The lateral pterygoid muscle: some anatomical, physiological and clinical considerations.

The lateral pterygoid muscles make a unique contribution to jaw movement control by virtue of their attachment to temporomandibular disc and condyle. Their highly specialized function is reflected in their extrafusal muscle fibre composition and the paucity of muscle spindles to provide proprioceptive feedback. It is likely (studies in progress) that their histochemical spindle intrafusal fibre composition is also unique. The superior and inferior portions of the muscle have defined functional roles. The superior portion primarily contributes to the apposition of disc, condyle and eminence in jaw closing, whilst the lateral portion primarily contributes to jaw opening. In this review, possible control mechanisms for this muscle are proposed. As well, the role of the superior head in influencing rotation and translation of disc and condyle and the relationship with internal derangement and temporomandibular dysfunction is considered.