If there is a spasm in the right lateral pterygoid, which direction will lateral deviation be painful?

When the right lateral pterygoid muscle is in spasm, it has direct implications for movement and associated pain during lateral deviations of the jaw. The lateral pterygoid is responsible for the biting and grinding motions of the jaw, and it plays a critical role in lateral excursions.

If there is a spasm in the right lateral pterygoid, it suggests that this muscle is hyperactive or in a state of tension. Consequently, when the jaw deviates to the left, it requires the right lateral pterygoid to relax and stretch as the left lateral pterygoid contracts to facilitate that movement. This elongation of the spastic right lateral pterygoid during left lateral deviation can lead to significant discomfort or pain due to the increased tension and inability to adequately perform its role.

Thus, lateral deviation to the left will result in pain because it exacerbates the condition of the spastic muscle that is unable to function properly.