Xrays can be used to determine the severity and progression of disease of a hip or knee replacement but they are never used to make the decision about WHEN to perform the surgery. In the video above, I go over some of the aspects we look for on Xrays.
How recent should an Xray be to be useful
If this is the first tie you are seeing me (or your orthopaedic surgeon), then it is best to have an Xray that was at least performed within the last 12 months. This enables a more recent review of your joint. A hip and knee Xray should be performed when you have symptoms only, and certainly should not be done routinely if you are not considering a joint replacement operation, or intervention.
Should I get an MRI?
In general, an MRI is not necessary in making the diagnosis of osteoarthritis of the hip and knee. Occasionally, when there can be competing pathologies or what the Xray do not reflect the same as the symptoms you are experiencing, then an MRI should be performed to clarify the situation.