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Knee & hip moments at push-off

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  • Knee & hip moments at push-off

    .. sharp intake of breath...

    I've spent quite a bit of time lately developing a nice multimedia tool for
    analysing gait. It does the full inverse dynamics analysis to derive joint
    moments and powers. I've been stuck lately on a discrepancy between the
    results using my system and the published results of David Winter. I've
    now, as we say in Australia, spat the dummy!

    I simply cannot see how Winter's group could get their curves for the
    normal knee and hip kinetics. Specifically, the joint (resultant) moments
    and powers during push-off (around 55% of cycle) peak at the following

    Moment Power
    Knee 0.85 Nm/kg extensor 4.8 W/kg eccentric
    Hip 1.35 Nm/kg flexor 1.45 W/kg concentric

    =46or comparison, Winter reports:

    Moment Power
    Knee 0.16 Nm/kg extensor 0.76 W/kg eccentric
    Hip 0.4 Nm/kg flexor 0.67 W/kg concentric

    I have found only one other set of normal curves, from Kabada's (1989)
    study, which I took from Dwight Meglans's chapter in "Human Walking". There
    are no powers quoted (Dwight seems to use Winter's data for these), and
    unfortunately his units are rather obscure, since he normalises for leg
    length (LL) as well as body weight:

    Knee 8 Nm/kg.LL extensor
    Hip 14 Nm/kg.LL flexor

    I don't know how to convert these values to Nm/kg, but scaling for the
    ankle moments (which all our results seem to agree on!) indicate dividing
    by a factor of about 10:

    Knee 0.8 Nm/kg extensor
    Hip 1.4 Nm/kg flexor

    i.e. the same as our results (and different from Winter's).

    Our results are quite repeatable - we so far have not examined anyone who
    gives curves like Winter's. At this point in time I still feel reluctant to
    criticise Winter, since his normal data is the gold standard. But since we
    seem to agree with Kabada, I now have the confidence to ask you all:


    What values are you getting?


    By the way, this experience has highlighted to me the need for more
    published data on normal joint kinetics. I even traced back through all the
    ISB proceedings and found very little except for Winter's reports. Does
    this mean that there's noone else doing joint kinetics? I'm sure there must

    I'll send a summary of responses.

    Many thanks,


    __________________________________________________ __________________
    Dr. Chris Kirtley MB ChB, PhD
    Lecturer, Bio-engineering --_ / \
    / \
    School of Physiotherapy, Perth #_.---._/
    Curtin University of Technology, V
    GPO Box U1987,
    Perth 6001, Tel +61 9 351 3649
    Western Australia. Fax +61 9 351 3636

    Internet Relay Chat: (port 6667) "bio-engineering"
    NetPhone: IP address 34311.180.105
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