TMJ, Posture, Gait

What are the joint surfaces in the TMJ articulation?

• convex articular eminence of temporal bone

• concave articular disc

• convex condyle of mandible

What is the superior and inferior joint of the TMJ and what motions occur at each?

superior:

• convex articular eminence of temporal bone

• concave articular disc

• motion: gliding joint

inferior:

• concave articular disc

• convex condyle of mandible

• motion: hinge joint

Describe the arthrokinematics of opening your jaw (jaw depression)

• Phase I: inferior joint: hinge

  • posterior roll of mandibular condyle (more like spin) on articular disc

• Phase II: superior joint: gliding

  • anterior translation of articular eminence on disc

What motion is necessary for full depression of the mouth? How much is this relatively?

• translation: gliding between articular eminence and disc

• 40 mm

Describe the arthrokinematics of closing your jaw (jaw elevation)

• Phase I: posterior translation at superior joint (articular eminence and disc)

• Phase II: anterior rotation of at inferior joint (mandibular condyle and disc)

Describe the arthrokinematics of lateral deviation of the jaw

• ipsilateral: clockwise spin of mandibular condyle

• contralateral: anterior translation of mandibular condyle

Describe the arthrokinematics with protrusion

• anterior/inferior translation of mandibular condyle and articular disc

• no rotation!

Describe the arthrokinematics with retrusion

• posterior/superior translation of mandibular condyle and articular disc

• no rotation

Between which joint (superior or inferior) is the articular disc of the TMJ more loosely connected? What is the result of this?

• superior joint: articular eminence and disc

• result: more motion; disc freer to move

Which ligament of the jaw limits excessive anterior translation?

• TMJ ligament

• sphenomandibular ligament

What muscles are involved with elevation of the jaw?

• masseter

• temporalis

• medial pterygoid

What muscles are involved with depression of the jaw?

• lateral pterygoid

• digastric

• suprahyoid/infrahyoid

What muscles are involved with lateral deviation of the jaw?

• ipsilateral: temporalis

• contralateral: lateral pterygoid

• masseter

What is the retrodiscal tissue found within the TMJ?

• tissue that attaches posteriorly to the TMJ

• superior band: allows for anterior translation

• inferior band: limits anterior translation

What structures attach anteriorly to the TMJ and what is their function?

• joint capusle

• lateral pterygoid tendon

• limit posterior translation of disc

What is the main function/advantage of the articular disc of the TMJ?

• increase congruency of joint surfaces

• more flexible and more motion

What is considered a functional opening of the TMJ?

two fingers/2 PIP

What is bruxism?

• excessive teeth grinding

• causes compression from lower teeth elevating

• treatment: mouth guard

What is a sign of hyper mobility of the TMJ?

• palpation of a hollow space behind the condyle during depression

Describe the pathology of dislocation in a TMJ patient (how patient presents, how this happens)

• patient can’t close mouth voluntarily

• condyle and disc translate too far and get stuck

• cause: articular eminence with a slope

Describe the pathology of disc displacement with reduction in a patient (how patient presents, how this happens)

• clicking sound when patient opens and closes the mouth

• cause: disc gets in the way with depression

• treatment: small bites; only open mouth enough for spin but no translation

What are the functions of mechanoreceptors and what happens when they are damaged?

• can be either thick or thin slow or fast adapting

• function: proprioception; sense change in body position and communicate this to the brain

• can adapt to movement if it is repetitive

• when damaged, stability is greatly affected

What is the function of muscle spindles?

• respond to muscle stretch and cause reflexive contraction

• example: when falling forward, muscle spindles sense stretch and cause muscles to contract to bring you back

What is the function of golgi tendon organ?

• sense when a muscle has too much tension and causes reflexive relaxation

What are some fixed support strategies for maintaining balance?

• ankle synergy

  • ankle DF contract when falling backward to bring tibia back over ankle

• hip synergy

  • hip extensors contract when falling forward to bring pelvis/femur back

What are some change in support strategies for maintaining balance?

• stepping: forward, backward, to the side

• grasping

• increase BOS so COM and LOG fall within the base

Explain the condition of hammer toes: patient presentation, potential causes, and effects

• MTP: hyperextended; PIP: flexed

• flexors unopposed, weakness of toe extensors and lumbricals

• less push-off force, callus formation, narrow BOS, less stability

Explain the condition of pes planus: patient presentation, potential causes, and effects

• “flat feet”, low medial arch, over-pronation: calc everted, talus PF/AD in weight-bearing

• tibial MR, genu valgus

Explain the condition of pes cavus: patient presentation, potential causes, and effects

• high medial arches, foot in supination

• lengthening/stretching of lateral ankle ligaments, higher incidence of inversion/lateral ankle sprains, limits foot’s ability to shock absorb

Explain the condition of scoliosis: patient presentation, potential causes, and effects

• lateral deviation of the spine

  • structural = can’t be fixed unless with brace/surgery

  • functional = leg length difference

• genetics, changes in bone and soft tissues that can’t be corrected actively, adaptations of the spine that can be corrected (e.g. disc herniation, leg length difference)

• LBP, decreased expansion of the ribs, muscle adaptation: shortening on side of concavity, lengthen on side of convexity, facet joint pain

How does pregnancy affect posture and what are the effects/treatment ideas?

• ligament laxity leads to increased anterior pelvic tilt/lordosis

• causes anterior shear force which leads to LBP

• treatment: strengthening rectus abd, lats, glute max