Knees not above hips at least I would say. Lower back problems often seem to come from bad posture, bending foreward too much, and loosing the s-shape of the spine. Having the seat tilted foreward, and the knees somewhat lower than the hips, makes the lower back tilt foreward, and encourages the s-shape. Whith the seat tilted backwards, its the other way around.
Edit: Recliner chairs is a bit different, because the whole back is supported. But I believe a good reclining chair (and Cinema and car seats and so on), has a support in the lower back that encourages the s-shape, instead of just being scoop-shaped. Otherwise it is possible to use a small pillow, or you can look up the "McKenzie Lumbar Roll" for instance.
Wilson PS Classic, Gosen OG Micro 16, 26 kg.
Last edited by Povl Carstensen; 01-14-2013 at 12:23 AM.