One of the first things all amateur golfers learn is they need to keep their front arm (left arm for right hand golfers) straight no matter what. If you go to any driving range in the United States you will find beginner golfers trying diligently to keep that arm straight. If everyone says you have to keep your arm straight you should never bend your elbow, right? Not so fast my friend.
The photo below is one of the best I have ever seen of Tiger. Notice how straight arm is; he has no bend in his elbow at all.
Remember that Tiger Woods is the best player to ever pick up a golf club. When he was three years old he had already learned to swing the club correctly. In fact, he could probably pick a club up in his sleep and put a swing on the ball without bending his elbow. This does not mean this is the only way to hit the golf ball.
The best way to consistently hit the golf ball is to put the same swing on it every time. To do this, keeping an elbow straight is very effective. Unfortunately, most mere mortals and amateur golfers do not have the flexibility to get a full shoulder turn and keep their elbow from bending. If you do not have shoulder, back and upper body flexibility you DO NOT have to keep your elbow straight to be a good golfer. Below is a photo of Rocco Mediate:
Remember that Rocco Mediate almost beat Tiger Woods to win the 2008 US Open at Torrey Pines. Although Tiger was playing on a torn ACL and a broken leg, the performance Rocco put on was still amazing. Rocco has had many back problems which is why he has adjusted his swing to look like this. If you have concerns about back, shoulder or elbow problems in the future it might be a wise decision to slightly bend your elbow at the top of the swing.
When I swing the golf club I do not keep my elbow straight at all times. If I tried to do this I would get extremely sore and I would not score well. Bending my elbow actually allows me to get deeper into my swing which increases my club speed and ball speed coming off the club face. If you want to be a great wedge player you don’t even have to get a shoulder turn at all. I go about half way back with my wedge shots and it allows me to spin the ball quite well. Here is my wedge swing: