Patients with knee arthritis will often feel pain, stiffness, instability in the knee, as well as a change in their body alignment. When arthritis of the knee reaches advanced stages, there is typically eroded cartilage and weakening of the joint with patients experiencing increasing pain and dysfunction. Knee replacement surgery, also known as knee arthroplasty, is a procedure where part or all of a damaged knee joint is replaced with an implant in order to eliminate pain and restore function.