<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, I have been having knee pain for a while now and I have also noticed an absence of menstruation for the past month.  <response>: Based on your symptoms, you might be suffering from systemic lupus erythematosis SLE. It is an autoimmune disease that affects various parts of the body, including joints and hormones. I suggest we run some tests to confirm the diagnosis. 