Question, Asana-specific (Video): Use of ropes for flexed knees in case of knee injury

Why and how do you use ropes/ belts behind the knee when we completely flex (bend) the knee in positions like Virasana or Padmasana?

Tagwords: q&a, knee injury, knee therapy, healthy knee, ropes, Virasana, Padmasana, Baddhakonasana