Functions of the lateral pterygoid muscle.

The lateral pterygoid, a muscle of mastication has been implicated, with little evidence, in the aetiology of temporomandibular disorders. Three to five percent of the population in developed countries requires treatment for temporomandibular disorders. There is limited information about the normal function of the muscle, which is anatomically divided into a superior and an inferior head. The superior head is involved in clenching, contralateral, ipsilateral, protrusive, retrusive and open-close jaw movements and the inferior head in contralateral, protrusive and opening jaw movements. Recent electromyographic data suggest the muscle participates in fine control of horizontal movements and there are similarities in functional properties between the two heads.