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 started just before the US Open 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 practise 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.'
