2 – Anatomy: The initial trajectory of the posterior femoral cutaneous nerve

The posterior femoral cutaneous nerve (PFCN) exits the pelvis together with the sciatic and pudendal nerves through the greater sciatic foramen underneath the piriformis muscle. The PFCN and the sciatic nerves run laterally covered by the gluteus maximus, and the pudendal nerve deviates infero-medially into Alcocks canal.

At the inferior margin of the gluteus maximus the inferior cluneal nerves branch off the PFCN. The perineal branches branch off the PFCN below the ischial tuberosity. Hereafter, the PFCN runs superficial to the tendon of the long head of the biceps femoris, while the sciatic nerve dives deep to the biceps femoris. In the trajectory down to the popliteal fossa, the PFCN is sandwiched between the hamstrings – mainly the long head of the biceps femoris – and the fascia lata with its branches piercing the fascia lata to innervate the skin of the posterior thigh.

In the picture on the right the PFCN is depicted with magenta and its perineal branches with cyan colour. Long head of biceps femoris (green asterix), semitendinosus (red asterix), semimembranosus (blue asterix).