over the past 34 years my left knew has been operated on 4 times (trim meniscus , clean up and stitch lateral meniscus back in joint( ACL 90% torn), replace ACL, clean up knee again). right leg has had to pick up the slack for the 34 yrs. past 2 years both have been injected with hyaluronic acid. i had xrays a few days ago and was asked by the dr Ever think of having your knees replaced? . would this be a normal question? i have burning pain in both knees when sitting at my desk, can only stand at files for 10-15 min at a time, going up and down stairs i get sharp pains and hang on to both railings.