1. Prostheses of knee joint meniscuses implanted in place of worn-out native menisci in order to prevent damage to the articular cartilage of the femoral and tibial condyles and, as a consequence, to stop the progressive development of osteoarthritis Meniscus prostheses are made hollow, and they are filled with a curable polymer by injection to make them congruent with the surfaces of the femoral and tibial condyles while prostheses of the meniscus are made to the size corresponding to the surfaces of the femoral and tibial condyles have internal reinforcement to ensure strength and durability are made of a material having elastomeric characteristics that are similar to those of native menisci have supporting surfaces treated with chemical and (or) mechanical means, to improve the efficiency of lubrication with synovial fluid and wear-resistant characteristics of supporting surfaces and are limited in movement within the interarticular space by anchoring their anterior and posterior horns and by creating secondary fixation elements. Prostheses of the knee joint meniscus of claim 1, wherein the ends of the anterior and posterior horns include fixation plates made of a suitable metal alloy, the fixation plates fixed in place at the fixation points of the native menisci by suitable fastening devices extending through the fixation plates into the proximal the surfaces of the tibia, while the indentations are made, if necessary, in the proximal surfaces of the tibia and are limited in movement within the interarticular space by anchoring their anterior and posterior horns and by creating secondary fixation elements. Prostheses of the knee joint meniscus of claim 1, wherein the ends of the anterior and posterior horns include fixation plates made of a suitable metal alloy, the fixation plates fixed in place at the fixation points of the native menisci by suitable fastening devices extending through the fixation plates into the proximal the surfaces of the tibia, while t
