The joints that "crack" most often are the joints in the knuckles, knees, ankles, back, and neck. For some, joint cracking is a sign of nervousness, for others, cracking the joints bring relief.
Research shows that cracking the joints does not cause arthritis, nor increase the risk of coming down with arthritis.
Arthritis is the inflammation and stiffness of one or more joints in the body, while the cracking sound made by the joints happen when air bubbles pop or burst in the joint fluid (Synovial fluid). Synovial fluid helps to lubricate the joints.
Donald Unger, a medical doctor from California, took up a challenge to prove his mother wrong after she told him that cracking the fingers could cause arthritis. For 60 years, he cracked the knuckles on his left hand at least twice a day and did not crack the knuckles on his right hand.
After 60 years of one-handed knuckle cracking, he did not developed arthritis so he proved his mother was wrong. He published his findings in the journal "Arthritis and Rheumatism" in 1998 and later received an Ig Nobel Award in Medicine in 2009.