When you “crack” your joint, the popping noise is not due to bone rubbing against bone. Instead, when you crack your joints, the joint space expands and causes the joint fluid to form a gas bubble which subsequently pops causing “cracking” sound. The gas then requires a few moments to redissolve into the fluid before the joint can be cracked again.
There exists no evidence that cracking joints can cause arthritis. Arthritis is either a systemic autoimmune disease (rheumatoid arthritis) or a degenerative joint disease due to joint space narrowing (osteoarthritis). However, cracking of the joints can cause laxity and dislocation of the ligaments and tendon surrounding the joint.