Here are some examples of postures that compromise the body's original design and result in muscle and joint dysfunction and no doubt pain and problems. If there is knee or hip pain, the knee and hip are only trying to tell you they have lost their alignment and integrity that is why the cartilage is wearing down from uneven pressures inside the joints. Just look at the uneven pressures in the photo to the left. Good posture is the ability to maintain structural integrity of the joints.
In the drawings to the left, the primary joints, ankles, knees, hips and shoulders, are not lined up vertically and horizontally. There are shoulder and hip elevations and rotations. There is valgus (knock knees) knee stress and varus (bow legs) knee stress, tibial torsion (low leg is torqued relative to the thigh/knee). Would these people experience pain? In time, no doubt because they have compromised the original structural design of the body.