Ward SR, Powers CM.
To determine if persons with patella alta exhibit elevated
patellofemoral joint stress compared to pain-free controls during normal and fast
Twenty-four subjects (13 patella alta, 11 pain-free controls)
Sagittal and axial magnetic resonance images of the knee were obtained
to quantify subject specific knee extensor mechanics and patellofemoral joint
contact area. Instrumented gait analysis was used to quantify knee joint
kinematics and kinetics. MRI and gait data were used as input variables into a
model of patellofemoral joint stress. Analysis of variance with repeated measures
was used to compare group differences and group x gait speed interactions for
each dependent variable during stance.
During normal speed gait there were no group differences in peak knee
flexion angle, knee extensor moment, joint reaction force, or stress. However,
the patella alta group had significantly less contact area. During fast speed
gait there were no group differences in peak knee flexion angle, knee extensor
moment, or joint reaction force. However, the patella alta group demonstrated
significantly less contact area and significantly greater stress compared to
Persons with patella alta demonstrated greater calculated
patellofemoral stress during fast walking. This was the result of reductions in
contact area as joint reaction forces were similar between groups.
Persons with patella alta may be predisposed to patellofemoral
dysfunction through elevations in joint stress. Therefore, treatments aimed at
increasing the load-bearing surface area between the patella and femur, such as
bracing, may be beneficial in this patient population.
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