Review of the SWIR Windows to Study Osteoarthritis.

Due to minimal absorption and scattering, light at select wavelengths in the short wavelength infrared (SWIR: 1000-2500 nm) region can be utilized for non-invasive, deep tissue imaging. These select wavelength regions, known as the SWIR windows, occur between 1200 and 1350 nm (second window), 1600 and 1870 nm (third), and 2100 and 2350 nm (fourth). The SWIR windows can penetrate deeply into tissue, revealing important information, such as collagen content. It is believed that osteoarthritis (OA), the most common form of arthritis, is due to the loss of proteoglycans and degradation of collagen-the main components of articular cartilage. In this paper, we review the SWIR windows for the detection and assessment of OA, an irreversible degenerative joint disease, based on changes in cartilage. With the use of longer SWIR wavelengths and artificial intelligence, the SWIR windows could open up new applications in the field of OA and bone diseases.