His left knee became inflamed and he visited a number of doctors to diagnose the problem, but almost a month later, medics have yet to determine the cause of his ailment, despite running numerous tests. "I was in Africa about three and half weeks ago and I stepped in a ditch in Mozambique. It was a hidden ditch, I was in a village and it was full of muddy water and I stepped in it and hyper extended my knee," the Daily Express quoted him as saying.
"It got stiff and worse and worse. It was painful, I couldn't really move it too much. I came back to New York, went to a doctor here, they did an MRI (scan), discovered some arthritic elements. It got worse, then I went back home to Los Angeles and went to see another doctor, apparently the best knee guy."
"He looked at it and said, ''You got a lot of fluid there, we gotta drain some of the blood out.'' So he stuck a needle in and sucked out the blood. He had this look in his eye and was like, ''This isn't blood''. I said to him, ''What is it?'' and he said, ''I don't know''. So they've been doing cultures (tests) on it, they took two more samples. They think it might have gotten infected, they''re not sure," he explained.
Stiller's mystery injury was so painful it almost forced him to pull out of a scheduled interview with U.S. TV talk show host David Letterman on March 23. But, after more examinations and tests, Stiller''s doctors now believe he may have contracted Lyme disease, an easily treatable inflammatory illness spread through a tick bite, which is common on the East Coast of the U.S.
Stiller admits he's been experiencing "little night sweats" as a result of the condition, but he's glad his medical mystery is almost solved - because it means he won't have to undergo invasive surgery. "It's actually improved so much in the last 24 hours, but I almost couldn't come (to New York), I didn't get the go ahead (from doctors)... He (his doctor) sent me to a rheumatologist, an infectious rare disease guy, so they do all these tests," he tells Letterman.
"I got this call at like two o'clock in the afternoon (on Monday). The guy said, ''Have you ever had Lyme disease?'' I said, ''No, but I was on the East Coast last summer and my son had Lyme disease''. And he said, ''Well, it's looking like it might be Lyme disease. He was saying if it wasn't, I'd have to have an orthoscopic procedure, so if it is Lyme disease, I won''t have to have the procedure done, which is great," he added.