Increased varus frontal plane tibiofemoral alignment leads to a larger varus knee moment which increases the mechanical loading on the medial compartment of the knee. This increased loading may accelerate the initiation and progression of osteoarthritis (OA). The purpose of this study was to observe the effect of the frontal plane tibiofemoral alignment on the overall stress and strain within the knee joint during singleleg stance and the stance phase of the gait cycle. Motion analysis and

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... platform were used to obtain both kinetics and kinematics of the knee joint for three subjects with different frontal plane tibiofemoral knee alignment (varus, normal and valgus). Inverse dynamics and a muscle force reduction model were used to calculate the knee joint reactions. Subject specific 3-D knee models were created from MRI data. Finite element analysis (FEA) was performed to obtain the stress and strain at the knee joint. In addition, the combined effect of body weight changes and different amounts of lateral and medial meniscectomy on the contact stresses on the knee was investigated. FEA results showed the larger varus knee moment led to larger normalized maximum stress and strain at the medial compartment of the knee cartilage. The percentage of the total knee force distributed to the medial compartment of the knee during single-leg support increased for the varus aligned individual. Simulated body weight changes showed larger percentage increases in the stress and strain for a varus individual for all simulated increase in body weight. For similar amounts of partial lateral and medial meniscectomy, lateral meniscectomy led to greater increases in the stress and strain compared to medial meniscectomy due to the larger role of the relative load bearing of the lateral meniscus. Results from this study could be used by researchers and health care professionals to develop methods to prevent the initiation or slow the progression of knee OA. ii