In May 2003 I took three fast hikes in four days, and could barely walk the following day. Did something bad to my left knee, and have only been able to resume hiking (carefully!) in the last few weeks. Only resumed walking and hiking after reading in this book that (limited) exercise of an injured knee is encouraged, and in some cases the only treatment.
The author notes that considerable progress was made in the 17 years between when he began his practice to when the book was written. Since the book was written about 17 years ago, you might expect an update to the book is in order.
As you might guess from the remainder … I have a teenager :).