Linda Nielsen remembers vividly the day her knee first swelled up. She was 7 years old and had just received a live-virus immunization for school.

That swollen knee didn't go away. Despite visits to the doctor, the climb up the hill to her house after school was murderously slow and painful.By the time her doctor sent her to a rheumatologist, "it had pretty well spread to all my joints."

"It" has been her companion for 28 years: rheumatoid arthritis.

When most people think of arthritis, they picture osteoarthritis, the type that usually comes with age and is caused by degeneration of the joint's cartilage. Rheumatoid arthritis is more capricious. It can strike as young as 18 months, though it most commonly affects women between 30 and 45. More than 70,000 American children live with the disease.

It is also a vicious illness, marked by pain, tenderness and swollen joints. In some cases, it destroys cartilage and causes joint deformities. It can also lead to premature death, according to the Arthritis Foundation.

Unlike osteoarthritis, rheumatoid arthritis is an autoimmune disease. The body's im-mune system attacks and damages the joints and sometimes other organs. It can completely disable someone. People with the illness may also develop nodules under their skin, close to the joints. Others might become anemic or experience dry eyes and mouth.

Dr. Patrick Knibbe, a rheumatologist in Salt Lake City, describes two forms of the illness: one explosive, where all the joints swell at once. And the more common type, gradually involving more joints and increasing in severity. Some people have periodic episodes; for others, it's more or less continuous.

From the time she was a child until her mid-20s, Nielsen's life revolved to some degree around the whimsies of the arthritis. Pain dogged her steps during the school years. "I never knew what would set off a flare up," she said. "It limited my capacity to be responsible for myself. I wouldn't know what I could plan on for the day until I woke up. And even then it could change several times a day."

Facing hip replacement at age 25, she didn't want to survive the operation. Instead of death, however, she tasted freedom. "My life completely changed. I had a functioning joint."

Medicine and technology have progressed to her benefit, Nielsen said. Medications allow her to control her pain and minimize further ravaging of her joints. Now she deals mostly with damage control, facing the harm that was done to her body before she received treatment. She describes herself as "in control" of her disease now.

Getting medical attention immediately is essential, Knibbe said. If you wait to see if the pain and swelling will leave, it could be too late.

"The first two years of the disease are when most of the damage is done," he said. With early treatment, there's a better prognosis. After that, it's an "irreversible process." And the damage can be considerable.

There's no cure - yet, he said. But there are "multiple treatments, some old, some new." Doctors use a combination of three drugs in the early stages. Some prescribe injectable gold. Other treatments include cortisone, injected or by mouth. Anti-inflammatories are used to help with pain, although Knibbe said he prefers the disease-modifying medications because some of the anti-inflammatory drugs have serious side effects. Doctors can also use a combination of all those options. A balance of exercise and rest is also important for relief.

In many cases, progression can be slowed or halted, pain relief provided and some erosions may even heal.

Early symptoms of rheumatoid arthritis include stiffness - particularly in the morning that doesn't subside a half-hour or so later. Obvious swelling is a clue. So is a "post-midday slump with fatigue that people get. When they rest from that," Knibbe said, "they feel stiff again."

While Nielsen has been impressed that her options have improved, medically, Knibbe said progress is just getting started. "This is going to be a big year for people who suffer from rheumatoid arthritis."

A couple of new drugs should be out within six months that have been "noised about in the press and really awaited. They look relatively promising," Knibbe said.

He's talking about Enbrel, the first drug produced by the biotechnology industry - in this case, Immunex Corp. - aimed at rheumatoid arthritis and other promising drugs that are right behind it, including Arava by Hoechst Marion Rous-sel Inc.

Centocor Inc. hopes to get approval for a similar drug called Avakine in a year or two. Since an FDA panel recommended approving Avakine to treat bowel inflammation, doctors may be able to prescribe it sooner than that.

Other medications, by Searle and Merck & Co., are being hailed as "super aspirins" for their anti-inflammatory properties without side effects like internal bleeding and ulcers. That class of drug, called Cox-2 inhibitors, only relieve symptoms. Enbrel, Arava and Ava-kine may slow progression of rheumatoid arthritis. But they won't heal previous damage. And all the therapies will be needed for a lifetime.

That's why the secret lies in getting medical attention early, Nielsen said. If the amount of damage done to the joints is limited, people can lead nearly normal lives.

Nielsen said she had to learn to take control of her disease herself. She did that in a self-help class, sponsored by the Arthritis Foundation. She listened to her doctor, and together they determined a medical protocol that works for her.

Mostly, though, she wouldn't bow to the disease. She was always on the honor roll in school and got scholarships to college. She served an LDS mission, which others said she wouldn't be able to do. She got married and had a child, who is 9 months old.

She has it all, she said. And if some things have "been difficult to do, there are workable ways in almost any situation."