Friend or Foe? I know for many who suffer from knee pain that walking up, or even worse, walking DOWN, can be torture. The mere thought of descending stairs can bring you to tears. Through my decades of knee pain, knee surgeries, and knee recovery, I know it has for me.
For years I had managed to walk up stairs, up hills, up trails just fine. It was the downhill, down stairs, that caused the pain. So why is it that going down the hill or the stairs hurts? It has to do with the shear forces, body weight, and relationship of knee, hip, and ankle position and center of gravity.
It's not so much about how much your knee, hip, and ankle have to bend, but more about where your center of mass is relative to center of pressure. THAT has to do with where your weight bearing foot is relative to your body. As you climb stairs, your body weight presses into the weight bearing foot and that stays ahead of your body or just in line as you straighten your leg. By the time your foot is behind you (as you climb), you've already shifted your weight to the other foot ahead. When climbing stairs your quadriceps muscles are contracting (this is called a concentric contraction).
Here is an excerpt from one of my videos that shows a great "stair training" strength move. Start with a 4" or 6" step.
[video width="360" height="640" mp4="http://healthykneescoach.com/wp-content/uploads/2018/01/Down-the-Stairs-Move-2.mp4"][/video]
When going down stairs, you are resisting gravity. It's essentially a "controlled fall." Your quadriceps muscles are still working as they are lengthening, resisting release (this is called an eccentric contraction). The position of your foot while it is weight bearing shifts from in front of your body (and center of gravity) center of gravity to behind it before your other foot takes over (1), This makes the shear force in your knee greater (with the greater shift in body weight) and for those with Osteo Arthritis or issues with your patella, this can mean pain!
OF COURSE, if you are carrying extra weight, one of the best things you can do to reduce knee pain is to lose the extra pounds. The extra force in your knee going down stairs has been measured at 346% of your body weight (2). So if you carry an extra 25 lbs, that's an additional 85 lbs of force in your knee! WOW! Have you tried lifting up an 85 lb weight? It is HEAVY - so do your body a favor and drop the extra pounds. HINT: My Healthy Knees Cycling program can help you!
One of the major reasons I went ahead with my left knee replacement was because of mechanical issues while descending stairs. Not only pain, but an impingement in movement. That lead to compensation and my hip and back was beginning to bother me more and more. Being pretty stubborn, I did not want to resort to single leg descent for the rest of my life. A new knee was worth the risk.
Here we are, 10 weeks after my left knee replacement and 10 weeks of single leg stair descent (my right leg was thoroughly ready to share the load with my left) PLUS lots of practice with lowering my body (see the "stair descent move" video above)....
BOTH LEGS STAIR DESCENT AT LONG LAST! HOORAH!
(1) James E. Zachazewski, MS, PT, SCS, ATC ; Patrick O. Riley, PhD; David E. Krebs, PhD, PT; "Biomechanical analysis of body mass transfer during stair ascent and descent of healthy subjects", Journal of Rehabilitiation Research and Development, Vol. 30 No. 4 1993, pages 412-422, retrieved from https://pdfs.semanticscholar.org/304f/029c7ca21d2a4f4fce588bb3fc148ec20b72.pdf
(2) I. Kutzner, B. Heinlein, F. Graichen, A. Bender, Rohlmann, A. Halder, A. Beier, G. Bergmann; "Loading of the knee joint during activities of daily living measured in vivo in five subjects" Journal of Biomechanics 43 (2010) 2164-2173, retreived from https://pdfs.semanticscholar.org/537f/cac9d4b94cd54d989cbc690d18a4a02898fb.pdf
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