THANK YOU.

♪♪ >> MARK: APPARENTLY, I'VE NOW REACHED THE AGE WHERE PEOPLE HAVE A "BAD KNEE."

MY PROBLEM IS I'M NOT SURE WHICH ONE IS THE BAD ONE.

MY CURRENT GOOD KNEE USED TO BE MY BAD KNEE.

NO REASON, JUST ONE DAY IT STARTED ACTING UP.

IT DIDN’T HURT ALL THE TIME.

ONLY WHEN I WOULD RUN, OR WALK, OR STAND STILL, OR LIE DOWN.

IT WAS FINE WHILE WATCHING TV.

I CAN DO THAT FOR HOURS, WHICH IS LIKE MY VERSION OF A MARATHON.

GRADUALLY IT GOT BETTER.

MEANWHILE, THE OTHER KNEE, WHICH IS NOW THE BAD KNEE, WAS ONCE THE GOOD KNEE, BUT NOW SEEMS TO BE GETTING WORSE, MAYBE FROM TRYING TO MAKE UP FOR THE GOOD ONE, WHICH USED TO BE BAD.

SO NOW THE FIRST KNEE IS THE GOOD KNEE, WHICH USED TO BE BAD BUT IS NOW GOOD COMPARED TO THE NEW BAD KNEE.

IT’S NOT TERRIBLE.

IT HURTS DURING THE DAY, ACHES AT NIGHT.

WHEN I STAND UP, IT SOUNDS LIKE SOMEONE CRUSHING TRISCUITS WITH A ROLLING PIN.

IT’S ONLY RELATIVELY BAD -- IT WASN’T TRYING TO BREAK INTO MY ONLINE BANK ACCOUNT OR ANYTHING.

SO I GOT A KNEE BRACE.

GENERALLY, IF SOMETHING HURTS, YOU DON'T WANT TO SQUEEZE IT.

YOUR KNEE STILL HURTS, AND, PLUS, YOU GET LITTLE DENTS IN YOUR LEG.

A BRACE REALLY ONLY WORKS BEFORE IT STARTS HURTING.

YOU PROBABLY HAVE TO START EARLIER, LIKE IN KINDERGARTEN.

I ALSO TRIED PUTTING ICE ON IT.

THEN IT HURTS AND IT'S FREEZING.

THE NEXT STEP IS WHEN THE BAD KNEE STARTS GIVING OUT, AND THAT’S WHEN YOU SUDDENLY FALL OFF THE CURB AND LAND IN TRAFFIC.

I THINK IT’S TRYING TO GET RID OF THE GOOD KNEE.

THEN IT WOULDN’T BE THE BAD KNEE ANY MORE.

IT WOULD BE THE ONLY KNEE.

SO YOU GO TO YOUR DOCTOR.

THEY DO AN X-RAY AND SEND YOU TO ANOTHER DOCTOR WHO CAN INSTALL BRAND-NEW KNEES.

THIS DOESN'T WORK WITH MOST OTHER BODY PARTS.

GENERALLY, YOU HAVE THE SPLEEN YOU ORIGINALLY GOT.

BUT THAT’S THE WORST-CASE SCENARIO.

I’M NOT SHOPPING FOR REPLACEMENT PARTS YET.

MEANWHILE, I NEED MY KNEES.

TURNS OUT EVERY DAY IS LEG DAY.

I HAVE TO DO SOMETHING, WHILE I STILL HAVE A LEG TO STAND ON.