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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

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

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

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

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

Osteoporosis

� Risk factors

� Genetic susceptibility� Family hx� Female sex� Caucasian race� Premenopausal amenorrhea� Physical inactivity� Low calcium and vitamin D intakes

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

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

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

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


� 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


� Treatment� Reduce pain and inflammation, protect joint, maintain

function, control systemic infections� Pharmacological agents: NSAIDs, glucocorticoids,

immunosuppressives, DMARDs


� 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

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

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

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