My Son's Injured Knee

My youngest son twisted his left knee while he was playing table tennis yesterday. At first he didn't feel any psain but in the evening his left knee started hurting badly. He couldn't stand up on his leg because of the pain. It was Sunday so my wife called the hospital if a doctor could see my son. The nurse said the doctor can see him but the injury is not serious, although they will still charge additional fee, 5,000 yen.

We rushed to the hospital and carried him to the consultation room in a wheelchair. He couldn't move his left knee without pain. My son climbed up to the examination table. The doctor said bend and stretch the knee slowly. My son tried to do that carefully and he did it with no pain! The sharp pain had disappeared. Gone!

I paid the treatment fee, of course, including the additional 5,000 yen. Where did the pain go?