Can ra, adenomyosis (causes clotting) or a ruptured baker's cyst cause elevated d-dimer. 2 us and neither found clot. lump behind right knee, edema in calf and foot. can't fully extend. no warmth or discoloration. feels like water running down leg?

This scenario certainly suggests that a ruptured Baker's cyst is quite likely. I believe that Inflammatory processes like RA or clotting from adenomyosis can cause elevation of d dimer. In my opinion an MRI would most likely demonstrate the responsible issue with your leg. Discuss this with your MD or attending physician who could speak to the radiologist.

Yes, a ruptured Baker’s cyst can cause above symptoms and is common in RA. D-dimer is a non specific test that will not help at this point in further sorting out the diagnosis. The sensation of water running down the leg suggests a local neuropathy due to compression.