cartilage of the knee wears out and no longer plays its role of shock absorber. In France, 80,000 to 90,000 knee prostheses are implanted each year. However, these metal prostheses have a limited lifespan (maximum 20 years) and often lead to a decrease in mobility. For several years, researchers have therefore been trying to develop hydrogels able to replace the joint. A difficult goal, because the gel must both be strong enough to bear body weight and flexible enough and slippery to serve as a shock absorber. It is precisely these qualities a priori opposites that researchers at Duke University in North Carolina (United States) have managed to combine. “data-reactid =” 12 “> Any sportsman knows: the knee is one of the most stressed joints of the body. Consider that each impact with the ground during the race, the stress exerted on the knee is equal to three to eight times the weight of the body! But after repeated trauma, overweight or age, cartilage of the knee wears out and no longer plays its role of shock absorber. In France, 80,000 to 90,000 knee prostheses are implanted each year. However, these metal prostheses have a limited lifespan (maximum 20 years) and often lead to a decrease in mobility. For several years, researchers have therefore been trying to develop hydrogels able to replace the joint. A difficult goal, because the gel must both be strong enough to bear body weight and flexible enough and slippery to serve as a shock absorber. It is precisely these qualities a priori opposites that researchers at Duke University in North Carolina (United States) have managed to combine.