(MONEY Magazine) – Spring is here, and as a winter-weary nation resumes outdoor activities like golfing and gardening, a resounding cry can be heard throughout the land: Oh, my aching back!

Back pain is nearly as common as the cold: Some 80% of Americans suffer from it at some point, racking up medical bills and lost productivity estimated at $50 billion a year, according to the federal Agency for Health Care Policy and Research (AHCPR).

One in three Americans with back pain turns to a chiropractor for relief, according to a study published in the journal Spine. Though they're often thought of as "back doctors," chiropractors, who treat patients by manipulating the spine with their hands or small tools, are not medical doctors. They don't attend med school and can't prescribe drugs. Theirs is a quasi-medical tradition whose origin lies in a centuries-old type of folk medicine called bonesetting.

Should you see a chiropractor for a "spinal adjustment" the next time you wrench your back? Like several other folk practices, chiropractic has some demonstrated value: Studies published during the past 15 years show that chiropractic can help relieve acute lower back pain or shorten its duration, especially if treatment is started within the first month. (Chronic back pain, which is discussed below, is a different story.) The AHCPR endorsed chiropractic in lower back treatment guidelines issued in 1994, and Medicare has covered it since the 1970s. Some 80% of workers have some chiropractic coverage in their health plans. But some studies also show that other methods--including physical therapy and the conventional medical treatment of rest and pain medication plus mild exercise--can be just as effective at the same or lower cost.

A study published last October in the New England Journal of Medicine, for example, followed 321 Seattle-area adult HMO members whose lower back pain had lasted more than seven days. Patients were provided with either a month of chiropractic manipulation, a month of physical therapy or one or two visits to the family doctor and an educational booklet on back pain. At four weeks, the physical therapy and chiropractic groups reported slightly less severe symptoms. Over a two-year period, however, the study found no significant differences among the three groups in the number of days of reduced activity or missed work or in the recurrence of back pain.

The significant difference was in the amount of money spent by the HMO during the two years of the study. While physical therapy and chiropractic treatment in the Seattle study cost about the same--$437 and $429--the booklet and doctor visits cost only $153. Patients spent the same amount--$5 to $10--for a visit to any of the practitioners, but they saw chiropractors, on average, more than three times as often as they saw the doctor. And the patients--in this study and in numerous others--tended to be more satisfied with chiropractors and physical therapists. In the Seattle study, for example, 75% of patients in the physical therapy and chiropractic groups rated their care as very good or excellent, compared with only 30% of the medical group.

There's no conclusive clinical evidence that chiropractic helps chronic back pain (that is, pain lasting longer than three months); but chronic back trouble is difficult to treat by any means, says Dr. Paul Shekelle, who has studied chiropractic care and costs. Surgery is helpful in only one in 100 cases of lower back problems, says the AHCPR; it is best reserved for specific conditions like herniated disks, fractures and spinal stenosis, a narrowing of the spinal canal.

Choosing a chiropractor

If you decide to go to a chiropractor, your first step should be to find one who will work closely with your doctor. That sounds easier than it may be, because the medical establishment has been at odds with chiropractors for most of their controversial history. In fact, the American Medical Association barred members from referring patients to chiropractors until a federal court ordered it to end the boycott in 1987.

When interviewing a prospective chiropractor, find out whether he or she considers the practice a complement to conventional medicine or a substitute. Roughly 80% of chiropractors believe that spinal misalignment is a significant cause of disease. If yours endorses chiropractic's use for nonmusculoskeletal problems, such as asthma (for which studies show it is not useful), or encourages you to think of him or her as a primary-care provider, you may want to choose someone else. "I would have the most confidence in a chiropractor who does mostly spinal manipulation and not megavitamin therapy and ultrasound and all that sort of thing," says Dr. Richard Deyo, author of several studies of chiropractic care.

Both the AMA and consumer groups recommend seeking out practitioners who describe themselves as "scientifically oriented chiropractors." These professionals confine themselves to the treatment of musculoskeletal conditions by manual methods alone. If you have trouble finding one, call the 3,000-member National Association of Chiropractic Medicine in Houston (281-280-8262) or go to its Website (www.chiromed.org) for information.

The most traditional chiropractors, who use spinal manipulation almost exclusively to treat a variety of ailments, belong to the International Chiropractors Association of Arlington, Va. (www.chiropractic.org). But most chiropractors mix their discipline with other alternative healing practices. These practitioners belong to the American Chiropractic Association (www.amerchiro.org) in Washington, D.C.

What to expect

If done properly, back or neck manipulation should not be painful, although you will hear characteristic cracks and pops as vertebrae are pushed and pulled. The majority of experts advise against forceful neck manipulation because of the slight risk of injury and accident (estimates range from one in 200,000 to one in a million). You may feel some relief immediately but should expect to make up to nine visits over a two- to three-week period. You should not feel increased pain after a visit. If you do, call your physician.

Don't be pressured into springing for an extensive series of X-rays or other ancillary services or products, such as homeopathic remedies. "Chiropractors shouldn't be prescribing herbs because they are not trained in pharmacology," says Samuel Homola, a retired chiropractor and author of Inside Chiropractic: A Patient's Guide. If you don't get relief from chiropractic in four to six weeks, go to your primary-care provider for further evaluation.

Medical experts--with the exception of most chiropractors--don't believe that routine spinal adjustments prevent future bouts of back pain. Staying fit and maintaining correct posture do that, so you shouldn't need a standing appointment with your chiropractor.