What Causes Pain In The Right Hip And Knee?

My husband has pain in his right hip and knee. On the left side he has swelling below the knee. His Dr. has had him do ultra sounds for the heart including neck veins, kidney, bladder, liver to rule out major problems. He s done urinary tests, blood tests- all of these have come back normal and good. They believe the hip and knee pain in the right leg to be sciatic, but the swelling below the left knee is still worrying him. He is scheduled to have a CAT scan on Friday for abdominal and pelvis. At this point I m wondering if it could be a DVT. Any ideas or tests that should be used? He is currently on high blood pressure pills, two water pills and a pill for prostate-which has been ruled out through scopes and routine check ups. Last scope was less than a year, last check up for prostate was 2 weeks ago.