Background: There are strong indications that asymmetric medio-lateral load distribution in the knee joint is a risk factor for osteoarthritis. Externally applied frontal plane moments (adduction and abduction) might affect the distribution of knee joint compartment loading. However, this is not confirmed through intraarticular measurements in loaded human knee joints. The purpose of the study was to determine the force distribution and the movement of the centre of pressure in the loaded tibiofemoral joint as a function of varied externally applied counteracting frontal plane moments and in dependence of the knee flexion angle.
Methods: Adduction and abduction moments of 2.5 Nm and 5 Nm were applied to six cadaveric knees exhibiting varus, valgus and normal alignments. The joints were mounted in a knee joint loading simulator. During simulated muscle-driven extension-flexion cycles, intraarticular forces were determined using capacitive pressure sensors inserted into the medial and lateral knee joint compartments. Motion of femur and tibia were assessed by a motion analysis system.
Results: Externally applied frontal plane moments altered the intraarticular force distribution and caused shifts in the centre of pressure up to 4.3mm in all knee joints. Larger redistribution effects were found in higher knee flexion angles. The medial compartment load increased during the flexion in all investigated knee joints.
Conclusions: The application of counteracting frontal plane moments for the conservative treatment of osteoarthritis can redistribute the forces and might slow down the progression of the disease.
Clinical relevance: The findings of this study offer novel insights to guide the development and optimization of mechanical aids for the treatment of osteoarthritic knees.
Keywords: Intraarticular knee joint force; Knee adduction moment; Osteoarthritis; Valgus deformity; Varus.
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