Menisci, 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 football or tennis – can permanently damage these key supports, leading to pain and an increased risk of developing arthritis. Researchers have developed a hydrogel-based material that is the first to match human cartilage in strength and elasticity, while also remaining 3D-printable and stable inside the body. To demonstrate how it might work, the researchers used a $300 3D printer to create custom menisci for a plastic model of a knee.