Championship pro golfer Phil Mickelson was working out hard, preparing to compete in the 2010 U.S. Open at Pebble Beach. Unexpectedly, his joints started aching. It felt like he’d sprained a wrist on one hand and somehow jammed a finger on the other. His right ankle hurt too.

He hadn’t done anything to injure himself, so he chalked up the pain to years of practicing for and playing pro golf. He figured it would pass — and it did.

One morning just two days before the tournament, Mickelson woke up in such agonizing pain he almost couldn’t get out of bed. Now he was worried.

With his family’s support and encouragement, he found a rheumatologist. This type of doctor specializes in diagnosing and treating arthritis and other diseases of the joints, muscles, and bones.

The rheumatologist ran some tests, then tournament day came and Mickelson played. In the end, he took fourth place in the 2010 U.S. Open, just three strokes behind Graeme McDowell.

When the lab tests came back, Mickelson learned he had psoriatic arthritis (PsA).

There are many types of arthritis. Some, like osteoarthritis (OA), are caused by “wear and tear” on the joints over time. Some types of arthritis are autoimmune diseases, such as rheumatoid arthritis (RA). Others, like psoriatic arthritis, may have several different triggers.

Genetics, the environment, viruses, and the body’s immune system are all examples of factors that might cause psoriatic arthritis.

Psoriasis

Psoriasis is a fairly common, chronic skin disease that causes patches of new skin to grow too quickly and thicken, mainly over the joints. The patch of skin is covered with silvery-white scales that may be itchy or painful. Another symptom of psoriasis is pitted or crumbling nails, or nails that have separated from the nail bed.

Psoriasis is genetic, meaning that it can be passed down through generations. It may be mild or severe. Although it can’t be cured, it can be treated.

Psoriatic arthritis

One in 20 Americans who have psoriasis, usually between the ages of 30 and 50, also get PsA. Rarely, it appears without noticeable signs of the skin condition and can be difficult to diagnose.

PsA causes inflammation and pain in joints throughout the body. When the hands or feet are involved, it can make the fingers and toes look like sausages, a condition called dactylitis.

Doctors aren’t sure what causes psoriasis and PsA. However, they suspect the conditions may be related to the immune system and how it interacts with the environment in people with genetic susceptibility.

Psoriatic arthritis like Phil Mickelson’s is treated with a variety of medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) and disease modifying antirheumatic drugs (DMARDs) are often tried first.

Because Mickelson’s psoriatic arthritis was so severe, his rheumatologist immediately put him on one of the relatively new biologic response modifying drugs. It was the tumor necrosis factor (TNF) blocking drug, etanercept (Enbrel).

These drugs usually take some time to work. Some work well in some people but not in others. In Mickelson’s case, Enbrel did the job, bringing his arthritis under control and reducing his pain and disability.

Mickelson has been back on his professional golf game for several years thanks to the early diagnosis and treatment of his psoriatic arthritis. And because he’s a celebrity, he has a large, built-in audience. Mickelson has become a vocal advocate for raising awareness about psoriatic and other types of arthritis.

Phil Mickelson will have psoriasis and psoriatic arthritis for the rest of his life — both diseases are incurable. Like many other forms of arthritis, there are times when PsA flares, and other times when it causes little pain or disability. It can even go into complete remission.

With the help of powerful arthritis medications like methotrexate and biologics like etanercept, a healthy diet, and plenty of exercise, Phil Mickelson should be playing golf — and winning tournaments — for a long time to come.