Knee Replacement Implants During knee replacement surgery or hip replacement surgery, an orthopaedic surgeon will resurface your damaged knee or hip with artificial components, called implants. There are many different types of implants. The brand and design used by your doctor or hospital depends on many factors, including: 1. Your needs, based on your knee problem and knee anatomy, as well as your age, weight, activity level, and general health 2. Your doctor's experience and familiarity with the device 3. The cost and performance record of the implant.