[Uncommon etiology of cruralgia].

A 58 year old man suffered from low back pain. Physical examination showed asymmetry of the quadriceps and slight motor deficiency of right leg. Plain radiography of the pelvis revealed a large osteophyte, developed anteriorly at the low part of the right sacro iliac joint. CT exam of lumbar spin was normal. But, it confirmed osteophyte of right sacro iliac. Percutaneous injection of a small quantity of xylocaine under CT guidance in the site of the osteophyte behind crural muscle was marked by immediate disappearance of the pain, confirming the site of conflict between the crural nerve and the osteophyte. The patient was treated by injection of corticosteroid at the same location. Recovery was good.