To be sure, cracking your fingers is no way to make friends in a quiet library. But the habit itself won’t give you arthritis — at least not according to clinical studies, including one way back in and one more recently in specifically focused on addressing this myth. Arthritis develops when the cartilage within the joint breaks down and allows the bones to rub together. Your joints are surrounded by a synovial membrane, which contains synovial fluid that lubricates them and prevents them from grinding together. When you crack your knuckles, you’re pulling your joints apart. This stretch causes an air bubble to form in the fluid, which eventually pops, creating that familiar sound. Cracking your knuckles isn’t necessarily good for you, though. While there’s no proven relationship between the habit and arthritis, persistent cracking can wear down your synovial membrane and make it easier for your joints to crack. It can also lead to hand swelling and weaken your grip.