Worst exercises for your joints

As we age, our bodies' joints (knees, elbows, shoulders, wrists, and so on) are among the first (of many, alas) parts to wear out.
After years of step aerobics, my knees began to hurt so much that I went to an orthopedic specialist and asked her if she could fix my knees so I could do step classes again. She said, we can work on fixing your knees but you're going to have to give up step aerobics.
Lesson learned! I rarely use a step for exercise, and even then use one or sometimes no riser.
Step isn't the only exercise to avoid if you want to preserve your joints. Check out this article for the "8 Worst Exercises for Your Joints. Here's the top five (or should I say, bottom five):

Jumping jacks -- not a good idea!

• 1.       Jumping jacks
• 2.       Running
• 3.       Tennis
• 4.       Boxing
• 5.       Step aerobics