©Wellcome Library, London

In this operation, the articulating joint surfaces of the thigh bone (femur) and shin bone (tibia) are removed and replaced with a metal and polyethylene prosthesis. The red, mauve and green objects on the surgeon's instrument tray are colour-coded ‘trial' joints which are used to determine the size of prosthesis required.

Pencil and crayon drawing by Virginia Powell, London 1997.