A method of making prosthetic knee menisci to be implanted in place of deteriorated or damaged native menisci, said prosthetic menisci being internally reinforced and sequentially moulded in open form from a suitable biocompatible elastomeric polymer material, said prosthetic menisci subsequently being transformed into closed, hollow forms said hollow forms being sized for femoral and tibial condylar surfaces and filled or inflated after implantation by injection into them of a gel or settable polymer to shape them into congruence with the femoral and tibial condyles, the surfaces of said menisci being chemically and/or physically treated to improve the efficiency of lubrication by synovial fluid and to provide enhanced wear characteristics, and said prosthetic menisci being restricted in translation within the interarticular space by anchorage of their anterior and posterior horns to the tibia and by the provision of secondary locating elements.