Its easy to overlook your thumb. It looks simple, but its responsible for so much, from holding a golf club to pinching your grandchilds cheeks. If you engage in activities that involve repetitive pinching or grasping motions, your thumb is more likely to wear and develop arthritis, particularly at the base. With arthritis, suddenly your thumb cant be ignored. "If you dont have a functioning thumb, you lose 50 percent of the function of your hand," says Cleveland Clinic orthopaedic surgeon William Seitz, MD. "Your thumb also represents 50 percent of the function of your hand when youre grasping or manipulating, so its at risk for injury in a lot of different activities."