Using a goniometer to measure knee angle

[tctrek]

I recently had a VO2MAX test done by a local cycling coach using my bike on his trainer. He mentioned that I was probably losing power because the angle of my knee on the downstroke was 48% and 40% was optimal. So, on yesterdays ride I raised my seat by about an inch. I definitely felt more power especially on the seated climbs. But about halfway through the ride I had a little nagging pain behind my right knee on every downstroke. If I concentrated on mostly pulling up, the pain went away.

I'm thinking I may have my seat a little too high now, but I'd really like to know for sure. I think a goniometer will tell me what I want to know and I would like to have one to regularly check that my angle is correct because I think my seat tends to slide down over time/road conditions, etc.

Can anyone recommend a size/brand of goniometer? There's a million of them on Amazon.com and it's confusing.

[Presto]

I don't mean to burst your bubble, but honestly there is nothing magical about a goniometer. It just gets you into the general neighborhood, and then you do the fine tuning by feel.

If your saddle feels too high, lower it a 1/8 inch or so at a time until it feels better and you still have that increased sense of power. Your saddle may end up in a position that puts your knee at 37 degrees or 43 degrees or even 40 degrees, it doesn't matter as long as you feel good and strong.

Put a mark on your seat post when you find the height that feels right. Then if it slips down, you know where to set it again.

[OakLeaf]

I don't have any input on the goniometer (other than I really doubt it's something you can use accurately by yourself), but you definitely don't want to move your saddle that much all at once. Two or three millimeters at a time, let your body adjust over a couple of hundred miles minimum, then move it some more if you want.

[tctrek]

I don't mean to burst your bubble, but honestly there is nothing magical about a goniometer. .

Sure, I get that. It's just that I rode my bike for at least 6 months with the seat too low and absolutely no pain on my knees, etc. but an apparent loss of power that I did not realize was happening.

I can go by feel, but wanted to get a little closer to optimum 'cause I need all the help I can get climbing . My DH would help me to measure the angle on my trainer. There are many goniometers online that are quite inexpensive (under $10), so I thought it would be good to have one.

[Presto]

I can go by feel, but wanted to get a little closer to optimum 'cause I need all the help I can get climbing .

"Feel" is optimum. One person's optimum is another person's agony. Fred's optimum might be 37 degrees for max output, while Fredwina's optimum might be 43 degrees for max output. (pain decreases output, too) If I set either at 40 degrees and told them it was perfect, they'd be back at the shop in a week and unhappy with me.

The most important goniometric measurement was the one you had with the coach, which showed your current angle well outside the 35-45 degree range. You raised your saddle, and felt the good power change. You needed to raise the saddle and you felt the improvement when you did. Now you just need to fiddle with it so you aren't irritating your knee. Where your saddle actually ends up is determined by your unique body.

Trust yourself. You can do this!

[Presto]

This is the goniometer I use. http://www.frenchcreekmedical.com/pr...p/do-gon12.htm

Make sure you line it up with the correct bony landmarks. (lateral malleolus and greater trochanter) Center the axis of the goni on the axis of the knee joint itself. Remember that the patella is not part of the axis. Make sure your ankle is in its comfortable position. Changing the flex of your ankle will completely change your knee angle, so watch it. Keep your hips level during measuring.

Even highly trained people can vary in their measurements by 5 degrees, so take any number you get with a 5 degree grain of salt.

Then fine tune it by feel. Trust yourself, really!

[tctrek]

Thanks for the advice. That makes perfect sense. I guess being in IT that I'm too much of a math geek and always looking for the algorithm/logic that works!

[Tokie]

We use a piece of electrical tape wrapped around the seatpost for a starting point. A tiny change in seat height can be very significant -(as you just found out) - go slow! Tokie