Is lumbago a treatable condition?

Very much so: "lumbago" is simply a fancy medical term for low back pain. In many cases, low back pain is very treatable and often responds well to osteopathic manipulation. In the hands of a skilled physician, omm has been shown to be very effective at treating low back pain while reducing the need for drugs and surgery. I would suggest hunting down a local do and see what they can do for you.

Yes: There are mutiple treatments starting with lifestyle changes: no smoking, weight control & regular exercise. If no contraindications, medication can help as well as a back support. Modification of activities that affect the back is also helpful. Sometimes pain management injections & physical therapy can help.