Text 1 (Questions 1-5)

For 50 years, Dr. Donald Unger was a walking, talking and breathing scientific experiment. Although this scenario may sound like something out of a sci-fi movie, Unger’s undertaking was quite practical in nature. He simply wanted to prove that cracking his knuckles didn’t cause arthritis.

During his five-decade experiment, Unger cracked the knuckles on his left hand and not on his right. The results, published in the 1998, revealed that despite cracking the knuckles on his left hand at least 36,500 times, Unger did not develop arthritis.

However, they are far from definitive proof that arthritis isn’t a real risk. Cracking one’s knuckles can sometimes lead to hand injuries. A handful of scientists have queried whether the force used to crack a knuckle could potentially lead to cartilage damage, although studies have yet to be done on the subject.

The U.S. Department of Defense have funded a research taking a serious look at the matter. They examined the hand X-rays of patients during a five-year period. Patients with arthritis were placed in one group and the patients without arthritis were put in another. People in both groups 15 were then asked whether they cracked their knuckles. And that’s when researchers received some surprising results. Turns out, the people who didn’t crack their knuckles had a slightly greater rate of arthritis than those who did.

Source: Scientific American