I'm trying to interpret some references that seem to give conflicting
information about dynamic quadriceps forces for knee movement as the
knee flexes from 0 to 90 degrees flexion, then extends back from 90 to 0
degrees. My reference is "Basic Biomechanics of the Musculoskeletal
System" (2nd ed.) by M. Nordin and V.H. Frankel. Fig. 6-19 (p. 129,
adapted from Lieb and Perry) shows the quads force increasing as the knee
extends, and decreasing as the knee flexes. Fig. 6-23 (p. 131, adapted
from Reilly and Martens) shows the quads force increasing as the knee
flexes to 90 degrees (deep knee bend). I assume that Lieb and Perry's data
is for standing upright and flexing the knee (I haven't been able to obtain
the original reference yet), while Reilly and Martens data is for the deep
knee bend. Ordinarily I think of the quads as extending the knee, but in
the deep knee bend, the moment arm to the center of gravity requires work
from the quads during flexion as well.

Would anyone care to comment on this, or suggest other sources of
(dynamic) quad force data during flexion-extension to shed
more light on this subject? I am particularly interested in *measured
quads and hams forces during flexion/extension for the deep knee bend*.

Please reply directly to me unless you think your response is of general
interest. Thank you.

Jenny Pavlovic pavl0009@gold.tc.umn.edu