Lesson 1.2: How We Move

The spine moves from the top down and the bottom up and meets in the middle at the thoracic spine. The cervical and lumbar spine move separately but influence each other through the dura and the spinal muscles that run the length of the spine. To have full thoracic movement, there must be full cervical and lumbar movement.

The upper quadrant is made up of the cervical and thoracic spine, the tempro-mandibular joint (TMJ), the shoulder, the elbow and the wrist and hand. Each part works together to create full, functional upper body movement. This is defined as the upper quadrant kinetic chain.

Neck pain is a simple concept but a rather complicated system. There are seven cervical vertebrae, each able to translate along three axes and rotate about these three axes. There are as many as six to ten joints between each cervical vertebra.

Beginning at the very top of the spine, the atlanto-occipital and atlanto-axial joints do not move in isolation. Rather, the joints of the occiput, atlas (C1) and axis (C2) move in conjunction with each other. The atlanto-occipital joints are challenged to hold the head upright on the cervical spine yet allow for mobility. The atlas sits like a washer between the skull and the axis allowing rotation of the head. The axis accepts the load of the head and atlas and transmits that load to the remainder of the cervical spine.

Cervical lateral bending occurs at and below C3. During lateral bending of the head to the left, the atlas rotates to the right while the axis rotates to the left. This combination of movements occurs because side-bending exerts a downward load on the ipsilateral articular pillar. Flexion and extension in the lower cervical spine are always a combination of anterior or posterior translation and rotation in the sagital plane, as the cervical facets are oriented in the transverse plane.

The suboccipital muscles are deeply situated posterior below the occipital region of the head. C1-2-3-4 is the origin of the levator scapulae muscle that also attaches to the scapula. The cervical plexus is formed by the union of the ventral rami of C1 to C4 and supplies adjacent muscles including the longus coli and the longus capitis muscles.17 The spinal accessory nerve from the ventral rami of C2-3 and C3-4 travels to the sternocleidomastoid muscle. C4-5 and C5-6 nerve roots innervate the infraspinatus and all the rotator cuff muscles. The greater occipital nerve pierces the semispinalis capitis muscle on its way to innervating skin at the back of the head. There are many sensory nerves that arise from this plexus to innervate the skin of the neck and the posterior part of the head.

The thoracic spine is a transition zone for movement. It takes fifteen degrees of back extension to have full arm elevation and the ability to take a full, deep breath, as back extension allows for full rib mobility and muscle tone. In general, the thoracic spine exhibits less segmental mobility than the cervical or lumbar regions. There are twelve thoracic vertebrae with up to twelve articulations each with the ribs, transverse processes, adjacent verterbral bodies and indirectly with the sternum.

The vertebrae act like tripods that drop into flexion when stability is needed. Flexion and extension at the thoracic spine are limited due to the vertical alignment of the thoracic facets. The inferior facet of the vertebra above can glide only slightly anterior on the superior facet of the vertebra below. Because the thoracic facets lie close to the frontal plane, the articular surfaces provide little limitation to axial rotation. Lateral bending is also abundant at the thoracic spine because of the front plane alignment of the facets. 

The rhomboid major and minor muscles originate at the vertebral bodies of C7-T1-2-3-4-5 and the scapula. The rhomboids help to control movement of the upper quadrant. The muscle that pass between two adjacent ribs are the intercostals. These muscles act as supporters of inspiration and expiration during breathing. Respiration requires an increase in size of the thoracic cavity, and therefore an upward movement of the ribs.

Mouth opening combines rotation about a medial-lateral axis with protrusion in the transverse and sagittal planes.  Motion of the tempromandibular joint (TMJ), when opening the jaw, begins with rotation and is followed by translation. Normal movement of the TMJ requires precise synchronization between the movement of the mandible and the movement of the intraarticular disc. When chewing, the mandible is cyclically opening and closing, requiring repeated anterior and posterior gliding.

The TMJ lines up with C1.  Head and neck posture contribute significantly to the pathomechanics of the TMJ. The movement of the cervicothoracic joints significantly influences TMJ movement.

The shoulder complex is held on to the skeleton by only one joint, the sterno-clavicular joint. Full shoulder movement involves not only the shoulder but the thoracic as well. The glenohumeral joint provides 120 degrees of the range of motion of arm elevation. The thoracic spine allows for the remaining 60 degrees of shoulder motion. Not only does the ipsilateral thoracic spine contribute to shoulder movement, but also the contralateral.

Evolution of human movement to bipedal resulted in shoulder muscles that need to position and support a scapula. The glenohumeral joint is no longer primarily for weight bearing and is free to move 360 degrees.  The scapula is a flat bone whose primary function is to provide a site for muscle attachment for shoulder function. The scapula is only along for the ride. A total of fifteen major muscles acting at the shoulder attach to the scapula. The scapula-humeral muscles provide motion and dynamic stabilization to the glenohumeral joint.

The suprascapular nerve from C5-6 innervates the supraspinatus and infraspinatus muscles.17 The teres minor, deltoid, and biceps brachii muscles are innervated by the axillary nerve from C5-6.

The elbow is a saddle joint with the ulnar bone wrapping around the humerus to allow flexion, extension, varus and valgus movements. The radial head is held on to the ulna by the annular ligament. Motion of the distal radioulnar joint is linked to the motion of the proximal radioulnar joint. Pronation and supination occur simultaneously at these two joints. Weight-bearing at the elbow produces force into the ulnar bone while the radius takes the load with weight bearing at the wrist. The diagonal orientation of the interossious membrane fibers allows the load to be transmitted from the radius to the ulna and into the elbow.

The ulnar nerve wraps around the medial epicondyle of the humerus as it travels across the wrist into the hand. The median nerve sits within the carpal tunnel but also runs through the muscles of the proximal forearm and around the elbow.The radial nerve lies against the humeral shaft in the radial groove.

Although the radiocarpal joint is the most familiar joint of the wrist, the motion of the wrist also comes from the midcarpal and intercarpal joints. There are eight carpal bones arranged roughly into two rows, proximal and distal. The proximal row contains the scaphoid, lunate, trapezium, and pisiform bones. The distal row contains the triquetrum, trapezoid, capitate and hamate bones.

The distal surfaces of the carpal bones are irregular, forming multiple articular surfaces for the proximal surfaces of the articulating metacarpal bones. These variations in articular surfaces result in considerable variety in the motion and stability available throughout the carpal bones. 

Flexion takes place almost exclusively at the radiocarpal joint. Extension takes place almost exclusively at the midcarpal joints. Supination of the hand and forearm depends on the ulnotriquetral joint and distal radioulnar joint. Movement at the distal radioulnar joint must be free to allow voluntary movement of pronation of the hand and forearm. Supination and pronation are also dependent on the movement at the ulna-humerus joint.

Thumb movement depends largely on the mobility of the carpometacarpal (CMC) joint. Flexion and extension of the CMC joint occurs in the plane of the palm. Medial rotation of the thumb’s CMC joint occurs along with either flexion or abduction, while lateral rotation occurs with extension or adduction. The CMC joint is a saddle joint and is capable of almost 360 degrees of motion, almost as much as the glenohumeral joint.

The lower quadrant is composed of the lumbar spine, the pelvis, the hip, the knee and the ankle and foot. All components move together to create full, functional lower body movement. This is defined as the lower quadrant kinetic chain.

All movement begins at the pelvis. The sacroiliac joint can move 47 different ways and there are three axis of rotation through the pubis symphysis.

When the sacrum goes forward the fifth lumbar vertebra extends backward. When the sacrum goes backward, the fifth lumbar vertebra flexes forward. At the fourth and the fifth vertebra there is a ligament that connects to the ilium, which allows pelvic movement without the lumbar and vice versa.

A primary function of the facet joint is to guide segmental motion. In the lumbar spine the facet joint planes orient roughly sagitally. Therefore, movements into flexion and extension have larger excursions than movements into rotation or side bending.  The second sacral vertebra marks the center of gravity of the human body in the erect, standing posture. Due to the anatomical adaptations that have occurred in response to upright posture, the lumbo-pelvic region bears much of the human body’s weight. The trunk and ground forces working on the human body converge at the lumbar and pelvis.

The hip joint is a ball and socket joint capable of flexion, extension, abduction, adduction and rotation. Full pelvic movement is necessary for normal hip range of motion. Pelvic motion is dependent on lumbar motion so mobility of the lumbar spine also influences hip movement. Full hip movement depends on full mobility of the lower quadrant kinetic chain.

The knee is capable of moving in flexion, extension, recurvatum and tibial rotation. Full tibial rotation is required before full knee extension, recurvatum and flexion is accessible. Recurvatum is normal and necessary for full functional knee movement.

The knee includes four articulating surfaces between the femur and the tibia, each with a different radius of curvature. These differences help produce the combination of rotation and translation that accompanies knee flexion and extension. Full knee range of motion occurs only with full pelvic, hip and ankle mobility.

There are 46 bones in both feet combined. This is 25 percent of the bones in the body.  There are two rows of cuneiforms that create forefoot pronation and supination. Pronation is a normal movement of the foot and is necessary for full mobility. There is a difference between a pronated foot and a dropped arch. A dropped arch is a laxity of the posterior tibial tendons holding up the navicular bone and surrounding cuneiforms. Attempts to fix pronation with an orthotic is common, but may not be necessary as pronation is a normal motion.

We are the most vulnerable where the second metatarsal and the cuneiforms meet. This is the tightest part of the forefoot with limited mobility and many articulations. We are also vulnerable as the talus rolls forward to create full plantar flexion within the distal tibio-fibular notch. This is because the anterior aspect of the talus is wider than the posterior portion and when it rolls forward into the tibio-fibular notch it creates increased space and an increased chance for a joint restrictions.