anon500 wrote:Due to what I perceive to be a lack of hip flexibility, even sitting on a zafu in quarter lotus position causes some knee discomfort in my right leg.
I have the exact same problem and it usually strikes the medial part of the knee. I am working on it with yoga hip openers as well. I use a chair and a kneeling bench (seiza) for sitting meditation as well - you could try those.
For me, there has to be some muscular tension to hold the body erect regardless of the position sat in. The key is not to be too tense and not to be too relaxed. I think it's normal.
I've found cross-legged sitting to be the most conducive to concentration. It's more stable than the other postures. I imagine full lotus is the most stable of all. The more stability, the easier it is to get balanced and concentrated.
I think if we're diligent and patient with our yoga hip-opening practice, we will reap the results eventually. In the meantime, we have to use "props" like stools in the like for sitting. Fortunately, walking meditation has fewer flexibility requirements!