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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� 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 1,25-dihydroxyvitamin 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 - WadsworthHealthy (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
© 2007 Thomson - Wadsworth
DEXA scan of the left hip
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; “age-related,” “postmenopausal”
� Secondary - disease and drug associated � 2/3 of cases in men
© 2007 Thomson - Wadsworth
Osteoporosis
� Risk factors
� Genetic susceptibility� Family hx� Female sex� Caucasian race� Premenopausal amenorrhea� Physical inactivity� Low calcium and vitamin D intakes
© 2007 Thomson - Wadsworth
Osteoporosis
� Prevention strategies� 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
� 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� 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� 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
� 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