Non-knee causes of knee pain
Probably the most common non-knee related cause of pain in the knee is osteoarthritis of the hip. This is due to a phenomenon called referred pain. Simply put, this is caused because the same nerves supply sensation from the hip joint and the knee joint and the brain can become “confused” as to from where the signals are arising. Any surgeon who sees a number of patients with knee pain for consideration of a total knee replacement will find a proportion of them have hip OA rather than knee OA and actually need a total hip replacement.
Back pathology can cause knee pain as can problems with the feet. If a person has flat feet, then it is not uncommon for them to suffer from anterior knee pain. The correct treatment is not to operate on the knee, but rather to correct the flat foot with an insole.