Heard this on a radio show a couple of days ago...
For every pound of body weight you gain, your knees gain three pounds of added stress; for hips, each pound translates into six times the pressure on the joints.
With every step you take, your moving body puts pressure roughly equal to three times your weight on your hips and knees.
Being only 10 pounds overweight increases the force on the knee by 30-60 pounds with each step.
Overweight women have nearly 4 times the risk of knee OA; for overweight men the risk is five times greater.
If you lose just 1 pound, you reduce by 4 pounds the force your knees must absorb when you walk.