Obesity and Its Influence on Knee Joint Contact Forces in Individuals With Moderate Knee Osteoarthritis

Obesity is known as a major risk factor for the development and progression of knee OA. It has been proposed to affect the joint through linked mechanical and metabolic factors. However, its precise role in the pathomechanics of the disease is still not well understood. Given the importance of altered mechanical environment in both initiation and progression of knee OA, it is crucial to examine if and how obesity may affect the joint mechanically.

This thesis is a continuing work of our group on the role obesity and its influence on joint mechanics. Previous work in our group showed that obese individuals walk with altered pattern of knee joint loading and furthermore, obesity may expose the joint to higher absolute contact forces, found through an inverse dynamics model. Following the previous work by our group, in this thesis we used the method of principal component analysis to examine the role of obesity and its interaction with moderate knee OA on the neuromuscular patterns of major knee muscles. Our results showed that obese individuals walk with altered muscular activity, which was associated with delayed and prolonged activation of gastrocnemius muscles and sustained activation of the quadriceps muscles. This may result in sustained loading of the joint, proposed to be detrimental to joint integrity.

Following our first study on the neuromuscular patterns of major knee muscles, we implemented an electromyography driven model to incorporate the real EMG activity of knee muscles to estimate muscle forces and subsequently tibiofemoral joint contact forces. The model was validated against existing literature and then were calibrated for an asymptomatic obese and a healthy weight subject in order to find their medial, lateral, and total joint contact forces. This case study demonstrated the ability of the model to take into account the real activation patterns of the muscles in the estimation of muscle and knee joint contact forces. Furthermore, it was demonstrated the obese individual walked with higher absolute tibiofemoral joint contact forces compared to the healthy weight subject. This result will be further investigated by applying the model a large cohort with a range of BMI in the future.

Year	Entry
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Year

Entry

1996

Piazza SJ, Delp SL. The influence of muscles on knee flexion during the swing phase of gait. J Biomech. June 1996;29(6):723-733.

1998

Hurwitz DE, Sumner DR, Andriacchi TP, Sugar DA. Dynamic knee loads during gait predict proximal tibial bone distribution. J Biomech. May 1998;31(5):423-430.

1991

Schipplein OD, Andriacchi TP. Interaction between active and passive knee stabilizers during level walking. J Orthop Res. January 1991;9(1):113-119.

2003

Lloyd DG, Besier TF. An EMG-driven musculoskeletal model to estimate muscle forces and knee joint moments in vivo. J Biomech. June 2003;36(6):765-776.

2004

Buchanan TS, Lloyd DG, Manal K, Besier TF. Neuromusculoskeletal modeling: estimation of muscle forces and joint moments and movements from measurements of neural command. J Appl Biomech. November 2004;20(4):367-395.