By Jordana Bieze Foster
Knee osteoarthritis researchers are taking a closer look at the factors that influence knee adduction moment (KAM) and also considering the contributions of sagittal plane variables, as illustrated by studies presented in September at the American Society of Biomechanics (ASB) annual meeting in Omaha, NE.
The knee-ground reaction force (GRF) lever arm is a stronger predictor of KAM after arthroscopic partial meniscectomy (APM) than frontal plane GRF magnitude and therefore might be a desirable focus for interventions to prevent or delay the development of knee osteoarthritis in these patients, according to research from the University of Melbourne in Australia.
Investigators performed a secondary analysis of gait data from an earlier study in which 65 individuals with isolated medial APM demonstrated a statistically significant 9% increase in KAM two years after surgery. The secondary analysis revealed that the two-year change from baseline of the knee-GRF lever arm, calculated as the perpendicular distance between the frontal plane GRF vector and knee joint center of rotation, accounted for 29% of the variance in KAM increase. The change in frontal plane GRF magnitude accounted for 14% of the variance.
“We might have more of a chance to decrease knee adduction moment if we can decrease the lever arm,” said Michelle Hall, a graduate student in the Sports Medicine Research Program at the University of Melbourne, who presented her group’s findings at the ASB meeting.
Although the majority of knee osteoarthritis studies use KAM as a surrogate marker for knee loading, a study from Stanford University in Stanford, CA, suggests that knee flexion moment could also be a clinically important marker for osteoarthritis progression.
Researchers analyzed the gait of 18 female patients with medial tibiofemoral compartment knee osteoarthritis (mean Kellgren-Lawrence grade of 2.3) at baseline; they also obtained magnetic resonance (MR) images of the affected knees at baseline and after five years.
They found that baseline knee flexion moment significantly predicted changes in medial tibial cartilage at five years, whereas baseline knee adduction moment did not.
“Knee adduction moment and knee flexion moment really should both be considered in patients with medial compartment knee osteoarthritis,” said Eric F. Chehab, a graduate student in the department of bioengineering at Stanford, who presented the findings at the ASB meeting.
Sagittal plane variables may also influence the effect of lateral wedging in patients with medial knee osteoarthritis, according to research from the Kessler Foundation Research Center in West Orange, NJ.
Investigators took weight-bearing MR images of the knee in 12 individuals with medial tibiofemoral knee osteoarthritis wearing custom shoes with external nylon heel wedges that could be rotated to provide 0° or 5° of lateral wedging.
At 20° of knee flexion, the wedge condition was associated with an anterior migration of the lateral compartment that approached significance when compared to the no-wedge condition; the same effect was not seen at 0° of flexion.
“Because ankle dorsiflexion accompanies knee flexion, that decrease in ankle mobility may have increased transmission of forces upward,” said Peter J. Barrance, PhD, an assistant professor in the Department of Physical Medicine & Rehabilitation at Rutgers New Jersey Medical School in Newark, who presented the findings at the ASB meeting.
Study participants were not screened for foot type or other variables associated with responsiveness to lateral wedging, which may have contributed to the variability and the lack of statistical significance in the results, Barrance noted.
Hall M, Wrigley TV, Metcalf BR, et al. A longitudinal study of the knee adduction moment components post-arthroscopic partial meniscectomy. Presented at the American Society of Biomechanics 2013 Annual Meeting, Omaha, NE, September 2013.
Hall M, Wrigley TV, Metcalf BR, et al. A longitudinal study of strength and gait following arthroscopic partial meniscectomy. Med Sci Sports Exerc 2013 Jun 22. [Epub ahead of print]
Chehab EF, Favre J, Erhart-Hledik JC, Andriacchi TP. Knee flexion moment during walking influences medial compartment cartilage thickness in patients with knee osteoarthritis. Presented at the American Society of Biomechanics 2013 Annual Meeting, Omaha, NE, September 2013.
Barrance PJ, Gade V, Allen J, Cole JL. Tibiofemoral contact location changes associated with lateral heel wedging – a study using weightbearing MRI. Presented at the American Society of Biomechanics 2013 Annual Meeting, Omaha, NE, September 2013.