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Musculoskeletal System
KNH 413
Skeletal System
 Cartilage, ligaments, tendons, bones
 Metabolically active cells and tissue
 Continual state of change
Skeletal System
 Cartilage – flexible yet firm connective tissue consisting
of cells and collagen fibers
 Chondroblasts/chondrocytes – cells
 Collagen – fibrous protein, most common protein in the
body
 Chondroitin sulphate – most common polysaccharide of
cartilage
Skeletal System
 Bone – osseous tissue
 Organic – mineralized or calcified by inorganic component;
flexibility
 Inorganic - hydroxyapatite; stiffness, weight bearing
 Ready source of calcium and phosphorus for extracellular
fluids
 Hydroxyapaptite (99%)
 Readily available pool (1%)
Skeletal System
 Bone
 Abnormalities in serum calcium critical
 Hypocalcemia – excessive excitability of the nervous system,
tetany , respiratory arrest, convulsions
 Hypercalcemia – fatigue, depression, metal confusion,
anorexia, nausea, vomiting, constipation, hypercalciuria
Skeletal System
 Cells of Osseous Tissue
 Osteogenic cells – stem cells that differentiate into
osteoblasts
 Osteoblasts - bone-building cells
 Osteocytes – mature osteoblasts, majority of cells in bone
 Osteoclasts – bone-removing cells that secrete HCl; bone
resorption
Skeletal System
 Skeletal growth and development
 Continual state of change; linear and circumferential
growth, and in response to changes in forces applied to
them - remodeling
 Osteoclasts remove bone from low-stress areas, osteoblasts
lay down new bone in high-stress areas
Skeletal System
 Cortical bone
 Dense, outer surface of most bones, shafts of
long bones, and caps over end of long bones
 75% of skeletal weight
 Trabecular bone
 Loosely organized with a sponge-like
appearance; lattice-like pattern
 “Ends” of long bones, primary bone of vertebrae,
pelvis, sternum, scapula
 25% of skeletal weight
© 2007 Thomson - Wadsworth
© 2007 Thomson - Wadsworth
© 2007 Thomson - Wadsworth
Skeletal System
 Hormonal control of bone metabolism
 Calcium and phosphorus homeostasis
 Cortisol, growth hormone, thyroid hormones
 Primary regulators: parathyroid hormone (PTH), calcitonin,
vitamin D
Skeletal System
 PTH – increases blood calcium when low
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Increase in osteoclasts and bone resorption
Inhibition of collagen synthesis and bone deposition
Calcium resorption by kidneys
Final step in vitamin D synthesis, enabling intestinal
absorption of calcium
Skeletal System
 Calcitonin – decreases blood calcium when high
 Inhibits activity of osteoclasts
 Stimulates osteoblasts
 Reduces renal reabsorption of calcium and phosphate
Skeletal System
 Vitamin D – increases blood concentrations of calcium
and phosphorus
 Promotes their absorption in GI
 Promotes reabsorption by kidneys
 Stimulates osteoclast formation and release of calcium and
phosphorus from bone
Skeletal System
 Vitamin D –
 Ergocalciferol - dietary
 Cholecalciferol – dietary, exposure to
sunlight
 Both biologically inactive until
modified by liver and kidney to 1,25dihydroxyvitamin D
© 2007 Thomson - Wadsworth
Osteoporosis
 Decreased bone mineral and organic matrix which
weakens bones, making them more susceptible to
fracture and pain
 Bone strength reflects:
 Bone density
 Bone quality
© 2007 Thomson - Wadsworth
Healthy (L) and osteoporotic (R) trabecular
bone
Osteoporosis
 Diagnosis
 Measures of bone mineral density (BMD)
 DXA – dual-energy x-ray absorptiometry
 “T-score” – comparing patient’s BMD to healthy young
reference population
 BMD assessed at hip and lumbar spine
 See WHO criteria
DEXA scan of
the left hip
© 2007 Thomson - Wadsworth
Osteoporosis
 Diagnosis
 Others:
 Quantitative ultrasound of the heel used in conjunction
with risk assessment – useful for screening
 Osteopenia – bone mineral density is low but not low
enough to be classified as osteoporosis, although
fracture risk is increased
Osteoporosis
 BMD increases rapidly during growth spurt (ages 11-14 y)
 Maximum density reached in late 20s or 30s
 Females lose BMD at faster rate than men
 Rate of loss increases during menopause
Osteoporosis
 Fractures
 Most common sites: hip, spine, wrist
 Kyphosis – unnatural curvature of back, and loss of height
d/t compression fractures of spine
 Hip fractures have severe impact on morbidity and
mortality
 20% die within first year, 20% end up in nursing homes
Osteoporosis
 Etiology
 Primary – disease of elderly, cumulative impact of bone
mineral loss and deterioration of bone with age; “agerelated,” “postmenopausal”
 Secondary - disease and drug associated
 2/3 of cases in men
© 2007 Thomson - Wadsworth
Osteoporosis
 Risk factors
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Genetic susceptibility
Family hx
Female sex
Caucasian race
Premenopausal amenorrhea
Physical inactivity
Low calcium and vitamin D intakes
© 2007 Thomson - Wadsworth
Osteoporosis
 Prevention strategies
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Risk reduction in adolescence and early adulthood
Adequate calcium and vitamin D intake
Weight-bearing exercise
Fall prevention
Smoking cessation
Avoidance of excessive alcohol intake
© 2007 Thomson - Wadsworth
Osteoporosis
 Calcium
 Maintenance of serum calcium levels to combat
bone resorption
 Achieve peak bone mass and minimize bone
mineral loss
 Lower intakes of animal protein, sodium, caffeine
 Increased consumption of fruits, vegetables,
legumes, whole grains
 More physical activity
 Sun exposure
Osteoporosis
 Calcium
 Consume calcium-rich foods
 Calcium-fortified foods
 Calcium supplements
 Calcium carbonate – least expensive, taken with meals, not at
the same time as iron
 Calcium citrate – taken any time
 Calcium with vitamin D
 Avoid dolomite and bonemeal – lead contamination
 Divided doses to improve absorption
© 2007 Thomson - Wadsworth
Osteoporosis
 Vitamin D
 Overt deficiency – rickets in children, osteomalacia in adults
 Insufficiency found in dark-skinned, older, in northern
latitudes (above 40 degree N)
 Supplementation with vitamin D and calcium
 Fortified dairy products
 Exposure to adequate sunlight
Osteoporosis
 Physical activity
 BMD increases with weight-bearing or impact-type activity
 Very high levels can be detrimental if oligomenorrhea or
amenorrhea present
Osteoporosis
 Cigarette smoking
 Lower BMD, increased bone mineral loss, increased risk of
fractures
 Nicotine and cadmium toxic to osteoblasts
 Reduced intestinal calcium absorption
 Lower intakes of vitamin D, and lower serum vitamin D
Osteoporosis
 Alcohol
 Decreased BMD, reduced bone formation, increased risk of
fractures
 Increased calcium and magnesium losses
 Adversely impacts vitamin D and overall nutritional status
 Increased risk of falls
Osteoporosis
 Phosphorus – essential for bone formation
 Carbonated soft-drinks have negligible effect on calcium
excretion
 High protein or sodium - increase urinary calcium losses
 Potassium, magnesium, fruits, vegetables associated with
higher BMD
Osteoporosis
 Medical management
 Risk factor modification
 Dietary treatment
 Drug therapy
© 2007 Thomson - Wadsworth
Osteoporosis
 Pharmacologic prevention and treatment
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Estrogens/ hormone therapy
Selective estrogen receptor modulators (SERMs)
Bisphosphonates
Teriparatide (synthetic PTH)
Drug-nutrient interactions
Paget Disease
 Localized, progressive, crippling disorder of bone
remodeling d/t overactive osteoclasts and bone
resorption followed by rapid formation of new bone
which is structurally inferior
 Bowing, deformity, fracture, poor healing
 Upper femur, pelvis, vertebral bodies, skull, tibia
 Genetic and viral factors
 Adequate intake of vitamin D and calcium
important
Rickets
 Inadequate maturation and
mineralization of bone in children
 d/t vitamin D deficiency
 Risk factors – Table 27.10
 Symptoms: lethargy, weakness,
growth stunting, enlargement of
ends of long bones and ribs,
abnormally shaped thorax, bowing
of legs
Rickets
 Prevention
 Exclusively breast fed infants should receive supplement of
200 IU vitamin D
 Fortified infant formulas
 If receiving less than 500 mL/day, should be given multivitamin
supplement
 After 1 year – vitamin D-fortified cow’s milk
Rickets
 Treatment
 Balanced, age-appropriate diet
 Adequate vitamin D, calcium, phosphorus
Osteomalacia
 Organic matrix of bones inadequately mineralized in
adults
 Muscular weakness, bone pain, deformities of ribs,
pelvis, legs
 d/t vitamin D deficiency, impaired D action, calcium
deficiency, hypophosphatemia
Osteomalacia
 Treatment
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Address underlying cause
Multivitamin supplementation
Calcium supplementation
Pharmacological doses of vitamin D
Arthritic Conditions
 Affect joints, tissues surrounding joints, and connective
tissues
 Osteoarthritis, rheumatoid arthritis, gout (affecting all
ages)
 Risk factors - modifiable:
 Overweight
 Joint injuries
 Infections
Arthritic Conditions
 Risk factors - nonmodifiable:
 Female sex – 60% of cases
 Age
 Family hx
Osteoarthritis
 Most common, leading cause of physical
disability
 Disease process involving all structures of
the joint
 Loss of load-bearing articular cartilage
 Inflammation
 Joint pain, stiffness, limited movement, wasting
of periarticular muscles, joint instability and
deformity
Osteoarthritis
 Major risk factors
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Age
Female sex
Family hx
Major trauma to joint or soft tissue
Repetitive joint stress related to occupation
Obesity
Osteoarthritis
 Treatment
 Reduce joint inflammation & pain, maintain mobility,
minimize disability
 Improve body posture
 Proper footwear
 Weight reduction
 Periodic rest of affected joint
 Heat
 Physical activity/ therapeutic exercise
Osteoarthritis
 Treatment
 Drug therapy – pain relief
 NSAIDs
 Glucosamine and chondroitin
Rheumatoid Arthritis
 Chronic inflammatory disease; synovial membrane
becomes inflamed resulting in swelling, stiffness, pain,
limited range of motion, joint deformity, disability
 Characterized by periods of exacerbation and remission
 Autoimmune response
Rheumatoid Arthritis
 Inflammation of joints of hands, wrists, knees, & feet
results in warmth, redness, swelling, stiffness, and pain
 Inflammation results in thickening of synovial membrane
known as pannus – see Fig. 27.10
 Enzymes from pannus digest adjacent bone and
cartilage
Rheumatoid Arthritis
 Treatment
 Reduce pain and inflammation, protect joint, maintain
function, control systemic infections
 Pharmacological agents: NSAIDs, glucocorticoids,
immunosuppressives, DMARDs
Rheumatoid Arthritis
 Diet
 Increase consumption of fruits and vegetables/
antioxidants
 Include sources of EPA and DHA
 Fish oil supplementation
 Exclusion of red meats, dairy, cereals, wheat gluten
 Evaluate and test for food allergy
Gout
 Inflammatory disease resulting in swelling, redness,
heat, pain, and stiffness in affected joint
 d/t elevated serum concentrations of uric acid,
formation of uric acid crystals
 End product of purine (adenine and guanine) metabolism
Gout
 Hyperuricemia results from overproduction
of uric acid, inadequate elimination by the
kidneys, or combination
 Most painful arthritic condition
 Risk factors: genetics, male sex, older age,
overweight, excessive alcohol consumption,
eating foods rich in purines, exposure to
lead, certain drugs
Gout
 Most commonly affects great toe, instep, ankles, heels,
knees, wrists, elbows, fingers
 Rapid occurrence
 Sudden severe pain; swelling; shiny, red skin around
joint; extreme tenderness
 Typically resolves 5-10 days, may reoccur
Gout
 Acute attack may be precipitated by:
 Excessive exercise
 Certain medications: aspirin, diuretics, nicotinic acid,
cyclosporine, levodopa
 Purine-rich foods
 Excessive alcohol consumption
 Crash dieting
© 2007 Thomson - Wadsworth
Gout
 Treatment:
 NSAIDs, glucocorticoids, colchicine
 Treat uricemia
 Lifestyle modifications
Fibromyalgia
 Chronic musculoskeletal disorder characterized by
widespread muscle pain, joint stiffness, disturbed sleep,
fatigue, headache, cognitive and memory problems,
paresthesias, & tender points
 Not crippling, deforming, or disabling
 Etiology unknown
Fibromyalgia
 Dg by ruling out other potential causes of symptoms
 Hx of pain that is widespread for at least 3 months
 Excessive tenderness or pain with pressure to at least 11 of
18 tender points
© 2007 Thomson - Wadsworth
Fibromyalgia
 Treatment
 Improve sleep, treat depression, anxiety and pain, improve
ability to relax
 Antidepressants, counseling
 Regular physical activity
 Cognitive behavioral therapy
 Intensive patient education
Fibromyalgia
 Diet
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Avoidance of certain foods has worked for some
Low-sodium, uncooked vegan diet has shown promise
? MSG avoidance
Lack of sound scientific evidence at this time