Key insights

• 💥 Popping joints can be caused by rapidly stretching ligaments
• 🔘 Presence of bubbles within the joint leads to the popping sound
• 🍳 Synovial fluid in joints contains long lubricating molecules like hyaluronic acid and lubricin
• 🌀 Synovial fluid in joints creates a low-pressure zone that pulls out dissolved gases, forming a bubble
• 💢 Popping your joints may temporarily enlarge them, but it doesn't cause arthritis
• 🏅 Dr. Donald Unger cracked his knuckles for 60 years, won Ig Nobel Prize for debunking arthritis myth
• 🖐️ Knuckle-cracking may weaken grip and annoy others
• 😤 The biggest proven danger of knuckle-cracking seems to be annoying others around you

Q&A

• What are the potential effects of knuckle-cracking?

  Dr. Unger's experiment also suggested that knuckle-cracking may weaken grip and cause hand swelling. However, the biggest proven danger of knuckle-cracking seems to be annoying others around you.

• Does popping joints cause arthritis?

  Popping your joints may temporarily enlarge them, but it doesn't cause arthritis. Dr. Donald Unger cracked his knuckles for 60 years and remained arthritis-free, disproving the myth that cracking joints causes arthritis. He was awarded an Ig Nobel Prize for his experiment.

• What is the function of synovial fluid in joints?

  Synovial fluid in joints cushions and cleans, contains phagocytic cells to clean up debris in the joint, and contains lots of dissolved gas molecules. It also creates a low-pressure zone that pulls out dissolved gases, forming a bubble that later collapses, and the gases dissolve back into the fluid over about twenty minutes.

• Which parts of the body can be cracked?

  Various joints in the body, including fingers, neck, back, hips, wrists, and shoulders, can be cracked. These joints are synovial joints and contain synovial fluid, which has a texture similar to egg yolk.

• What causes the sound of popping joints?

  The sound of popping joints is caused by rapidly stretching ligaments and the presence of bubbles within the joint. When the joint is stretched, the pressure inside the synovial fluid drops, causing the gas to form a bubble, which then collapses and the gases slowly dissolve back into the fluid over about twenty minutes.

• 00:09 The sound of popping joints can be explained by rapidly stretching ligaments and the presence of bubbles within the joint. Scientists have offered various explanations for this phenomenon.
• 00:45 Synovial joints in various parts of the body can be cracked due to the presence of synovial fluid, which has a texture similar to egg yolk.
• 01:18 Synovial fluid in joints cushions and cleans, contains dissolved gas for cracking knuckles by creating space between bones.
• 01:56 The synovial fluid in joints creates a low-pressure zone that pulls out dissolved gases, forming a bubble that later collapses and the gases dissolve back into the fluid. This process takes about twenty minutes.
• 02:32 Popping your joints may temporarily enlarge them, but it doesn't cause arthritis. Some scientists believe there may be two pops when cracking a joint. Dr. Donald Unger disproved the myth that cracking joints causes arthritis.
• 03:17 Dr. Unger cracked his knuckles for 60 years, won Ig Nobel Prize for debunking arthritis myth, suggested further investigation into parental beliefs, knuckle-cracking may weaken grip and annoy others.