Modes of in vivo cartilage recovery

Osteoarthritis is often suggested to occur through the progressive wear and tear of the articular cartilage. However, epidemiological studies have shown joint activity is a protective activity that decreases a person’s risk for developing osteoarthritis. Furthermore, one of the most effective therapies for treating and managing early osteoarthritis is mobilizing and loading the affected joint. We propose that mobilizing joints activates a recovery mechanism that restores in vivo cartilage mechanics.

In vivo imaging has shown that static joint loading (e.g., standing) leads to fluid exudation and cartilage thinning (up to 50% in 3 hours), while passive unloading (e.g., laying down) leads to fluid recovery and cartilage thickening. Given this, effective dosing of loading and unloading should be sufficient to maintain cartilage thickness and hydration. However, this raises the question of how loaded activities such as running, which can be sustained for many hours, are not damaging as they should dehydrate and substantially thin the cartilage. Magnetic resonance imaging of human joints has shown that during continuous activity the cartilage thins by ~5% but then plateaus, demonstrating that activity either maintains cartilage thickness and hydration or is capable of restoring and creating a dynamic equilibrium.

In this project you will investigate the potential of different types of joint activity (e.g., walking, running, squatting) to recover cartilage in vivo. In this project you will be exposed to human subjects research, the IRB process, magnetic resonance imaging at the CMU-Pitt BRIDGE Center, image analysis, and data analysis. The results of this work will help to guide our understanding of how transient activities may provide a protective effect against cartilage degeneration.