investigate the incidence of distal femoral cortical irregularities (DFCI) and their association with symptoms. An adductor magnus lesion was found in 15% of cases, with an even number of irregular and cystic lesions. A medial gastrocnemius lesion was found in 5% of cases, but no association was found between symptoms and the lesion. Overall, lesions were found in 25% of cases aged 5 to 9 years, but in only 13% of cases aged 12 and 13 years. Boys showed a higher incidence of both adductor magnus and medial gastrocnemius lesions. DFCI is a benign, self-limited entity and a relatively common radiologic finding. Regardless of whether or not symptoms are present, imaging findings should be carefully interpreted to avoid unnecessary diagnostic and invasive therapeutic procedures.