Observing dynamic changes in articular cartilage birefringence during compression using polarization-sensitive optical coherence tomography

Destructuring of the extracellular matrix has been identified as a key factor in the initial stages of cartilage degeneration. The disruption and reorganisation of the collagen network leads to alterations in the materials intrinsic birefringent properties. A recent study showed that healthy bovine cartilage, that has been compressed and fixed, exhibits stronger birefringence than cartilage with early signs of degeneration. In this summary, we use polarization-sensitive optical coherence tomography (PS-OCT) to dynamically extract such optical properties, in real-time, during an established creep loading protocol. Preliminary results provide an insight into the physiological response of collagen fibers which indicate that the observed birefringence is likely due to the middle and deep zone fiber alignment becoming non-parallel with respect to the propagating light. This finding not only helps explain many of the contradictory findings presented in previous studies but also demonstrates that PS-OCT offers a non-destructive and non-invasive method to gain insight into the complex physiology behind cartilage degeneration in a real-time manner.