Sukhasana translates as
Known fondly as a a fundamental, basic, simple crossed leg pose. However, for many people it ain't that easy! There is already many resources out there which will tell you that the pose is to allow us to sit comfortably so we can move into meditation. As the Sanskrit translation explains the essence of the pose is to be able to sit with ease, so it should be about sitting anyway you can with ease.
It is totally okay to not find this 'basic pose' easy. For us in the West we have the fortune to have comfortable chairs, sofas, cars on which to sit comfortably. However, we need to understand the impact of these habits on our body. Sitting encourages you to lean back and sink through the middle of your body, weakening the abdominal and back muscles. Sitting for prolonged periods can make the muscles tighter, for example, if the pelvic floor is tight this can result in tension in the hips and surrounding pelvic muscles, this could pull the tailbone down.
If you do't have hips that can externally rotate or have abduction in the hip joints (the knees don't open outwards easily) then your thigh bones may not settle deeply enough into the hip sockets and into the sitz bones. So for them they will never feel at ease or comfortable in this posture.
There are two things we can do to assist with helping us with Easy pose. Firstly, come to sit in Sukhasana and observe your legs. Are the knees higher or lower than the hips? There are advantages and challenges in making a choice here on which option. So in the example above where the knees don't fall open, then having the knees higher than the hips can assist in gravity releasing the thigh bone into the hip socket.
Now, if your feel tight in your lower back and across the sacrum (back of pelvis) Then having the knees higher than the hips can make the pelvis tip backwards and this will instead of creating a lengthen spine, it will start to round. If you then try to straighten the spine, as us yoga teachers instruct, you are going to feel exhausted in your back, because of the muscles in the back and hip are working. So this is never going to feel comfortable or at ease!
So what about where we have the knees lower than the hips? To so this we would have the elevate the sitz bones (So we sit on a blanket, prop, cushion) This will prevent to pelvis from tipping back and really helps with the lumber (lower back) What we just have to check is that the pelvis does not tip too far forwards (anterior)This would then great a over exaggerated curve in the back.
OMG I hear you shout, so which one is right and this is more difficult than easy!
The goal I want you to experience when you next revisit this pose is which position of the legs allows for the weight to fall most clearly from the spine and through the pelvis and down into our sitz bones, regardless of high or low the knees are to the pelvis. So it might mean you do need to raise your seat and use a prop under the sitz bones until we have worked enough mobility in the pelvis and legs. Have a look at the How To.. for more and to see how to use the props. Try it out and take note the next time you come into the pose, so you experience a well-aligned Sukhasana which in turn will create the conditions for a relaxed yet alert state in both the body and mind.