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Technical FAQ: Leg-length discrepancies

  • By Lennard Zinn
  • Published May. 24, 2002
  • Updated Feb. 24, 2011 at 7:45 PM EST

Feedback on leg-length discrepancies

LZ, please excuse me if I am out of line with some advice on a previous question about leg length inequality back in April 25. I am a chiropractor as well as a triathlete and the team chiropractor for our local tri-team here in Dallas. I treat a lot of leg length inequalities in my office. The big question that must be asked is, is this functional or structural?

Unless Matt had a prior injury to say his femur and it was broken it could have very well healed with a slight difference from the opposite leg (structural). Otherwise, we must assume it’s functional. Meaning it changes with position or can be corrected with adjustments. Most leg length inequalities are a result of pelvic instability. The pelvis goes through many ranges of motion within normal daily activities, flaring out and in when sitting and walking (respectively), as well as rotating forward andbackward with normal gait. The problem arises when the SI (sacroiliac) joint gets fixated in any one position or combo of positions.

This actually moves the femur joint depending if the person is standing (weight bearing) or lying down. When standing, the feet are flat, so anx-ray will show the tops of the pelvis to be uneven, but when the personlies down the pelvis balances out and the inequality will show up in thefeet as one leg shorter. The bottom line is correcting the pelvic instability will correct the inequality. Correction comes from manual adjustments to the low back, and pelvis as well as strengthening the ligaments that supportand hold the SI joint in place.

Heel lifts can be used to help support the “short” leg until stabilizationcan be achieved. This is recommended over shimming the cleat or different crank arm lengths because when Matt is not on the bike he is unequal again(kind of like walking around with one shoe on and one shoe off). Correction must be constant, not just when he is on the bike in order for a change to be made within the spine/pelvis.
–Randy

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Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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