American love sports……what is the passage mainly talking about?
Americans love sports—they love to play them,to watch them on television,and to talk about them.But this hobby sometimes has serious results—at least to the players.For example,when people play tennis,sometimes they hurt their elbow（肘部）and in this way they develop “tennis elbow”.Also it is easy to hurt a knee in a football game.These injuries（损伤）happen while the player is having fun,but they still hurt.
A few months ago,Kathleen Simmons,who loves playing volleyball,hurt her knee in a volleyball game.Her doctor told her that she needed a very difficult operation（手术）or she might not be able to play again.She felt very sad and didn’t know what to do.
Then Simmons learned about “video operation”.With the help of this new science in medicine,doctors can now repair many injuries and get people back on the playing field and back to their jobs much faster.Simmons found a hospital that was using this new science and went to see the doctor there.The doctors told her the operation could help.
For this operation,her doctor didn’t have to open her knee.Instead he put a very small camera lens（镜头）inside her knee.The lens sent back pictures,which appeared on a television screen.As he worked,he could see the inside of her knee on the TV.With the help of the large pictures on the screen,the doctor knew exactly what to do when he was making the repairs.
what is the passage mainly talking about?