The neutral or ortho-static head position (with horizontal Frankfurter plane) allows healthy TMJ, craniovertebral, cervico-thoracic functions, and a stable occlusion (‘bite’). Rocabado further defined normal cervical lordosis and craniovertebral relationships based on cephalometric measurements. A line connecting the posterior nasal spine to the basi-occiput is called the McGregor’s plane or line. The odontoid plane (OP) is a line extending from apex to the anterior inferior angle of the odontoid process. A normal measurement of the posterior-inferior angle (craniovertebral angle – CV) at the intersection of McGregor’s plane and OP is 101° ± 5° (96–106°). The distance between the basi-occiput and the posterior arch of the atlas is 4–9 mm (less than 4 mm indicates craniovertebral compression). Losing this normal CV angle and assuming a forward head posture also results in loss of healthy cervical lordosis, potentially leading to premature cervical joint degeneration and pain.
With forward head posture, the distance from chin to sternum increases, stretching the hyoid muscles and pulling the mandible back and down. This may result in a retro-inclined profile (posteriorly set chin) and mandibular malformation, as the mandible is held posteriorly during growth. Forward head posture can also contribute to TMJ disc displacement and myofascial pain of the masticatory and cervical muscles.
Forward head posture causes posterior cranial rotation and stretches the infrahyoid muscles, increasing activity in the masticatory muscles and cranial extensors. This often results in overuse, strain, and pain. The muscles of mastication try to maintain a closed mouth position, while the infrahyoid muscles attempt to depress and retract the mandible. This constant “fight” between muscle groups is referred to as parafunction. Proper therapy restores balance by aligning the craniovertebral angle and cervical lordosis on a stable shoulder girdle.
Finding a qualified physical therapist with certifications in managing temporomandibular disorders (TMD) is essential. Therapy can help reduce tension, restore function, and prevent further degeneration by normalizing head posture, cervical lordosis, and muscular balance.
