The perfect total knee is known as “the forgotten knee”.  Patients with a forgotten artificial knee state that the artificial knee always feel normal in daily activities.  This occurs approximately 66 % of the time, according to French surgeons.

Gender, age, body mass index, and preoperative pain were not predictive of outcome.

Inability to fully straighten the replaced knee, preoperative anterior or popliteal knee pain, patellar maltracking, and the diagnosis of psychological depression are associated with an abnormally feeling total knee replacement.

Better or improved knee flexion (bend) is predictive of a naturally feeling knee.

Both the patient and the surgeon have some influence on surgical outcome.  The ability to straighten the knee is often dependent on strict adherence to a post operative rehabilitation protocol (patient controlled factor).  Better pre-operative knee flexion is associated with more post operative knee bend (surgeon selection of patient for surgical treatment).