A visibly squarer jawline from an enlarged chewing muscle comes up constantly in both TMJ and appearance-focused discussions — and the relationship between the two runs in both directions.
What masseter hypertrophy actually is
The masseter is the main chewing muscle, running from cheekbone to jaw. When it enlarges — from genetics, habitual clenching, chronic gum chewing, or heavy one-sided chewing — it can visibly square off the lower face, which is part of why it's come up in looksmaxing discussions.
The two-way relationship with TMJ
Research has linked masseter hypertrophy to bruxism and other parafunctional habits — the same habits behind a lot of TMD. But the relationship isn't only one direction: an existing TMJ disorder can also cause the masseter and surrounding muscles to work harder to compensate for an unstable joint, which can drive hypertrophy as a downstream effect rather than a cause.
What actually reduces it
Since the muscle enlargement is usually driven by overuse rather than being the root problem, treating the underlying clenching or grinding habit is generally the more sustainable approach — see our Bruxism & Overuse Relief program. Botox injections into the masseter are also commonly used to shrink the muscle by reducing its activity, though that's a cosmetic/medical procedure with its own tradeoffs worth discussing with a provider rather than a DIY fix.