Donald was level par for the day when he was forced to withdraw
Britain's Luke Donald withdrew from the US Open after 14 holes of the final round on Sunday because of an injured left wrist.
Donald had his wrist taped up by medical staff but was unable to continue and picked up from the 15th fairway at Torrey Pines.
The 30-year-old Englishman was level par for the day and six over par for the championship.
"He had a problem with it all week," said his brother and caddie Christian.
"It had been feeling sore right from the start and when he teed off on the 15th tee he just felt something go, something pop.
"He immediately alerted tournament officials and told them that he didn't think he could go on.
"He is not sure exactly what the problem is, whether it be one of the muscles in his wrist or whatever but he has gone to see the medic here just to get it strapped up and will go to the doctor next week to see what the problem is."
Donald's fellow Englishman Ian Poulter withdrew after 15 holes of the second round on Friday because of a wrist injury.
He was 14 over for the tournament and playing alongside Donald and Paul Casey at the time.