Your aching feet really shouldn't.

Not according to Dr. Arthur E. Helfand of Thomas Jefferson University Hospital in Philadelphia."A great misconception is that feet are supposed to hurt," says Helfand, an adjunct professor of podiatric medicine. "Feet are amazing mechanisms for balance and stress - they are built to do the job.

"Problems arise when people misuse the foot's structure by walking on inappropriate surfaces with improper protection, by not tailoring shoe size to foot size, and by not practicing maintenance of their feet."

He reminds us that concrete is the hardest surface on feet. Sidewalks provide no absorption for the shock of each step. The result is stress and shearing of foot muscles, tendons or bones. The remedy is rubber or thick leather soles.

High heels are ill-advised for sustained walking. They push the pressure of each step to the front of the foot, causing imbalance of the whole area.

While people today are attuned to matching shoes to their active needs, he says they are unaware of proper fit.

"You can't buy shoes by a standard size," he says. "Every manufacturer has a different sizing system depending on the last, which is the original shape and sizing model for each shoe."

The discomforts of a small shoe are obvious. Those that are too large also cause problems by building friction and blisters when the foot slides within the shoe.

Helfand says most foot problems could be avoided. Blisters are caused by ill-fitting shoes; corns and callouses from excessive pressure on one part of the foot; stress fractures relate to abnormal and consistent pressure; bunions are an inherited tendency aggravated by these same causes. Heel spurs are evidence of foot strain. Tendonitis is caused by excessive stress on the tendon. Bursitis is caused by repeated injury to the ball of the foot.

As for fallen arches, Helfand says, "Arches don't fall. The foot becomes misaligned and rotates."