Importance of preswing rectus femoris activity in stiff-knee gait.
ABSTRACT Stiff-knee gait is characterized by diminished and delayed knee flexion during swing. Rectus femoris transfer surgery, a common treatment for stiff-knee gait, is often recommended when a patient exhibits prolonged activity of the rectus femoris muscle during swing. Treatment outcomes are inconsistent, in part, due to limited understanding of the biomechanical factors contributing to stiff-knee gait. This study used a combination of gait analysis and dynamic simulation to examine how activity of the rectus femoris during swing, and prior to swing, contribute to knee flexion. A group of muscle-actuated dynamic simulations was created that accurately reproduced the gait dynamics of ten subjects with stiff-knee gait. These simulations were used to examine the effects of rectus femoris activity on knee motion by eliminating rectus femoris activity during preswing and separately during early swing. The increase in peak knee flexion by eliminating rectus femoris activity during preswing (7.5+/-3.1 degrees ) was significantly greater on average (paired t-test, p=0.035) than during early swing (4.7+/-3.6 degrees ). These results suggest that preswing rectus femoris activity is at least as influential as early swing activity in limiting the knee flexion of persons with stiff-knee gait. In evaluating rectus femoris activity for treatment of stiff-knee gait, preswing as well as early swing activity should be examined.
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ABSTRACT: Although the movement of the leg during swing phase is often compared to the unforced motion of a compound pendulum, the muscles of the leg are active during swing and presumably influence its motion. To examine the roles of muscles in determining swing phase knee flexion, we developed a muscle-actuated forward dynamic simulation of the swing phase of normal gait. Joint angles and angular velocities at toe-off were derived from experimental measurements, as were pelvis motions and muscle excitations. Joint angles and joint moments resulting from the simulation corresponded to experimental measurements made during normal gait. Muscular joint moments and initial joint angular velocities were altered to determine the effects of each upon peak knee flexion in swing phase. As expected, the simulation demonstrated that either increasing knee extension moment or decreasing toe-off knee flexion velocity decreased peak knee flexion. Decreasing hip flexion moment or increasing toe-off hip flexion velocity also caused substantial decreases in peak knee flexion. The rectus femoris muscle played an important role in regulating knee flexion; removal of the rectus femoris actuator from the model resulted in hyperflexion of the knee, whereas an increase in the excitation input to the rectus femoris actuator reduced knee flexion. These findings confirm that reduced knee flexion during the swing phase (stiff-knee gait) may be caused by overactivity of the rectus femoris. The simulations also suggest that weakened hip flexors and stance phase factors that determine the angular velocities of the knee and hip at toe-off may be responsible for decreased knee flexion during swing phase.Journal of Biomechanics 07/1996; 29(6):723-33. · 2.72 Impact Factor
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ABSTRACT: To evaluate the outcome of hamstring lengthening and distal rectus femoris transfer, a retrospective study was performed comparing preoperative and postoperative gait analysis data from 16 children with neurologic involvement. Postoperatively, the timing of peak knee flexion during swing and the total arc of knee motion significantly improved. Hamstring range of motion and knee extension at terminal swing significantly improved, but stride length and gait velocity did not for the overall population. Patients who used braces postoperatively showed an improvement in stride length and velocity when wearing orthoses. This suggests that postoperative bracing may be needed in some patients to maximize the surgical outcome.Journal of Pediatric Orthopaedics B 05/1999; 8(2):75-9. · 0.53 Impact Factor
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ABSTRACT: A mathematical representation of the human leg during the swing phase of gait was developed. The modelling procedure employed variables which were known to be clinically significant physical, anatomical and physiological features influencing the gait pattern. These included: limitations in joint range of motion, alterations in the initial conditions of swing, changes in joint trajectories and changes in the inertial properties of the limb segments. The model implemented was such that these parameters could be independently varied to assess their relative importance in either normal gait, or in pathological gait and its correction. Using this approach, quantitative clinical data was incorporated into the mathematical description so that a better understanding of normal and pathological gait could be achieved.Journal of Biomechanics 02/1981; 14(12):823-32. · 2.72 Impact Factor
IMPORTANCE OF PRESWING RECTUS FEMORIS ACTIVITY
IN STIFF-KNEE GAIT
Melanie D. Fox1, Jeffrey A. Reinbolt2, Allison S. Arnold1, Silvia Õunpuu3 and Scott L. Delp1,2
Departments of Mechanical Engineering1 and Bioengineering2, Stanford University
Center for Motion Analysis, Connecticut Children’s Medical Center3
Email: firstname.lastname@example.org Web: http://www.stanford.edu/group/nmbl/
Stiff-knee gait, a common pathological
walking pattern of persons with cerebral
palsy, is characterized by reduced and
delayed peak knee flexion during the swing
phase of gait. This abnormality may lead to
tripping or energy-inefficient compensatory
movements due to inadequate toe clearance
(Sutherland and Davids, 1993). The
reduction in knee flexion has commonly
been attributed to over-activity of the rectus
femoris during swing phase (Perry, 1987).
However, abnormal muscle activity during
the stance phase, such as excessive force in
vasti or rectus femoris, may decrease knee
flexion velocity at toe off and limit knee
flexion in swing (Goldberg et al., 2006).
Rectus femoris transfer surgery, which is
intended to decrease the muscle’s knee
extension moment while preserving its hip
flexion moment, is a common treatment for
stiff-knee gait. It is generally indicated
when a patient exhibits abnormal rectus
femoris excitation during swing phase.
However, if stance phase factors also inhibit
knee flexion, excessive excitation of rectus
femoris during preswing may also be an
important indication for rectus femoris
transfer surgery. The purpose of this study
was to evaluate the relative importance of
preswing rectus femoris activity to peak
knee flexion in patients with stiff knee gait.
We assessed the effects of rectus femoris
activity during stance and swing by creating
dynamic gait simulations of ten patients with
cerebral palsy. These subjects, with an
average age of 10.6 years, were each
categorized as exhibiting stiff-knee gait in at
least one limb by Goldberg et al. (2006).
The gait analysis data were collected at
Connecticut Children’s Medical Center in
Hartford, CT, as a routine part of treatment
planning. No subject exhibited excessive
knee extension moments or diminished hip
flexion moments during swing (Goldberg et
al., 2006). Most subjects displayed
excessive knee extension moments during
double support. A musculoskeletal model
with 21 degrees-of-freedom and 92 muscle
actuators was scaled to represent the size of
each subject. Using computed muscle
control (Thelen et al., 2003) we determined
a set of muscle excitation patterns for each
subject that produced kinematics similar to
the subject’s measured motions when used
to drive a forward dynamic simulation. The
computed excitation patterns were generally
consistent with each subject’s measured
EMG data. Forward dynamic simulations
were performed for the period of preswing
through peak knee flexion.
To investigate the relative contribution of
rectus femoris activity during preswing and
swing on knee flexion, two more
simulations were created for each patient;
one in which rectus femoris excitation was
eliminated during preswing only, and a
second in which rectus femoris excitation
was eliminated during swing only (Fig. 1).
Preswing was defined to be a time period
before toe-off equal in length to early swing.
Early swing was defined to be the period of
gait from toe-off to peak knee flexion. The
difference in amount of peak knee flexion
Gait Cycle (%)
Knee Flexion (o)
RF excitation eliminated in preswing
RF excitation eliminated in swing
Figure 1: Simulated knee flexion angles
when rectus femoris excitation was
eliminated during different phases. Shaded
region represents normal knee flexion ± 2
improvement between the two cases was
compared for each patient.
RESULTS AND DISCUSSION
Simulated improvement in peak knee
flexion when rectus femoris excitations were
eliminated during preswing was greater than
that when rectus femoris excitations were
eliminated during early swing in eight out of
ten subjects. Using a paired t-test (p<0.05),
the amount of peak knee flexion
improvement attained by eliminating rectus
femoris excitations during preswing was
significantly greater than the amount of peak
knee flexion improvement attained by
eliminating rectus femoris excitations during
swing (Fig. 2). This result suggests that
rectus femoris activity during preswing may
have greater influence on peak knee flexion
than rectus femoris activity during early
swing in some patients with stiff-knee gait.
In evaluating the causes of stiff-knee gait,
one should examine rectus femoris EMG in
preswing as well as early swing (before peak
flexion is attained) for abnormal activity.
Dynamic simulations allow one to evaluate
the changes in body motions caused by
Figure 2: Average simulated improvement
in peak knee flexion among all 10 subjects
when rectus femoris excitation was
eliminated in preswing or swing. Error bars
signify ± 1 SD.
alterations in the timing of muscle activity.
This provides a valuable tool for assessing
and investigating the mechanisms leading to
improvements in some patients following
treatment for stiff knee gait. Our future
work will focus on simulating the
postoperative gait of subjects with good and
poor surgical outcomes to determine why
some subjects have a dramatic improvement
with treatment while others improve very
little or get worse.
Goldberg, S. et al. (2006). J Biomech, 39, 689-
Perry, J. (1987). Dev Med Child Neurol, 29,
Sutherland, D.H., Davids, J.R. (1993). Clin
Orthop Relat Res, 288, 139-147.
Thelen, D.G. et al. (2003). J Biomech, 36, 321-
The authors thank the staff of the Center for
Motion Analysis at the Connecticut
Children’s Medical Center. This research
was funded by the NSF, NIH R01
HD046814, and NIH Roadmap for Medical
Research U54 GM072970.
Simulated Improvement in Peak Knee Flexion (°)