Joint replacement surgery is the last step in treatment for severe arthritis and is most commonly performed in the hip and knee. When a joint replacement surgery is performed, it is crucial that the components of the implanted prosthesis are properly positioned. Computer- Assisted Surgery (CAS) helps the surgeon in accurately positioning these components. Similar to an autopilot which assists the pilots or a GPRS that aids the sailors to reach their destination easily and safely, CAS helps the surgeon to achieve the desired accuracy during TKR.