"Abstruse knotting techniques" would probably be more a more accurate phrase. I've listened in on two surgeons discuss at great length and in detail the merits of which knot and access path to use for, say, tying off a vein one-handed, by feel, when it's located somewhere behind another organ. The decision is complicated, so far as I was able to understand the conversation, by the patient's current blood volume and rate of loss.