Hi Alex.. I have always had pain in my legs because of lower back pain caused by a break in my LV3. After the transplant my legs do hurt but it is because of constant movement including driving as I have two small kids and I have to go about my work. The pain is not severe and I do not need any medication for it. It goes away with rest.
Maybe your legs are very weak right now. You should try and rest more maybe.
Regards