Dominic Thiem says the knee injury that has kept him out of the clay season so far was also bothering him at the Australian Open earlier this year.
The world number four is yet to play a match on his favoured clay surface this year after pulling out of both Monte-Carlo and Belgrade.
He revealed last week that the reason for his withdrawals was not the persistent foot injury he has known to struggle with, but a knee complaint instead - and it's apparently been a problem he has always managed.
"It is a congenital problem that sometimes appears in my knees," Dominic Thiem told Der Standard.
"People know it now but it takes a few weeks to disappear. It already hurt in Australia, and although it hurts a lot, it will disappear."
Thiem has also been fighting to regain his mental spark after admitting he 'fell into a hole' in terms of his hunger after winning the US Open last year.
It is something he has always been very open about, and he says he is still working through the process of refocusing his goals.
"When you fight for a goal, you leave everything for it and you achieve it, everything changes," he explained.
"However, in tennis everything goes very fast, you don't have time to enjoy the victory, and if you are not 100%, you lose. It happened to me this year.
"The best thing is not to go to the tournaments if you are not well," he explained.
"If I had played in Belgrade and had lost in the first round, I would have entered that negative spiral. I prefer to be at home."
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