Should we bend our knees in Uttanasana?

I was teaching my Dad Surya Namaskar A in preparation for teaching week. As I know he is super inflexible, when it came to Uttanasana I just rattled off on autopilot, “bend your knees until your belly touches your thighs”.

He asked, why?

I knew the answer had something to do with lengthening the spine. However, this doesn’t apply to me. Whenever I’m in bent knees Uttanasana, I don’t feel like my spine is lengthening or that I’m stretching out my lower back. Hence Uttanasana feels more like a hamstring stretch to me, which is fine, because I love stretching out my hamstrings anyway. But then I wondered, why not just do Uttanasana with straight legs?

So I went onto google to find out why, and surprisingly discovered that apparently the (online) yoga community is very divided about whether or not to bend your knees in Uttanasana or not.

When you bend your knees in Uttanasana, the hamstrings become slack, which relocates the stretch to your low back. By bending your knees you are able to gain more mobility in your pelvis, as the hamstrings are able to relax, and the pelvis can tip forward.

But some websites have stated that stretching the low back can be problematic as most people have very weak back muscle, and stretching a weak muscle leads to greater weakness and instability.

I don’t know what the correct answer is, so I don’t really have a conclusion to this – except that its fascinating to read different viewpoints on yoga poses and that teaching my Dad has made me realise the importance of questioning why do we do each thing for every asana.