Osteoarthritis — which decade does primary OA typically begin?

• A. 5th to 6th decade of life
• B. 3rd to 4th decade
• C. 7th to 8th decade
• D. 9th decade

Answer: (A)

Primary osteoarthritis tends to emerge as part of aging and wear on joints, so its typical onset is in middle life. The most common timing is the fifth to sixth decades, roughly ages 40s to 50s, when cartilage wear and joint changes start to produce symptoms like pain and stiffness. While OA can occur later, starting in the 60s or 70s is common as well, that’s later than the usual initial onset. Beginning in the 30s–40s is possible in some cases but is less typical for primary OA, which is why the fifth to sixth decade is the best fit.