Distal femoral cortical defects, irregularities, and excavations.

A review of available radiographic and pathologic material revealed evidence that two distinct anatomical variations may be found on the posteromedial aspect of the distal femur. One, the femoral cortical irregularity, is a common finding on clinical radiographs, shows a definite predilection for children and adolescents, and is closely located to the site of attachment of tendinous fibers of the adductor magnus muscle. It is almost certainly related to stress, and can be associated with a degree of periosteal proliferation that simulates malignancy. In a study of prehistoric adult femoral specimens, the second lesion, the femoral cortical excavation, was a frequent finding. However, it appears to be less common in clinical radiology. It occurs at the osseous site of attachment of the medial head of the gastrocnemius, which supports a stress-related pathogenesis. Its relationship to fibrous cortical defects is not clear.