Saturday, December 11, 2010

What Are You Doing for Your Knees the Other 98% of the Time?

Anyone who reads my book (to be available the first week in January, it appears) will see me, in chapter eight, engaging in a bit of "medical study deconstruction" -- namely, taking apart a large study that was done about the effect of physical exercise on knees and showing how it comes up short in a number of ways.

It was a fun and illuminating exercise (fun because, to my wife's dismay, I spend a lot of time with my brow furrowed, thinking about things). To those who wonder what insight a layman could possibly have into a formal medical study, well, you might be surprised. The application of basic logic will get you far in analyzing complex subjects, even without specialized knowledge. For instance, judging the truth of the statement "the green disarticulation contours were green" doesn't require an understanding of what disarticulation contours are, why they are drawn, how they are drawn, whether they should or should not have been drawn in this specific instance. To recognize the sentence is true, you just need to identify an identity: "green equals green."

Okay, that example may seem a bit trite, but my advice is not to let the "experts" scare you away from examining their work, cloaked in all its jargon and statistical raiments. At the very least, after a thoughtful examination, you'll be in a position to ask some good questions.

And one question I asked, regarding this study, was "What were somebody's knees doing the other 98 percent of the time?"

Let me explain: The study looked at people who exercised, to see if they were less likely to develop osteoarthritis of the knee later in life. One category of exercise, fittingly enough, was walking. They were asked if they walked for exercise, and if they did, if they went less than, or more than, six miles a week.

Through how the categories were constructed, the researchers made it sound as though six miles a week was a lot of walking. So I decided to do a little math.

Let's say Joe Smith walks six miles a week for exercise. How long does it take to walk a mile? Well, I've walked one in 13 minutes before, but the average is probably closer to 20 minutes. So that equals two hours a week total. How many hours is Joe awake each week? Let's say Joe gets a full eight hours of sleep a night -- an optimistic assumption, but we'll go with it. That means Joe is awake 112 hours (16 hours x 7 days).

Divide 2 by 112 and you get 1.8 percent: That's right, Joe spends less than 2 percent of his waking hours on walking for exercise. Why does that matter? I hope you can see now where I'm going with this. What's happening with his knees the other 98 percent of the time? That's HUGE. (And the study in question makes no mention of this as a potential issue.) After all, his knees don't just magically detach from his body whenever he happens not to be exercising.

One of my complaints about physical therapy stems from this 2/98 problem. My therapist laid out a program of exercises and stretches that took me ... about two hours total, each week. Yet he didn't seem concerned about what my knees were doing the rest of the time! He never asked me questions that I would ask any knee patient, knowing what I know now. (Do you lug things to work? Do you often carry a loaded backpack? If so, about how much does it weigh? Do you often carry a child around the house? If so, how big is the child? Do you navigate a lot of steps during a typical day? Do you run for a bus? Do you run at all during a typical day? If so, for what distance and how often? Do you squat a lot at work? Do you stand a lot at work? Etc., etc.)

These questions are important because they are the other 98 percent! If your PT isn't asking about the other 98 percent, I believe you need to do the asking and thinking yourself. Because your job/house/lifestyle/whatever greatly affects how you use your knees. And how you use your knees -- over 100 percent of your waking hours, not just 2 percent -- is a big determinant of how your knees feel (and heal), I learned during my recovery.


  1. Have you or anyone had just "weak knees?" For over 7 years, I have had this issue and have seen a variety of doctors, multitude of tests, physical therapy and still...same old..same old thing. I was wearing a rocker type shoe from Kmart for about 6 months and my weakness went away, but...then my feet started to tingle and get sore from them. It became too tried the Sketcher brand and the weakness came back. So now, I am back to a good pair of running shoes with good support wit weak knees. I am considering on seeking out another orthopedic surgeon's thoughts, but...because I am not in pain they feel nothing is wrong. If I wear knee supports the feeling goes away, but in several days, I get tingling in my feet. One doctor thought that since my knees are OK with supports that by realigning and tightening the knee cap, the problem would be solved. I should be happy that I don't have pain...but...a weakness all day can be just as brutal. No medication works on manage through the day. When I relax at home on the couch, the feeling will go away in about an hour and then the problem starts all over again the next day.

  2. Interesting comment. I am the one with this strange condition. I could type you a long story...but I will be brief. Prior to this condition, I have been physically active (road by bicycle, cross-county skiing and such. I am 5'10 and weigh about 130 lbs. This weak knee condition slowing emerged about 10 years ago. Initially I was instructed to do circuit training at my gym and such. It seemed to the months/years crept up, this weakness was more constant. The feeling in the knees are exactly that...a weakness within the knee area. They never feel like they are going to give out...just a darn feeling of weakness. I could be sitting at work and have that annoyance. Have tried pain meds,'s not pain, so nothing helps. And, I am not overweight, was physically active and have mystified doctors. As these years have transpired, I noticed that the rocker shoe removed this condition. I did have tingling in the feet with these shoes and was told that my shoe size 8 1/2 or 9 which was the wrong size, thus creating a tight foot-bed. Once I went up to a size 10 1/2 with an orthotic, the tingling subsided. Would bore you with more details, but had to resort to a normal shoe style. Recently, I had to adjust my new orthotics with my shoes due to smaller toe box and foot soreness. So,they reduced the arch material so my foot would not hit the seems within the shoe. Two days after the adjustments, the weakness in my knees came back. Two days ago, I purchased a shoe with a wider foot-bed and they built up the arch support and fingers crossed in day 2, the weakness in my knees are dissipating. So as you can see, their is a connection between the angle/alignment of the foot and my knees. I believe that my knees are slightly misaligned, thus creating the condition. Several summers ago, I rode my bicycle to and from work. It seemed to keep things in check, but as soon as the weather changed and I had to resort to driving...the weakness reappeared. In the past, the 3 P.T.'s were always mystified during the sessions and how my weakness would disappear and reappear. From all the orthopedic surgeons I have visited, only 1 suggested that I wear knee supports. During this 1 month trial, my weakness went away. Due to this, he had a plan of operating on the knees that would essential tighten the knee cap and properly re-align them for support. It's difficult to reach that decision, since other doctors said my knees are fine, but...the weak knee symptoms are quite debilitating. Through these years of experimentation, I now know there is a link between the alignment of my feet and my knees. So...I hope this addresses your logic. If anyone know of a good knee specialist in Ohio that has dealt with this condition I would appreciate a response.

  3. Interesting! I must say, I always learn something new all the time, doing this blog. When you said you had weak knees, but were physically active, I thought perhaps "weakness" was another way of saying "it feels like the knees are about to give way." But you say that's not the sensation. So I guess I can't quite figure out what the "weakness" would be, if your legs are strong and your knees feel fine other than being weak. But it sounds like you're making good progress, trying things on your own and troubleshooting, so congrats.