My 82 Year Old Father Has Parkinson's.. He Was Just

My 82 year old father has Parkinson's.. He was just diagnosed 1 year ago.. My question is, he woke up Sunday morning with his foot swollen and very painful to walk on? He never did anything to injure it. He was fine when he went to bed Saturday night. Could this be affects of the disease? Or does it sound like something else? Thank you!