A 58 years old man suffered from low back pain. Physical examination s
howed asymmetry of the quadriceps and slight motor deficiency of right
leg. Plain radiography of the pelvis revealed a large osteophyte, dev
eloped anteriorly at the low part of the right sacro iliac joint. CT e
xam of lumbar spin was normal. But, it confirmed osteophyte of right s
acro iliac. Percutaneos injection of a small quantity of xylocaine und
er CT guidance in the site of the osteophyte behind crural muscle was
marqued by immediate disappearence 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.