His father, Felipe, turns 78 on May 12 and needs right knee replacement surgery later this spring.

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He was with his mother, Eunice Simpson, who was undergoing knee replacement surgery at Saint John's Hospital in Santa Monica.

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Having to undergo surgery was not good news for Gray, though total knee replacement surgery is among the most common surgeries performed today in the United States.

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After knee replacement surgery a few years ago, Traum stopped running himself and switched to a hand-crank wheelchair, which is low, has three wheels and is moved by the user's arms.

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Meanwhile, Mr Tuttle, who had knee-replacement surgery in July, is running his campaign from his kitchen table or his front porch.

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Xarelto is already FDA-approved to reduce the risk of DVTs and PEs from occurring after knee or hip replacement surgery (July 2011), and to reduce the risk of stroke in people who have a type of abnormal heart rhythm called non-valvular atrial fibrillation (November 2011).

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He suffers from a degenerative bone disorder in his hip and has had surgery for prostate cancer, a quadruple heart bypass and a double knee replacement.

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