Skeletal Considerations for Movement Flashcards
What are 5 functions of the skeletal system?
Leverage
Support
Protection
Storage
Blood-cell formation
Morphology
Shape & structural arrangement of bones and characteristics of the articulations connecting the bones
How is bone size determined?
Bones increase in size from superior to inferior (proximal to distal) due to loads of forces
What is bone tissue made up of?
Minerals
Calcium, phosphate
Resist compression
Extracellular matrix
Type 1 Collagen
Resists tension and add flexibility
Water
Mostly collagen fibers
Osteocyte
Bone cell
Osteoblast
Builds bone
Osteoclast
Breaks down bone/reabsorbs
Architecture of Bone
Cortical Bone
Compact, very dense, outer layer
Cancellous (Trabecular) Bone
Spongy, finger-like, very porous, inner layer
Better at multidirectional stressors
Near end of bones
Epiphysial Plate (“Growth Plates”)
Cartilage turns into bony tissue growing up
Reason people recommend against weight training young
Primary growing end
Where most growth is occurring
Located toward elbow, Radius and Ulna toward wrist, tibia and fibula toward knee
Types of Loading
Compression (Pushing bones together)
Tension (Pulls bones apart)
Shear (Parallel force to surface of object)
Bending (Compression on one side, Tension on the other)
Torsional (Twisting force)
Wolff’s Law
Reabsorption (Response to decreased stress; Osteoclasts)
Deposition (Response to increased stress - Weight bearing; Osteoblasts)
Relationship between Bones and Physical Activity
Bones require mechanical stress to grow and strengthen.
Loading -> Deposition -> Increased Density
Bone Tissue Characteristics (4)
Anisotropic: Directional specific loads determine weight
Viscoelastic: Rate of Loading
Elastic: Stretch and come back to normal
Plastic: Stretch and maintain shape of stretch
Stress
Force/Area
Strain
Change in Length/Angle
Stress - Strain Graph
Bone will remain elastic for until reaching the yield point. Past the yield point the bone is no longer elastic and become plastic. Eventually continuing to have high levels of stress (load) leads to fracture.
Stiffness = Change in stress/Change in strain
Strength = Failure point or load sustained before failure
Stress (Load)
Strain (Deformation)
-Elastic through 3% deformation
Types of Bones Elastic Periods
Ductile: Steep slope, Long elastic period
Brittle: No plastic region, steep slope
Bone: Elastic and Plastic region
Where are bones strongest and why?
Bone is strongest in long axis compression due to Wolff’s Law; Bone response to forces put on it.
Bone Anisotropy Effects on types of bones
Can handle most Stress
Compression
Tension
Shear
Can handle least stress
Shear and torsion almost same around cortical bone
Bones are extremely unique to every individual due to their loading history
Viscoelastic Response
Behavior of bone is dependent on rate load is applied. The slower the load the earlier the fracture; The faster the load the later the fracture.
Bone changes in childhood
Osgood-Schlatter’s disease
Inflammation, bony deposits, or avulsion fracture of tibial tuberosity
Muscle-bone strength imbalance
Rapid growth of femur and tibia places high strain on patellar tendon and tibial tuberosity
Overuse injury
Repetitive stress influence on skeletal structures
Little leaguer’s elbow
Boney changes as an adult
Little length change
Most change in bone mineral density (peak in 30s)
Females: Hormonal Influence
Estrogen – maintain bone minerals (aging effect)
Link between amenorrhea and decreased estrogen – female triad
Osteopenia
Reduced BMD, slightly elevated risk of fracture
Osteoporosis
Severe BMD reduction, very high risk of fracture
What can be done to stop bone loss with age?
Suggest activities with high intensity loads, low repetitions
Going to Failure is important
Stress Fractures
Resorption weakens bone
Deposition occurs too slowly
Results from repetitive muscle forces stressing bone tissue
Any new intensity to the system causes osteoclasts to breakdown bone but later osteoblasts taken over
The third week of training, relax some as there is a larger imbalance of osteoclasts compared to osteoblasts
Avulsion Fracture
Muscle pulls on bone and breaks bone off with it
Happens to younger children
As one gets older you are more likely to tear tendon or muscle itself not bone
Diarthrodial (Synovial) Joints
Articular cartilage
-Poor blood supply, nourished by synovial fluid
-Viscoelastic and responds to shear well
Capsule
Synovial membrane – lubrication
-Non-Newtonian Fluid
-Frictional characteristics change depending on speed of joint movement
Ligament
-Loading increases ligament strength and stiffness
Diarthrodial Joints
Closed packed vs loose packed
Closed packed – maximum contact
-Stable
-Ligaments tense, greater injury potential
Loose packed – less contact
-Less friction
-Greatest volume
-Position of choice if effusion is present
Anatomical position is in closed pack position (except shoulder)
Planes of Motion
Sagittal
Frontal (Coronal)
Transverse (Horizontal)
Oblique
Osteokinematics
Rotational motion of one bone relative to another
-Flexion/Extension, Abduction/adduction, Internal/External
Arthrokinematics
Motions between surfaces within the joint
-Roll, slide, spin
Note: Mechanisms can change with change in fluid amounts
Concave vs Convex
Concave (depression)
Convex (round)
Convex-Concave Rule
When convex surface moves on concave, roll and slide occurring opposite directions
Knee: Tibia is concave, Femur is convex. Femur is moving during squatting – Convex (forward) moves on concave (backwards)
Osteo and Arthro in opposite directions
When concave surface moves on convex, roll and slide occur in the same direction. Ex: Knee extension
Osteo and Arthro in same direction
A bone will exhibit residual strain when load is removed while the bone is in the elastic region of the stress-strain curve (True/False)
False, no that’s an example of plastic
The epiphysis is primarily composed of what type of bone?
Cancellous Bone
The structural organization of cortical bone allows for the greatest resistance to which type of loading?
Compression
A tissue’s deformation in response to a sustained load will gradually increase over time. What term is used to describe this mechanical property?
Creep
Frontal plane motion occurs about an axis running in which direction?
Longitudinal
Glenohumeral joint flexion is an example of an arthrokinematic motion. (T/F)
False, that’s an example of osteokinematics
What is Young’s Modulous? What does a steeper slope indicate?
Stress/Strain
The slope of the linear region of the stress-strain curve is steeper (i.e. higher Young’s modulus)
