One important thing to understand about the golf swing and injuries is that the weakest joint in the chain will usually be the first sign of problems. If a player fights balance issues to make solid impact, it will usually show up in the ankle joint in one way or another, then the knee and then the hip. This isn't always the case, but often the weakest joint can alert you to problems.
If a swing is out of sequence, if the release is poor or if there is a sudden deceleration, often the wrist will show wear and tear first, then the elbow and then the shoulder. Sometimes, the problem goes smaller than the wrist to the thumb joint. It is important to understand this vulnerability so you can be aware of learning to protect the smaller joints through proper sequence, providing tension in the proper places and strengthening all of the joints as protection.
Here is an example of a player with a thumb joint problem. With all due respect to Peter Kostis, who lauds Kim's "triangle" through his finish position, I believe it is the thing that forced him out of the top tier in competitive golf. With a locked left elbow, the force of the deceleration that every part of the body makes before impact was absorbed by his wrist and thumb and possibly a bit by his shoulder or back also.
Here is a shot of a position that I wouldn't want to see in any of my players. This was from :44 of the above video. It seems like a great thing to keep your left arm straight, but understand that deceleration of the club means your body harnesses a lot of stress and strain.
The joints of the left side can work together to harness the deceleration of the golf club after impact and do it with control. Here is Rickie's swing and it shows this idea clearly.
This is Rickie Fowler at last week's Scottish Open. Shortly after impact, Rickie's left arm rotates and folds, allowing his bigger muscles to absorb the brunt of the deceleration of the golf club. It also allows him to be in better control of the handle of the club, because of the softening of the stronger joints. Their softening through rotation and bend allows the hands and wrists to stay firm and in control.
Anthony Kim is a great player of the game, but his story is a common one these days. Players work so hard to reach the top of the ladder only to feel let down by injuries. By understanding the importance of placing tension in the right places as you swing, you can prolong your career by protecting your joints. If you want control in the weakest joints, you must allow stronger joints to absorb the stress through bend, fold or rotation. One of the messages of this blog is to simply do what your body allows you to do as a young player. If you are unable to make a move after a lot of work, it might be that your body simply wasn't put together to do it that way. There are many ways to swing a club and copying another swing might lead to problems. Swing the way that your body allows. Also, understand that anything done well can be overdone. If Jordan Spieth had listened when people said the left arm needs to be straight at the top of the swing, would he be enjoying his success right now?
If you would like to read more about acceleration, deceleration, joint protection, etc. then check out these links:
My favorite article from TPI.
Paige M's story of injury