Influences of alignment and obesity on knee joint loading in osteoarthritic gait

Objective: To determine the influences of frontal plane knee alignment and obesity on knee joint loads in older, overweight and obese adults with knee osteoarthritis (OA). Methods: Cross-sectional investigation of alignment and obesity on knee joint loads using community dwelling older adults (age >= 55 years; 27 kg m(-2) >= body mass or body mass index (BMI) <= 41 kg m(-2); 69% female) with radiographic knee OA that were a subset of participants (157 out of 454) enrolled in the Intensive Diet and Exercise for Arthritis (IDEA) clinical trial. Results: A higher BMI was associated with greater (P = 0.0006) peak knee compressive forces [overweight, 2411 N (2182, 2639), class 1 obesity, 2772 N (2602, 2943), class 2+ obesity, 2993 N (2796, 3190)] and greater (P = 0.004) shear forces [overweight, 369 N (322, 415), class 1 obesity, 418 N (384, 453), class 2+ obesity, 472 N (432, 513)], independent of alignment, and varus alignment was associated (P < 0.0001) with greater peak external knee adduction moments, independent of BMI [valgus, 18.7 Nm (15.1, 22.4), neutral, 27.7 Nm (24.0, 31.4), varus, 37.0 Nm (34.4, 39.7)]. Conclusion: BMI and alignment were associated with different joint loading measures; alignment was more closely associated with the asymmetry or imbalance of loads across the medial and lateral knee compartments as reflected by the frontal plane external adduction moment, while BMI was associated with the magnitude of total tibiofemoral force. These data may be useful in selecting treatment options for knee OA patients (e.g., diet to reduce compressive loads or bracing to change alignment). (C) 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.