The first time I saw an orthopedist about my bum hip, the nurse pointed to a row of smiley faces on the wall—six of them, with numbers and short phrases underneath. "What number is your pain?" she asked, waiting as I scrutinized the scale. Face One looked like a toddler on a swing ("Doesn't hurt at all"), but Face Two had lost her innocence ("Hurts a little"). Face Four looked as if she had a toothache ("Hurts even more"), while Face Five's smile had turned upside down ("Hurts a whole lot"). Face Six had tears running down her face ("Hurts all the time"). She looked as if a horse was standing on her foot.

This was not much to go on—the smiley face equivalent of a Rorschach test—but I did the best I could. My hip hurt all the time, thanks to a mild case of dysplasia I had hiked, biked and run with all my life. Now the cartilage was gone so that even sleeping hurt. I looked at the scale again. I definitely was not on the smiling end of the scale.

The nurse glanced at her watch, twirling her pen between her fingers.