Read: Q&A: Rheumatoid Arthritis

Even though "crepitus" comes from the Latin word for "creak" and has the same root as "decrepitude," its snap, crackle and pop sounds do not necessarily signify advanced age. The sound arises from air or other gases in tissue under the skin. For example, crack your knuckles and the microscopic nitrogen bubbles inside pop to attention. But since it takes a while for the gas to build back up, you have to be patient before doing it again for your own delight—or the annoyance of those around you. And while crepitus can be a sign of arthritis, no evidence exists that popping your joints causes the condition. Crepitus may indicate cartilage wear or an injured joint, and the grimace-inducing noise also may be heard when fractured bone fragments move against one another. 

Read: Ask a Doc: Is Knuckle Cracking Bad?