Masseter Muscle Hypertrophy

Enlarged Jaw (Masseter Muscle Hypertrophy)

If you have a square jaw, you may be affected by Masseter Muscle Hypertrophy (MMH).

Your masseter muscles are located on the left and right sides of your face, running vertically between your jaw angle and cheekbones. These muscles allow you to open and close your jaw, playing a vital role in chewing and speaking.

Hypertrophy is a medical term for an enlargement of organs or tissues.¹ If you have MMH, your facial muscle cells grow dramatically, giving the jaw and lower face a square, angular, and often asymmetrical shape.

What Causes MMH?

MMH can have a number of causes. If you clench or grind your teeth (bruxism), are affected by a misalignment of the teeth (malocclusion), or have a condition that affects jaw movement (TMJ Disorder), you may develop MMH.²

MMH can also develop with no known cause (idiopathic MMH).

MMH Symptoms

People with MMH may experience jaw pain, but others may be affected without feeling any discomfort.² MMH is often diagnosed after a patient seeks medical care for the visible signs of their condition.

MMH is largely a cosmetic condition, but can nonetheless cause embarrassment and self-consciousness. Women tend to be more concerned about the angular or square facial appearance of MMH as it is often perceived as masculinising. There are also cultural and racial preferences for the ideal female facial shape: an oval or heart-shaped facial contour is typically more highly regarded than a square or round facial contour.

Treating MMH

There are a number of cosmetic procedures available to those with MMH. These range from cosmetic surgery³ to less invasive non-surgical jaw reduction procedures.

Dermatologists are helping to develop safer, more effective, and less invasive MMH treatments through clinical trials (also known as “research trials” or “research studies”). If you or someone you know is affected by the appearance of MMH, consider a research trial of a potential treatment.