Abnormal and cumulative loading in knee osteoarthritis

PURPOSE OF REVIEW: This review examines recent advances in understanding the abnormal mechanics characteristic of knee osteoarthritis and provides a rationale to assess the total exposure to knee loading during daily activity. RECENT FINDINGS: The abnormal loading environment in knee osteoarthritis is represented by the knee adduction moment. While knee osteoarthritis gait research focuses on this variable, emerging evidence supports a critical role for knee kinematics, muscle activation patterns and the kinematics and kinetics of other lower extremity joints in the development and progression of this disease. Nevertheless, abnormal knee loading is not the only cause of articular cartilage disruption. Excessive and repetitive loading, together creating a total exposure to loading, are critical factors in knee pathomechanics. To assess excessive and repetitive loading, cumulative load is a biomechanical approach that integrates loading exposures to represent the accumulated load that knee tissues endure during physical activity. SUMMARY: Knee osteoarthritis pathomechanics involves an interaction between abnormal and excessive and/or repetitive loading. Mechanics of lower extremity joints and muscle activation patterns influence the knee loading environment. Future work could integrate measures of abnormal loading with assessments of the total exposure to loading during physical activity to better link biomechanics with clinical outcomes in knee osteoarthritis.