Tapping in on osteoarthritis

An atomic force microscope can detect signs of osteoarthritis long before existing diagnostic methods, according to a paper online this week in Nature Nanotechnology. The research, by Martin Stolz and colleagues, could lead to development of a minimally invasive arthroscopic tool for clinics, so that earlier treatments can be implemented.

Osteoarthritis, a debilitating degenerative joint disease prevalent among older people, starts at the molecular scale and progressively spreads to the higher architecture of the cartilage. Pain is caused by wearing down of the cartilage that cushions joints, and a decrease in the fluid that would usually keep them lubricated. At present, there are no known cures for the disease.

The atomic force microscope works by tapping the surface of a material with a sharp tip and recording the changes in the tip displacement ? which corresponds to stiffness. The cartilage in osteoarthritic mice and normal aging-mice is stiffer and has thicker cartilage fibres over time. Importantly, cartilage changes were seen as early as one month using nano-sized tips, whereas routine methods and micron-sized tips did not show any damage until six months. The method could also distinguish the different grades of cartilage obtained from patients undergoing hip or knee replacements.