What's behind the rise in arthritis?

Osteoarthritis is a common, painful joint condition that affects about 8 million people in the UK, and many others across the world. It stems from a breakdown of the protective cartilage at the ends of bones causing pain, swelling and movement problems, commonly in the knee. Osteoarthritis cases have been on the rise, but not for the reasons you might think. Katie Haylor spoke to palaeoanthropologist Ian Wallace from Harvard University, who has taken a historical perspective on finding out why...