In all, 69.23% of the cases (95% CI, 48.21-85.67%) were not explained by the classic risk factors. In view of the absence of other diseases and otherwise unremarkable parameters, we consider mechanical damage of the lesser pelvis not to be solely responsible for AMS. Further observations in patients with AMS, with and without endometriosis, may be able to contribute to research into the actual etiology of the condition.