Tennis is a close second to golf in terms of the potential harm it can do to your body. When you play, most of your weight will be on the same foot, whether forehand or backhand. The thousands of serves and forehands you hit will take its toll on your pelvic and shoulder positions. These will, in turn, affect the elbow and wrists, spine and knees, feet and ankles. At the Professional level, injuries are a revolving door for the players, even though they are young and have “the best” people working on them.