Your surgeon will need to make an assessment of whether it is reasonably safe for you to undergo the knee replacement operation. The assessment is based primarily upon your physical fitness, your medical history, physical examination and the results of any tests. Age on its own, no matter what, does not preclude surgery. The Queen Mother did very well from her hip replacement operation done in her nineties! If there are any major medical issues then your surgeon may well arrange an appointment for you to see his anaesthetist (the doctor who will be putting you to sleep for the operation). The anaesthetist will have more experience in the management of medical problems after the operation and he or she is also in a position of making a better judgement on the implications of those conditions on the anaesthetic he will be using. In more complicated cases he may ask for further testing to be carried out prior to the operation.