Staying at your recommended weight helps prevent osteoarthritis of the knees, hips, and spine, reduces the stress on these weight-bearing joints, and reduces pain in joints already affected.Once you have osteoarthritis, losing weight also can relieve the stress and pain in your knees.taying at your recommended weight helps prevent osteoarthritis of the knees, hips, and spine, reduces the stress on these weight-bearing joints, and reduces pain in joints already affected.