At what age do you start having arthritis?

Mine started in my knees in my early 30s.

Every person is different.  There is no one set age in which someone will start having issues with arthritis.

Also, arthritis affects different areas of the body for different people.  For example, many people feel arthritis in their hands and fingers first while other people start having arthritis pain in their knees first.  

Typically, arthritis could start before 40, but for the majority of people, it will be sometime after the age of 40 before they begin noticing issues related to arthritis.

Personally, I am 55.  I have no issues in my hands but I do have some problems with my knees.  I do stretches to help maintain range of motion and reduce pain.  (yes - exercise can actually reduce the pain issues when done correctly - I went through some physical therapy to learn the best exercises for my particular issues)

Part of my problems are because I have spent the majority of my working life doing jobs that involve standing for most of the shift - and I work 40 to 60 hours per week.  

Usually around 40. Then by 60 the pain is almost unbearable. By 74, you're in horrible pain 24/7.