Given the importance of the relationship between the posterior division and the obturator externus muscle as one of the possible causes of posterior division neuropathy, we identified the following classes of variations: i) the posterior division of the
obturator nerve passes over the musculotendinous aponeurotic arch, anterior to the obturator externus muscle (32 out of 56), ii) the posterior division of the
obturator nerve emerges from the proximal quarter of the substance of the obturator externus muscle, perforates it and descends anterior to its distal part (22 cases out of 56), iii) the posterior division descends entirely posterior to the obturator externus muscle, emerging from its inferior border (2 cases out of 56).