The government is into pain.

Oh, not belt buckles, leather and heavy metal, not that kind of pain.

Rather, the kind that comes when a man slips on the job and bangs up his spine, producing shooting pains down into the legs that make work impossible.

In a few weeks his medical condition stabilizes. Physical deterioration is arrested. The pain should be receding. But the patient says it is as bad as ever. Eventually he files for Social Security disability insurance payments, which go to workers found to be so severely disabled that they are incapable of performing any job.

That's when the government gets involved.

Under the Social Security Act, a worker who is under 65 can receive monthly disability payments, with extra allowances for wives and children, plus Medicare benefits, as long as the inability to do any work lasts. About 2.7 million such workers and 1.2 million dependents are on the Social Security disability rolls for a variety of physical and mental impairments.

But "pain is subjective," says Dr. Marc Hertzman, a professor of psychiatry at George Washington University medical school, who is a member of a special government commission on pain. "It cannot be measured," says Dr. Eric Cassell, professor at Cornell University medical college, also a member.

So before granting benefits, the government wants to be sure the patient isn't lying -- either making up the pain or exaggerating it. It also wants to be sure that even if not lying, he isn't unconsciously enlarging the pain.

And that's where the patient and the Social Security Administration clash.

Over the years Social Security has turned down tens of thousands of applicants whose claimed incapacity to work was based in whole or in part on pain. Because there was no provision in the disability law that spelled out how to deal with pain, the Social Security Administration adopted its own internal guidelines: their rule has been that because of the difficulties of measuring pain, subjective evidence of pain by itself cannot be the basis for a disability award.

Instead, an applicant for benefits must show evidence of an underlying physical or psychological impairment. If the impairment by itself is not severe enough to prevent the person from working, SSA will then look at claims of accompanying pain, and may conclude that the combined impact of the impairment and the pain is sufficient to prevent work. But it will not accept the claim if it believes that the accompanying pain is out of proportion to the impairment in question.

These rules have been strongly challenged. Critics say thousands of people unable to work because of genuine pain are being refused benefits and pauperized by the underlying-impairment requirement.

Cassell, an internist, says pain can be real even if not traceable to a medical cause -- simply because science may not yet have discovered the disease or condition causing it.

Courts have frequently accepted subjective evidence of pain and have ordered benefits in cases where Social Security had found claims of pain not adequately linked to a diagnosable medical cause, or out of proportion.

In 1984, during action on a bill changing various other disability provisions, Sen. Daniel Patrick Moynihan (D-N.Y.) insisted that "there is such a thing as disabling pain, which, while the causes cannot be confidently diagnosed, can be shown to exist by accompanying changes in patterns of activity." He argued for an amendment to allow benefits for such pain.

But Sen. Russell B. Long (D-La.) and others said paying for pain that is not clearly the result of a diagnosable medical cause would invite a vast enlargement of the rolls.

Moynihan's proposal was not adopted. Instead, Congress ordered a study of pain by a special commission. Pending completion, it made the Social Security rules mandatory by writing them into law for two years.

Some of the issues in the commission study: Can pain be measured in any objective way? Would it be feasible to authorize disability benefits based on pain alone, without requiring demonstrable medical impairment? Is there any kind of treatment that can return to the labor force people who claim chronic pain but are otherwise physically and mentally capable of working?

These questions are not negligible. They involve billions of dollars a year and affect countless lives. Every year Social Security gets 100,000 applications for disability benefits in which pain is a factor, either alone or [in the vast majority of cases] in combination with some identifiable medical condition. Two-thirds involve back pain. Similar issues arise in veterans' benefits, workers' compensation and private disability insurance.

According to David Koplow, commission member and assistant professor of law at Georgetown University law school, "One of things I've learned on the commission is that doctors feel that deliberate malingering is not a big problem. They can spot that." Koplow said malingerers seem to be a relatively small percentage of the cases. The bigger problem, he said, is pain that is genuine, but not measurable with current medical technology, like migraine headaches.

An even bigger one may be an imperfectly understood condition called "chronic pain syndrome," which is not the same as chronic pain.

In a 1981 article, commission member Dr. David W. Florence, then director of the chronic pain rehabilitation program at the Sister Kenny Institute and assistant professor at the University of Minnesota medical school, said he had found in a series of cases involving low back pains that only 20 percent "are either overtly or covertly fraudulent."

Instead, he found a widespread incidence of chronic pain syndrome, which he defined as a perception of pain and a view of oneself as pain-afflicted, that involves a mix of some actual pain with "hysteria, depression and hypochondriasis."

The pain often starts with an identifiable physical condition, Florence said, but persists long after the condition is arrested. It usually results from a condition of stress and a feeling of incapacity to cope.

According to Florence, the usual patient "is male and between 25 and 50 years of age, has a limited education [often being illiterate], and is married to a woman who is of greater education and intelligence than he and who works in a more skilled capacity . . . ."

"Problems usually arise first within the marital framework, following which a noncritical work-related incident occurs. The patient becomes totally devastated by pain and incapacitation, from which he is incapable of recovering, and does not return to work. Frequently the patient will walk with a cane, usually self-prescribed," Florence said.

GWU's Hertzman said there is agreement that something along that line seems to exist, although it is not clear in many cases whether the syndrome caused the pain or the pain caused the syndrome.

Faced with these uncertainties, the commission, which held its final meetings last week, did not recommend that Congress authorize benefits based on subjective evidence of pain.

Instead, it has decided to recommend that current rules be extended, that studies be undertaken to find a usable form of pain measurement, that experiments with the concept of disability due primarily to pain be undertaken, and that experiments be conducted on how to relieve chronic pain syndrome through physical, psychological and vocational therapies.