Q Each year half a million knee replacements are done in this country, and almost as many hip replacements. These metal implants almost always set off the alarm in the screenings -- I know. But the screening of a traveler with an implant is quite variable. Why doesn't the Transportation Security Administration have a standard exam for us "bionic" travelers?

A We've criticized the TSA for treating all of us as potential evildoers, and in an interview last month, TSA administrator John Pistole said the agency was moving away from its one-size-is-the-right-size philosophy. In the past few months, we've seen a range of new screening initiatives to address some of the more obvious issues. As the TSA continues to slice the pie thinner and the 75 million baby boomers age, there one day may be a screening procedure for those people with replacement parts.

That day probably won't come until the TSA uses uniform screening technology. When you go through airport security, sometimes you get the metal detector and sometimes you get the imaging machine. The former is more apt to sound the alarm for people with artificial joints, so if it's an option, choose the imaging machine or ask for the pat-down.

On its website, the TSA has a page called "Travelers With Disabilities and Medical Conditions" (www.tsa.gov/traveler-information), which covers a range of issues. An internal medical device such as a pacemaker? You shouldn't be screened by a metal detector but, instead, by an imaging machine or by a pat-down, the website says. If your child has a disability? He or she "can be screened without being separated from their parents or guardians."

The TSA also offers a card that you can print at home (there's a link to it from the travelers with disabilities page) that allows you to describe your issue. You still must be screened; the card merely allows more discretion when you're dealing with a TSA agent.

If you have questions about screening, you can contact TSA Cares at 855-787-2227 between 5 a.m. and 8 p.m. weekdays or 6 a.m. to 5 p.m. weekends and holidays. Those who are hearing-impaired can email TSA-ContactCenter@dhs.gov or use a relay service.

Today's column comes from Catharine Hamm of the Los Angeles Times.