PUBLISHED IN RESEARCH – By KARA MANKE
A cartilage-mimicking material created by researchers at Duke University may one day allow surgeons to 3-D print replacement knee parts that are custom-shaped to each patient’s anatomy.
Human knees come with a pair of built-in shock absorbers called the menisci. These ear-shaped hunks of cartilage, nestled between the thigh and shin bones, cushion every step we take. But a lifetime of wear-and-tear — or a single wrong step during a game of soccer or tennis — can permanently damage these key supports, leading to pain and an increased risk of developing arthritis. 
The hydrogel-based material the researchers developed is the first to match human cartilage in strength and elasticity while also remaining 3-D-printable and stable inside the body. To demonstrate how it might work, the researchers used a $300 3-D printer to create custom menisci for a plastic model of a knee.
“We’ve made it very easy now for anyone to print something that is pretty close in its mechanical properties to cartilage, in a relatively simple and inexpensive process,” said Benjamin Wiley, an associate professor of chemistry at Duke and author on the paper, which appears online in ACS Biomaterials Science and Engineering.
After we reach adulthood, the meniscus has limited ability to heal on its own. Surgeons can attempt to repair a torn or damaged meniscus, but often it must be partially or completely removed. Available implants either do not match the strength and elasticity of the original cartilage, or are not biocompatible, meaning they do not support the growth of cells to encourage healing around the site.
Recently, materials called hydrogels have been gaining traction as a replacement for lost cartilage. Hydrogels are biocompatible and share a very similar molecular structure to cartilage: if you zoom in on either, you’ll find a web of long string-like molecules with water molecules wedged into the gaps.