World number two Phil Mickelson has revealed that he is suffering from psoriatic arthritis.
It is an inflammatory joint disease which can cause stiffness, pain and lack of movement, but Mickelson said: “Everything is fine now.”
He was on anti-inflammatories during the Scottish Open and the Open last month — he missed the cut at Loch Lomond and was only 48th at St Andrews — but for the last two weeks has been injecting himself weekly with a drug that he has been told to take for the next year.
The problem had started just before the US Open back in June.
“I woke up and had intense pain in some joints and tendons, so much so that I couldn't walk,” he added.
“It progressively got worse, so I got it checked out.”
One of the by-products of the disease is that Mickelson has become a vegetarian.
He is part of a group which owns the rights for a burger chain in California and on that joked: “We're working on a veggie burger!”
Since starting his injections Mickelson said he had been able to “swing and practice full bore.”
He added: “It was a little bit concerning, but I've had some great doctors and things have been looking great and long-term there shouldn't be any issues.
“It's very treatable and the medicine I've been taking has been very helpful. I feel 90%.
“Heading into the PGA I'm probably not as sharp as I would like to be.
“I didn't play well at the British obviously, I didn't play well last weekend (when he missed another chance to take over as world number one from Tiger Woods), but I believe that the game's coming around.”
As well as not being able to walk when the disease struck, Mickelson also had a sprained left index finger and sprained right wrist.
“Then it started getting worse into other joints, the hips and ankle and elbows and shoulders. That's when I got concerned.
“The treatment is a thing called Enbrel. I give myself a shot a week and it lowers my immune system and stops it from attacking the joints.
“I've had some good immediate response and that's why I feel comfortable talking about it, knowing that long-term and short-term things are fine.
“This has put it in remission. It's not that it's cured, but it may never come back, or if it does I'll
start the treatment again and should be able to live a normal life without having any adverse effects.”
Rory McIlroy played with Mickelson for the first two days at Firestone last week and says it was a great experience to watch him at close quarters.
“Playing with Phil those two days was great and I played pretty well the whole week,” he said.
“It was the sort of week where I felt I was playing good but couldn’t really get a lot of momentum going on the course.
“I finished in the top 10 which was good but I felt that if I could have got a few more things going then it could have been a really good week — but that’s the way it goes.
“However, it was a good week for preparation for the US PGA and I feel like I got a lot of good work done on that front.
“So after four rounds in the sixties I’m feeling pretty confident going in to the last major of the year at Whistling Straits.”
McIlroy was confident enough in his long game to concentrate solely on his work from 100 yards out in practice at the start of the week, skipping Monday’s practice round.
“That’s the one area of my game which could have been a bit sharper last week.
“I’m going to get in a full practice round, though, and be ready for the off on Thursday.”
McIlroy, third favourite with the bookies behind Mickelson and Woods to win his first Major, reckons his length from the tee will be a definite advantage this week.
“The Whistling Straits course is long and I feel that my driving is in really good shape,” he said.
“I started hitting it really long last week and if I keep that up it’ll definitely be an advantage round here.”