Do counteracting external frontal plane moments alter the intraarticular contact force distribution in the loaded human tibiofemoral joint?

• Simulated squats were carried out in a knee joint loading simulator in six cadavers.
• Externally applied counteracting frontal plane moments were experimentally varied.
• The medial compartment load increased during flexion in all investigated joints.
• Counteracting frontal plane moments redistribute intraarticular knee joint forces.
• Larger redistribution effects were found in higher knee flexion angles.

BackgroundThere 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.MethodsAdduction 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.ResultsExternally applied frontal plane moments altered the intraarticular force distribution and caused shifts in the centre of pressure up to 4.3 mm 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.ConclusionsThe 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 relevanceThe findings of this study offer novel insights to guide the development and optimization of mechanical aids for the treatment of osteoarthritic knees.