Jaw Deviation vs Jaw Deflection: What’s the Difference
When you open your mouth normally, the lower jaw (mandible) should move straight and symmetrically. Sometimes you’ll see it drift or shift, and there are two related—but distinct—patterns: deviation and deflection.
Deviation means the jaw moves off to one side during opening, but as you get near full opening, it returns to the mid-line before fully opening.
Deflection means the jaw shifts off to one side as it opens and does not return to the mid-line even at full opening. It stays shifted toward one side.
Anatomical and Functional Reasons
The temporomandibular joint (TMJ) is formed by the mandibular condyle sitting in the temporal bone socket, separated by an articular disc. Opening is a two-phase process: first rotation, then translation (sliding). Muscles, ligaments, and the disc guide the movement.
Key muscles involved include the lateral pterygoid, masseter, and temporalis. Smooth jaw movement depends on these muscles coordinating properly.
In deviation, one side may open or translate more slowly, but eventually both sides even out. This can be due to mild imbalance or early dysfunction.
In deflection, there is usually a restriction—such as disc displacement, capsular tightness, or significant muscle imbalance—that prevents the jaw from returning to the center.
Poor neck posture or cervical alignment can contribute, since cervical muscles and posture influence jaw mechanics.
Physiotherapy Management
Motor Control and Stability
Mirror-guided opening and closing to retrain symmetry.
Isometric holds with gentle resistance to balance both sides of the jaw.
Controlled opening, starting small and gradually increasing range.
Stretching and Soft Tissue Release
Gentle stretches for tight jaw muscles (masseter, temporalis, pterygoids).
Massage or self-release to reduce tension.
Joint and Disc Management
Mobilizations by trained clinicians may improve translation if restricted.
Specific exercises to encourage smooth condylar movement.
Cervical Alignment and Posture
Posture training: chin tucks, neutral head position.
Strengthening deep neck flexors, stretching overactive neck muscles.
Habit awareness: avoid clenching, prolonged wide opening, poor sleep posture.
Pain and Load Management
Avoid very wide bites or yawns during painful phases.
Use bite splints if recommended.
Modify activities that overload the jaw until stability improves.
Example Program
Mirror-guided slow opening: open and close in front of a mirror, keeping chin mid-line.
Resisted stability holds: gently resist jaw opening to the side that tends to deviate, 5-second holds.
Tongue rest posture: tongue on the roof of the mouth, teeth slightly apart, jaw relaxed.
Gentle self-massage of jaw muscles for 30 seconds each side.
Neck posture reset: chin tuck, ears over shoulders, 10-second holds repeated several times daily.
Key Takeaways
Deviation suggests mild imbalance; deflection suggests structural restriction or disc involvement.
Physiotherapy focuses on motor control, stability, posture, and pain management.
Combining jaw retraining with cervical alignment strategies provides the best outcomes.
References:
De Leeuw, R., & Klasser, G. D. (2018). Orofacial pain: Guidelines for assessment, diagnosis, and management (6th ed.). Quintessence Publishing.
Okeson, J. P. (2019). Management of temporomandibular disorders and occlusion (8th ed.). Elsevier.
National Center for Biotechnology Information. (2020). Temporomandibular Joint Syndrome. In StatPearls [Internet]. StatPearls Publishing.
Physiopedia. (n.d.). Physiology and biomechanics of the temporomandibular joint.
