Friday, April 10, 2009

The Inside Story on Knees


The theme in my classes this week is the knee joint, by itself and in relation to the foot and hip.  I've been contemplating the psychological correlate of the knee.  Our connection to our feet, for example, relates to how grounded we feel in our lives.  But what about knees?  There is something elusive about the knee - it doesn't "feel" much of anything except when it suddenly starts hurting.   It's an intermediary, the site of transition between sitting and standing and walking.  It's rare that we even notice them.

Yoga is fairly obsessed with the knee, especially keeping it in alignment over the foot, and keeping it supported with muscle rather than hanging into ligament.  Most alignment cues in yoga class refer to external landmarks - usually the knee cap tracking down the center line of the foot.  But I think it is useful to learn to align the knee from within.  

The knee doesn't have many nerves within the joint itself, but it is possible to feel a subtle sense of pressure where the end of the thigh bone (femur) meets the top of the shin bone (tibia).  The femur ends in two rounded knobs that roll over the top of the tibia, somewhat like a rocking chair.  When weight travels through the knee joint, it can therefore rest more to the inside or outside of the knee joint.  You can tune into this internal structure by coming into a lunge position and gentle rocking your front knee back and forth, moving weight between inner heel and outer heel.   Focus on the feeling in the knee, a sense of pressure moving between inner knee and outer knee.  Try to keep the sensation in the joint, not pressing into sharper sensation that come from the tendons stretching across the outside of the joint.

The more you can feel when weight is centered in your knee, the less you'll need to look at the knee when you enter a weight-bearing pose such as Warrior 2.  In Triangle, you can fine tune your muscular effort to guide pressure through the center of the knee rather than sagging into the tendons on the back of the knee.  And outside of yoga, this increased sensitivity will help you walk and run in a more knee-friendly way.  I've found working on an elliptical machine, with feet fixed in the foot pads, is a really useful way to practice tracking the knees symmetrically.

Of course, the alignment of the knees is only part of the picture.  Forcing the knees into a different position without also adjusting the action in the feet and hips may create more strain than before.

1 comment:

  1. Consider that the weight may never travel through the knee joint. The condoils (the rounded knobs) are the attachment points for various knee ligaments; those ligaments keep the femur and tibia separate. One subtlety about the anatomy: the condoils cause the two bones to overlap when viewing sideways; that's what allows the tension of the knee ligaments to hold the bones apart.

    Dr. Stephen Levin (biotensegrity.com) was an orthopedic surgeon. He repeatedly attempted to cause these two bones to touch and could never do that. He has several papers on his website explaining why a compression-based model cannot work our musculoskeletal anatomy. Levin explains the alternative: that the loads are carried tensionally, a model called a floating compression or tensegrity structure.

    Myers maps out this tensional structure in his text "Anatomy Trains". The second edition of his book came out earlier this year; a 20-page PDF summary of the first edition is available on his webpage anatomytrains.com .

    A third site to explore is modelmaker Tom Flemons's site www.intensiondesigns.com . Collaborating with Levin, Flemons makes medical-grade functional models of our musculoskeletal system. Flemons published a great paper about the knee joint about a year ago on his website.

    None of this invalidates your advice. Alignment is crucial to moving in a knee-friendly manner, and the position of the whole foot-knee-hip system is crucial to moving in an effortless fashion.

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