For more than 35 years now, "NBC Nightly News' anchor Brian Williams has tolerated a severe knee injury suffered back in High School. At 54, he's finally decided to so something about it - making the announcement during "Nightly News" that he'll be taking a leave of absence from the anchor desk for a few weeks. 

"[The pain] is now costing me sleep. I reached a point recently in the last 12 months where I decided this has to happen and to be mathematical about it, I've lived now most of my days, so worst-case scenario, if this doesn't go perfectly well, which it will, it can't hurt more than it hurts now," he said.

In an effort to educate viewers on his upcoming knee replacement surgery, Williams enlisted the help of Dr. Nancy Snyderman to explain the procedure. 

"It's an operation some 655,000 Americans will have this year, nearly double the total from ten years ago," reports Snyderman. "Total Knee Replacement is often the last resort for men and women, many of them baby boomers, who have pushed themselves to the point where the cartilage in the knee has worn down, resulting in bone-on-bone contact and often excruciating pain." 

Snyderman goes onto explain that recover from such procedures can take anywhere from three weeks to three months for simple walking - and up to a year for full use of the knees again. As for Williams, his knee damage isn't so much from age as it is from a High School football game that resulted in helmet-to-knee contact. 

"It reversed my knee — they don't recommend that," Williams said on "Nightly News". "I loved playing a team sport. I loved every minute of football. I've paid a very high price for what's been confirmed to be the single-worst New Jersey High School Catholic League football career in history."

Check out Williams interview and Snyderman's report on the procedure below. 

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Brian Williams to undergo knee replacement surgery
'NBC Nightly News' anchor says the injury to his right knee dates back to a high school football injury.