Entrapment of middle cluneal nerves as an unknown cause of low back pain

Figure 1 Photo taken during the surgical release of a left-side middle cluneal nerve. Medially to the posterior superior iliac crest (P), the MCN is identified passing under the superficial layer of the long posterior sacroiliac ligament. The nerve is seen to be entrapped under the deeper layer of the long posterior sacroiliac ligament where it penetrates the ligament (arrow). The yellow and red tapes have been used to lift the proximal and distal portions of MCN branch, respectively. MCN: Middle cluneal nerve.