Tennis Ball

One day while jogging, a middle-aged man noticed a tennis ball lying by the side of the walk. Being fairly new and in good condition, he picked the ball up, put it in his pocket and proceeded on his way.
Waiting at the cross street for the light to change, he noticed a beautiful blond standing next to him smiling.
“What do you have in your pocket?” she asked.
“Tennis ball,” the man said smiling back.
“Wow,” said the blonde looking upset. “That must hurt. I once had tennis elbow and the pain was unbearable!”