 Poster: A snowHead
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I am always being to told off for using too much knee angulation and that it is bad for my knees. I would like to understand exactly what is involved, because I have never been convinced that the knee is being bent in an unnatural direction.
Experimentation (without ski boots on) suggests that it involves rotating the foot at the ankle. For example, if I get myself in to a position where my outside leg has some knee angulation, then I can eliminate it (while keeping my hip, knee and heel in fixed positions) by pointing my toes further inwards -- pointing my toes outwards increases knee angulation again. (Obviously ankle flex and fore-aft balance also change as I do this...)
Clearly one has far less ankle movement when wearing ski boots. But, is knee angulation when skiing just a matter of driving the knee inwards so that the toes are left pointing outwards, with the ankle having to rotate as a result? If so then I guess too much knee angulation will cause the lower leg to exert a twisting force on the knee. Is this what causes the damage?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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FastMan wrote:
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The primary mechanism for creating knee angulation is inward rotation of the femur in the hip socket. The knee has little ability to flex sideways. By rotating the femur inward, normal knee flex can appear to angulate the knee.
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This sounds a bit like what I was thinking - that knee angulation is knee flex which does not line up properly with the ski.
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Imagine trying to bear the load of dynamic turn forces with the leg in the contorted position above. The risk of injury is greater, because jarring forces impact misaligned ligaments and joints.
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So you would reject the following hypothesis?: It is impossible to generate knee angulation without, as a by-product, getting ankle twisting to accomodate it.
It still seems to me that any misalignment/contortion is caused by the tibia and fibula twisting around each other rather than from the knee bending sideways.
Another experiment. Sit on the floor with your knees and ankles bent at right-angles and your heels touching the floor. Keeping your bum, right knee and right heel in fixed positions, reach down and rotate the toes of your right root to the right. Ignoring the what happens in the hip and above, I think this is an example of the position your leg can get in to when it has knee angulation. Do you disagree? Certainly only a limited amout of twisting of the foot is possible (before something goes pop), and it does make the knee feel somewhat stressed.
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| rmdkrk wrote: |
This sounds a bit like what I was thinking - that knee angulation is knee flex which does not line up properly with the ski.
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Well put.
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| So you would reject the following hypothesis?: It is impossible to generate knee angulation without, as a by-product, getting ankle twisting to accomodate it. |
Nope, don't reject that at all. Articulation and adaptation has to happen at both ends of the leg.
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| It still seems to me that any misalignment/contortion is caused by the tibia and fibula twisting around each other rather than from the knee bending sideways. |
Agree on this too. This points to the "misalignment" I was referring to. We're creating knee angluation, via a rotation of the femur in the hip socket, while keeping the foot still pointing forward. It twists the lower leg, in relation to the direction of flex, just like you say. The lower leg doesn't like that. It introduces extra stress on the ligaments and tendons.
Try doing knee angulation by rotating the femur, and allowing the foot to rotate with it. Now flex. The knee, lower leg, and ankle like it much better. Unfortunately, such a position doesn't work very well when skiing.
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