Objective: Mechanical loading has been implicated in osteoarthritis but the relationships between the many components of joint loading in vivo and clinical progression of knee osteoarthritis has not been fully explored. The goal of this thesis was to better understand how features of the knee joint loading environment are related to clinical progression of medial tibiofemoral knee osteoarthritis.
Methods: Five studies were undertaken to address this goal. Using principal component analysis to extract patterns of variation in knee moment and electromyography waveforms, the first two studies explored differences in baseline gait features associated with structural and clinical osteoarthritis progression and the relative contributions of moment and electromyography data to discriminating between those who do or do not progress clinically at follow-up. The next two studies investigated factors influencing joint loading frequency using accelerometers. Last, correlations between joint loading magnitude/duration variables (from gait) and joint loading frequency (from accelerometers) were investigated and differences in these variables between individuals who do or do not progress clinically at follow-up were identified.
Results: The patterns of electromyography waveforms were important to clinical progression, and combining moment and electromyography features better discriminated clinical progression versus no progression than either alone. Differences in habitual joint loading frequency between groups were identified using a single week of accelerometer data but individual variations over a year were high. Differences in joint loading frequency were also found between women and men but depended on whether individuals had symptomatic or asymptomatic osteoarthritis. Gait, but not joint loading frequency, differences were present at baseline in those who progressed clinically at short-term follow-up but individuals with the lowest frequency levels exhibited gait patterns that have been linked to clinical progression.
Conclusions: Given the large burden of osteoarthritis on patients and the healthcare system, addressing patterns of prolonged muscle activation in those at risk of clinical progression may provide alternative treatment opportunities. While joint loading frequency was not related to clinical osteoarthritis progression over a short follow-up, the gait patterns seen in individuals with low frequency levels suggest that these individuals are especially in need of intervention.