Originally developed by Karo in 1986, the design is based on understanding what happens to your body when you sit. The underlying principle of a kneeling posture chair is to maintain an ‘open’ pelvis while you are sitting. This reduces the strain in your lower back that normally occurs when you sit on a conventional chair. An ‘open’ pelvis is when the angle between your spine and thighs is greater than 100 degrees. The pelvic angle on the Wellback Kneeling Chair is 110 degrees, which is ideal. How does a kneeling chair work? The Wellback Kneeling Chair is rated to 120kg and has a 12 month warranty.