A persistent squeak led to the development of one of the most important medical technologies of the 1900s. In the early 1950s, John Charnley, an orthopaedic surgeon from Manchester, examined a patient who had been fitted with a replacement hip made from acrylic plastic. The acrylic hip squeaked so loudly that the man's wife would avoid being in the same room with him if at all possible.

Charnley spent many hours in the laboratory trying to reduce the friction between the hip replacement and the hip joint. After several failures he designed a two-component hip replacement made of metal and plastic. The metal part, or femoral component, was placed in the femur, which was hollowed out during surgery. The plastic part, called the acetabular cup, was cemented into the pelvis. The two parts combined to make a similar joint to a natural one. Charnley's prosthesis was copied and forms the basis of many modern designs, which is why he has earned a reputation as the ‘father of hip replacement’.