Artificial cartilage

The smooth cartilage that covers the ends of long bones provides a level of lubrication that artificial alternatives haven't been able to rival – until now. Researchers say their lubricating layers of "molecular brushes" can outperform nature under the highest pressures encountered within joints, with potentially important implications for joint replacement surgery.

With every step we take, bones at the knee and hip rub against each other. That would quickly wear them away if it wasn't for the protection afforded by the thick layer of smooth and slippery cartilage that covers their ends.

No amount of polishing can remove all of the small imperfections from the stainless steel used in artificial joints. Any raised areas that are left grind against each other and release debris particles that soften the bone, explains Jacob Klein at the Weizmann Institute of Science in Rehovot, Israel.

Like bone, artificial joints must be covered with a cartilage-like layer. However, while it's possible to match cartilage's slick properties at low pressure, at the high pressures found in joints synthetic alternatives "seize up".