2 All joints are trade-off between mobility and stability Figure 9.1
3 Factors that influence mobility and stability of a joint Articulating surface and surrounding bonesDetermines types of movements possibleBone-hitting-bone can limit movementsJoint capsule and ligamentsCan restrict or permit movementsMuscle that crosses joint or is near jointCan stabilize jointsCan limit movementE.g., hip and knee flex more passively than actively
4 Spine:A series of 24 individual vertebrae + sacrum (5 fused vertebrae) + coccyx (~4 fused vertebrae).Functionally:bears and transmits upper body weight onto the pelvis while permitting movement.Accomplished by being made of many individual bones stacked on one anotherSmall movement between each vert considerable mobility with decent stabilityprotects the spinal cord
5 RegionsCervical — secondary curve—created and maintained by muscle use associated with upright postureThoracic—primary curve—present at birth and maintained by associated bonesLumbar — secondary curve—created and maintained by muscle use associated with upright postureSacrococcygeal—primary curve—present at birth and maintained by associated bonesPresence of Curves places body weight in the correct place for upright posture.Primary curvatures are less mobile, but more stable and less prone to injury.
6 Vertebral Anatomy Body is the weight bearing portion Processes are sites of muscle and ligament attachmentthe pedicle and lamina help create the vertebral foramen through which passes the spinal cord (also protects the cord)Articulating processes help define movements that are possible between adjacent vertebrae
7 Intervertebral Joints nucleus pulposusannulus fibrosusThere are two joints between individual vertebraeJoints between bodies: symphysis—intervertebral discsdisc both absorbs shock and acts as a flexible spacer that allows intervertebral movement.Joint between superior and inferior articulating processes (facets): synovial jointdirection/orientation and shape of the articulating processes defines/determines what kind of movements are possible between vertebra—especially the degree of rotation possible
8 Joints of the spineintervertebral disk--symphisissynovial joint –plane-- between articulating processes
10 Refer to lecture notes for details on the structure and function of intervertebral discs
11 Herniation of disc (rupturing and protrusion of nucleus pulposus) can pinch nerves between the expanded disc and nearby bone structures which creates pressure on the nerve and thus pain and dysfunction.
12 Joint MobilityMobility (types and range of motion) at a joint can be influenced by:shape of articulating bone surfaces and boney structures interfering with joint movement (bone-bone interference)ligaments becoming tight and braking/stopping further movement in a particular directionthe compression of soft tissue (e.g., muscle, adipose) preventing further joint movement.
14 Ligaments of the Spine: Simplified Scheme anterior ligamentsPosterior ligamentslateral ligaments
15 Bones are held in place and supported in much the same way that a pole is supported/held in place by guy-lines/ropes anchoring them into the ground. Bone—which structurally bears/transmits compressive force is supported (i.e., held in place) by fibrous tissue and muscle—tensile structures (the tensegrity model)
16 In extension/hyperextension: SPINAL EXTENSIONIn extension/hyperextension:spinous processes move toward one another and can limit movement on the side being moved toAnterior ligaments become tight and limit/brake movementNote: nucleus pulposus is being pushed anteriorly
17 There are no boney structures of the vertebrae to limit flexion SPINAL FLEXIONIn Flexion:There are no boney structures of the vertebrae to limit flexionPosterior ligaments become tight and act as a brake to flexionNote: the disc is stressed toward the posterior.
18 LATERAL FLEXION (I.E., SIDE BENDING) The transverse processes on the side being flexed toward (ipsilateral) move toward one another and will limit movementthe lateral ligament on the opposite side (contralateral) will become tight to limit movementNote: disc being stressed toward the side being bent away from (contralateral).
19 ROTATIONLargely influenced by orientation of articulating processes and presence/absence of ribs