# Proof Narrative: Cracking your knuckles regularly causes arthritis later in life.

## Verdict

**Verdict: DISPROVED (with unverified citations)**

This one's a myth. The scientific record is unusually consistent: knuckle cracking does not cause arthritis.

## What was claimed?

The claim is a familiar warning — that habitually cracking your knuckles will leave you with arthritic hands later in life. Many people grew up hearing this from parents or doctors, and it persists as common health advice. If true, it would be a meaningful reason to break the habit.

## What did we find?

The evidence against this claim is both clear and consistent across decades of research. Two independent peer-reviewed studies, conducted 21 years apart with different patient populations, both examined this question directly and reached the same conclusion: knuckle cracking does not increase the risk of arthritis.

The earlier study, from 1990, followed 300 patients and found no elevated rate of hand arthritis among habitual knuckle crackers compared to non-crackers. A 2011 study took a larger, more controlled approach — 215 participants, comparing those with hand osteoarthritis against healthy controls — and again found no significant difference in arthritis rates between crackers and non-crackers (18.1% vs. 21.5%).

Harvard Health Publishing and the Johns Hopkins Arthritis Center both state directly that there is no evidence knuckle cracking causes arthritis. These are independent institutional assessments, not rewrites of the same study.

Researchers also looked specifically for any published study that might support the other side of this question. After searching the medical literature, none was found. Every study that has examined this question has come to the same conclusion.

## What should you keep in mind?

One of the four sources was only partially verified — the journal page's formatting made exact quote matching difficult, though the study's finding is well-established across multiple sources. The disproof does not depend on that single citation; the remaining three verified sources are independently sufficient.

There is one genuinely interesting nuance buried in the 1990 study: habitual knuckle crackers did show reduced grip strength and occasional hand swelling compared to non-crackers. This finding doesn't reverse the conclusion — the same study explicitly found no arthritis link — but it suggests that heavy knuckle cracking may not be entirely consequence-free in other ways.

The question of *why* knuckle cracking makes that sound (gas bubble formation in the fluid surrounding joints) has also been studied, and no evidence shows that this process damages cartilage. The forces involved are well below what would cause joint injury.

## How was this verified?

This claim was evaluated by collecting independent authoritative sources — peer-reviewed studies and major medical institutions — that directly address whether knuckle cracking causes arthritis, then checking whether the evidence for or against the claim crossed a pre-set threshold. You can read [the structured proof report](proof.md) for a full breakdown of the evidence, or examine [the full verification audit](proof_audit.md) for citation-by-citation verification details. To reproduce the analysis from scratch, you can [re-run the proof yourself](proof.py).