What's happening is that you have FDD: "Franklin Delano Derriere." You may know that FDR had almost no muscle over his ischial tuberosities, the bones in your lower pelvis on which you sit. If your bum hurts sitting on a cushion, imagine the pain Roosevelt must have experienced sitting in his wooden wheelchair that had no cushion at all.

You're developing pain because, as your butt muscles get smaller over time, your ischial tuberosities are pressing harder on the thinning tissue underneath. Your doctors don't find pressure sores on your skin because fortunately, polio survivors don't typically get decubitus ulcers since they have intact sensation and good blood flow to the skin. In 24 years we have never seen a polio survivor with a pressure sore. But we're seeing more and more cases of FDD.

As you've discovered, foam and even gel are often not soft enough to cushion an unpadded bum. What you can try is a light, air-filled cushion that gives you gentle support as it distributes weight away from your ischial tuberosities. The granddaddy of air-filled cushions is the "BBD," Bye-Bye Decubiti (around $250 at easypivot.com), an inflatable pillow with "dimples" that help distribute your weight. A newer "dual-chamber" version allows you to fill the left and right sides with different amounts of air.

Roho Dry Floatation cushions, with rows of air-filled cells that redistribute pressure as the user moves, can be purchased online [SpinLife.com or Southwest Medical] for around $280. Star cushions (around $425 at starcushion.com) have about 100 banana-shaped cylinders that fill with air. Some cushions are designed to fill all cylinders with the same amount of air. Others allow the front and back halves to be filled with different amounts of air, allowing you to raise up your small buns in back so that they are level with your relatively larger thighs up front. Some cushions allow the front and back and the left and right portions of the cushion to be filled individually to give stability to polio survivors who have, say, a smaller left cheek but a larger right leg.

The newest and most expensive air cushions are from Aquila (around $675 at aquilacorp.com). Instead of having many identical air-filled cylinders, their Custom Air cushion has 18 compartments, long and flat in front to support the thighs, smaller, wedge-shaped or round in back to support the butt. Each compartment has about 2 inches of foam at its base. Off-the-shelf, Aquila cushions let you inflate the front and back compartments separately. But, the company says it will custom-build cushions that will allow you to inflate any grouping of compartments to conform to your unique shape. Also, Aquila cushions inflate with a blood-pressure cuff bulb (versus a bicycle tire-type pump for the other cushions) attached to an electronic LED pressure display, so that you can actually "see" how much air is in the compartments.

Once you find a cushion that will tenderly cradle your skinny bum, you also have to consider how the rest of you is positioned. For your butt to be comfortable, you have to make sure that your footrests are at the proper height and angle and that you have a solid back with lumbar support, like the Jay 2 back (sunrisemedical.com), not just the canvas sling wheelchair back.

Proper bum and back positioning will also fix the right hip and neck pain you get late in the day. That pain may be due to muscles shortening and going into spasm as you lean right to shift your weight off the cheek that hurts. Too, you could have bursitis in your hip, also due to putting too much pressure on your right hip joint as you shift your weight away from the offending cheek.

So, all things being "unequal," the fix for your FDD may be, as is spring, "in the air."