Relationships Among Knee Loads During Gait and C-Reactive Protein In Knee Osteoarthritis: A Preliminary Study

Abstract

Knee osteoarthritis (OA) is associated with biomechanical and physiological factors including lower extremity joint moments and knee joint forces during gait and inflammatory markers such as C-reactive protein (CRP) supporting the existence of both biomechanical and physiological pathways to disease progression and possibly amelioration. Little is know however about the relationships among these pathways. PURPOSE: To identify the relationships among anthropometric measures of body weight and BMI, gait biomechanical measures of knee joint abductor moment and compressive force, and the inflammatory marker CRP in older adults with knee OA. METHODS: Data were obtained from a subset of 210 older adults (age: 66 yrs, mass: 93 kg, BMI: 33 kg/m2) out of 450 participants having radiographically diagnosed knee OA enrolled in the Intensive Dietary Restriction with Exercise in Arthritis (IDEA) trial. 3D inverse dynamics analysis of the lower extremity was used to calculate knee abductor moment and compressive force during level walking. Serum levels of CRP were determined using an automated immunoanalyzer and were log-transformed for analyses. Pearson product moment correlations among these variables were calculated to identify the relationships among the biomechanical and physiological variables (p<0.05). RESULTS: Knee joint compressive force was relatively strongly related to body mass (r=0.65) and walking speed (r=0.48) and moderately related to BMI (r=0.27) and peak knee abductor moment (r=0.17). CRP was moderately related to BMI (r=0.22) but had statistically non-significant relationships with knee compressive force (r=0.03) and peak knee moment (r=-0.09). CONCLUSIONS: The data showed a surprisingly minimal relationship between established biomechanical and physiological pathways associated with knee OA. The moderate-strength relationships between BMI and both biomechanical (knee compressive force) and physiological (CRP) variables suggest a possible, if only tenuous, connection between the two pathways. Our data are limited to a single measure of inflammation and it is possible other pro-inflammatory cytokines including interleukin 6 or tumor necrosis factor-alpha may show a stronger connection between biomechanical and physiological pathways in knee OA. Supported by NIH R01 AR052528.