Hi. Thanks for your question. From what I understand from your message is that your mother is suffering from a knee problem, typically getting up from a sitting position precipitates pain in her knees. This is called as "theatre sign" and indicative of patellofemoral arthritis. The decision of whether to do a knee replacement is not just based on Xray. It is important to know how far she can walk, if she has any pain at rest and how the pain is affecting her quality of life. Again, if all of these are affected with a bad arthritic knee on an Xray, a knee replacement option is a life changing surgery for many patients.