Articular cartilage defects in the knee are common, particularly among athletes. Because of the limited healing capacity of articular cartilage, left untreated, these defects are at risk for progression towards debilitating osteoarthritis. Many treatment options exist, however, choosing the right time for intervention and the most optimal treatment plan for each patient remains a challenge because the natural history of articular cartilage defects is not fully understood.

The purpose of this dissertation was to investigate measurable biomechanical factors that may be associated with articular cartilage degeneration in the knee as an early step toward improving patient care and preventing cartilage defect progression. My collaborators and I began with two foundational studies which laid the groundwork for our additional investigations. First, we determined the sensitivity of resultant joint kinematics to various calculation techniques in order to assist with the selection of appropriate data analysis protocols. Next, we explored joint moment symmetry in healthy adult populations during walking, which revealed a larger magnitude and prevalence of asymmetry than anticipated and provided a context for interpreting the results of additional investigations.

We then evaluated joint moments and intersegmental joint reaction forces in the knees of collegiate football linemen during sport-specific movement patterns in an effort to identify a possible contributor to the increased risk of cartilage injuries and degenerative joint diseases in football linemen. The magnitude of forces and moments produced during lineman-specific activities did not exceed those produced during walking or jogging;​ however, the deeper knee flexion angles at which they occurred may place unconditioned cartilage on the posterior femoral condyles at risk for damage.

We developed simplified finite element models of tibiofemoral contact to investigate the effects of bone geometry, meniscal deficiency, joint loading, defect size and their interactions on stress and subchondral bone contact which have been suggested as primary means of defect progression. We identified different sensitivities to bone geometry in our medial and lateral compartment models. Significant interaction effects suggest the benefit of considering multiple measurable parameters when assessing the risk of cartilage defect progression by stress and subchondral bone contact. Finally, we used motion capture and magnetic resonance imaging to determine the effects of a single season of collegiate football play, and subject-specific movement patterns, on articular cartilage health in the knees of asymptomatic football linemen. We identified cartilage abnormalities in 60% of our subjects at the preseason analysis and observed decreases in cartilage health in more than half of our subjects over a season of play. More years of collegiate football experience was a significant predictor of lower concentrations of glycosaminoglycan (GAG) at baseline. Greater vertical joint reaction forces during walking and greater frontal plane moments during li neman-specific movements were associated with higher preseason GAG concentration, but with a greater decrease in GAG concentration over the season of play. The results of this study provide additional evidence that cartilage may adapt to regular loading;​ however, the magnitude and repetition of loading that occurs during a season of football, and the likelihood of direct contact to the knee, may disrupt cartilage homeostasis and contribute to cartilage degeneration.

This dissertation advances our current understanding of factors which may influence cartilage defect progression and has identified potential predictive relationships between measurable subject-specific parameters and changes in cartilage health. The research presented here lays the groundwork for future investigations that will continue to expand our understanding of defect progression with the goal of assisting physicians with surgical decision-making and providing each patient with the most optimal treatment plan to restore joint function and prevent progressive degeneration.