319: DEGENERATIVE DISORDERS OF THE MUSCULOSKELETAL SYSTEM

What is constant in bone health?

Bone remodeling (continuous cycle of resorption and formation)

What mineral is bone health most dependent on?

Calcium

What hormones regulate calcium and bone metabolism?

Parathyroid hormone (PTH), calcitriol (vitamin D), and calcitonin

What does parathyroid hormone (PTH) do in bone health?

Increases blood calcium by stimulating bone resorption

What is calcitriol?

The active form of vitamin D that increases calcium absorption in the gut

Works with PTH

What does calcitonin do?

Released by thyroid and lowers blood calcium by promoting bone formation and reducing bone resorption

What sex hormones support bone health?

Testosterone and estrogen

How do sex hormones affect bone health?

They help maintain bone density and reduce bone loss

What is mechanical stimulation in bone health?

Physical stress/weight-bearing activity that stimulates bone formation and strengthens bone

What are synarthrosis joints?

Immovable joints (no mobility)

What are diarthrosis joints?

Freely movable joints; most movement in the body (synovial joints)

What are amphiarthrosis joints?

Slightly or moderately movable joints

What is arthropathy?

Any joint disorder

What is arthritis?

Inflammation of a joint

What is monoarticular arthritis?

Arthritis affecting one joint

What is polyarticular arthritis?

Arthritis affecting multiple joints

What do chondrocytes do?

Produce and maintain cartilage

What happens to cartilage with aging?

Cartilage is gradually lost, reducing joint cushioning

What provides cushioning in joints?

Articular cartilage and synovial fluid

What causes articular cartilage breakdown?

Excessive mechanical force and wear over time

What is subchondral bone deterioration?

Breakdown or damage of the bone beneath articular cartilage

What are osteophytes?

Bone spurs that form at the margins of cartilage loss; hallmark of osteoarthritis

What happens to the synovial membrane in osteoarthritis?

It often becomes inflamed

What is lubricin?

A glycoprotein in synovial fluid that reduces friction in joints

What happens to lubricin in osteoarthritis?

Its concentration decreases, reducing joint lubrication

What is osteoporosis?

“Porous bone” characterized by low bone density and structural deterioration of bone tissue

What happens to bone structure in osteoporosis?

Breakdown of trabecular matrix leading to weakened, fragile bones

What is osteopenia?

Early stage of bone loss characterized by thinning of the trabecular matrix before osteoporosis develops

Why is osteoporosis called a “silent disease”?

It often has no symptoms until a fracture or height loss occurs

What are common signs of osteoporosis?

Pathological fractures and loss of height

What causes primary osteoporosis?

Prolonged negative calcium balance due to aging, poor diet, lack of exercise, low sex hormones, and low sunlight exposure

What causes secondary osteoporosis?

Underlying conditions affecting bone metabolism

• Hyperparathyroidism (Too much PTH, releases too much calcium from bones)

• corticosteroid use (Decreases osteoblast activity, increases osteoclast activity, decreases calcium absorption in intestines)

• malabsorption (Body cannot absorb vitamin D and calcium
  

What is the female athlete triad?

A condition involving

• amenorrhea (no period caused by low body fat and decreased energy, decreased levels of estrogen, Estrogen inhibits too much osteoclast activity)

• low body weight

• excessive exercise

leading to decreased bone density

What demographic factors increase risk for osteoporosis?

Female gender, postmenopausal status, Asian/Caucasian ethnicity, and family history

Why are postmenopausal women at higher risk for osteoporosis?

Decreased estrogen leads to increased bone resorption and decreased bone density

Why are males at risk for osteoporosis?

Low testosterone reduces bone maintenance and density

How does calcium and vitamin D intake affect osteoporosis risk?

Low intake reduces bone mineralization and increases bone loss

How does physical activity affect osteoporosis risk?

Lack of weight-bearing exercise increases bone loss

How do smoking, alcohol, and caffeine affect bone health?

They decrease bone density and impair bone formation

What medications increase osteoporosis risk?

Long-term corticosteroids (Decreases osteoblast activity, increases osteoclast activity, decreases calcium absorption in intestines)
Anticonvulsants (Increase breakdown of vitamin D in the liver)

How do thyroid and parathyroid disorders affect bone?

Hyperthyroidism: Speeds up metabolism, bone is broken down and rebuild faster than normal

Hyperparathyroidism: Too much PTH

What lifestyle or medical conditions increase osteoporosis risk?

• Eating disorders

• bariatric surgery

• excessive carbonated drinks (Too much phosphorus, decreases amount of free calcium, parathyroid produces more PTH)

• malnutrition

What is the most common diagnostic tests for osteoporosis?

• Dual-energy X-ray absorptiometry (DEXA) scan

• Quantitated CT

• Ultrasound densitometry

• X-rays

• Blood tests

• Urine

• FRAX risk assessmen
  

What does a DEXA scan measure?

Bone mineral density (BMD) using a T-score (compares BMD to healthy adult ~30)

What is quantitative CT used for in osteoporosis?

Measures trabecular bone density, especially in the spine

What does ultrasound densitometry measure?

Bone mass at peripheral sites such as the wrist or heel

What blood tests may be used in osteoporosis evaluation?

Calcium, thyroid hormones, PTH, estradiol, testosterone, and osteocalcin

What urine marker is used in osteoporosis?

Telopeptides (indicate bone resorption/breakdown)

What is the FRAX tool?

A risk assessment tool that estimates 10-year fracture risk for adults 40-90

What fractures does FRAX predict risk for?

Hip, spine, shoulder, and wrist fractures

What is osteoarthritis (OA)?

A degenerative joint disease characterized by progressive breakdown of cartilage and joint structures

A slowly progressive, degenerative, and inflammatory joint disease involving cartilage breakdown and joint surface changes

Which spine regions are commonly affected by OA?

Cervical spine and lumbosacral spine

Which lower extremity joints are commonly affected by OA?

Hip and knee joints

Which foot joint is commonly affected by OA?

First metatarsophalangeal (big toe) joint

Which joints are often spared in osteoarthritis?

Wrist, elbow, and ankle joints

What age group is most commonly affected by OA?

40+

How does OA develop over time?

Cumulative joint trauma and wear over a lifetime leads to cartilage degeneration and joint inflammation

What structural change is characteristic of OA?

Formation of osteophytes (bone spurs) along joint margins

Why does OA cause inflammation?

Cartilage breakdown leads to joint surface irritation and inflammatory response

How does excess body weight affect OA?

Increases stress on weight-bearing joints, accelerating cartilage wear

What are major risk factors for OA?

Aging, obesity, joint trauma/overuse, sports participation, heavy occupational work, and joint misalignment

What type of pain is typical in osteoarthritis (OA)?

Deep, aching joint pain that is often activity-related

Relieves with rest

How does weather affect OA symptoms?

Pain and stiffness often worsen in cold weather

What is morning stiffness like in OA?

Mild and short-lived, usually when first arising

What is crepitus in OA?

A grinding or crackling sound/feeling during joint movement

What mobility changes occur in OA?

Limited range of motion and altered gait

What joint changes are seen on physical exam in OA?

Swelling, tenderness, and possible joint deformity

What are Heberden’s nodes?

Bony enlargements at the distal interphalangeal (DIP) joints

What are Bouchard’s nodes?

Bony enlargements at the proximal interphalangeal (PIP) joints

What is the primary way OA is diagnosed?

Physical examination and X-rays
(Shows Joint space narrowing and osteophytes)

What serum markers may be seen in OA?

Osteocalcin and hyaluronic acid

What is degenerative disc disease (DDD)?

A condition where vertebral disc degeneration leads to nerve compression causing pain, motor weakness, and neuropathy

What body regions are most affected by DDD?

Cervical and lumbar spine

Which spinal nerve roots are most commonly affected in lumbar DDD?

L4, L5, and S1

How does DDD affect the nervous system?

Disc degeneration compresses spinal nerves, causing pain, weakness, and neuropathy

What is a herniated disc?

Displacement of disc material that compresses nearby spinal nerves

What is a bulging disc?

Disc protrusion that can press on spinal nerves without rupture

What is spinal stenosis?

Narrowing of the spinal canal, often due to osteophyte formation

What is spondylolisthesis?

Forward slippage of a vertebra over another vertebra

What is retrolisthesis?

Backward slippage of a vertebra

What causes nerve impingement in DDD?

Herniated discs, bulging discs, disc degeneration, osteophytes, and vertebral slippage

What is sciatica in degenerative disc disease (DDD)?

Low back pain that radiates down the back of the leg due to nerve root compression

What movements worsen pain in lumbar DDD?

Sitting, bending, lifting, and twisting

What relieves pain in lumbar DDD?

Walking, changing positions, or lying down

What are common neurological symptoms of lumbar DDD?

Numbness, tingling, weakness in legs, and possible foot drop (inability to lift front of foot)

What are symptoms of cervical DDD?

Neck pain radiating to shoulders and arms with numbness, tingling, and weakness in the upper extremities

Why are reflex, strength, and sensory tests important in DDD?

They help identify which spinal nerve root is affected

What imaging tests are used to diagnose DDD?

X-ray (Shows the bony and spacing changes)

MRI (Shows Disc degeneration, herniation, and nerve compression)

EMG (Evaluates nerve and muscle electrical activity to identify nerve dysfunction)

Is bone normally resistant to infection?

Yes, and infections happen, usually because of bacteria

How does bone infection (osteomyelitis) commonly occur?

Through a break in the bone or spread from the bloodstream

How do bacteria spread within bone tissue?

They invade the cortex through Haversian and Volkmann canals

(Channels in bone that allow blood vessels and nerves to pass through compact bone)

What conditions increase risk for bone infection?

• Immunosuppression

• diabetes mellitus (poor circulation which leads to low oxygen and low immune cell delivery which means that wounds are slower to heal and infections start easy and spread deep)

• nutritional deficiency (Impairs immune cell production, tissue repair, and collagen formation which means the body cannot fight or heal infections)

• prosthetic implants

Why is cartilage slow to heal during infection?

Cartilage is avascular, meaning it has no direct blood supply for repair or immune response

What happens to synovial fluid in joint disease or infection?

Its volume may increase, leading to joint swelling

What is joint effusion?

Abnormal accumulation of fluid (edema) within a joint

Why are musculoskeletal infections difficult to treat with medication?

Limited blood supply to cartilage and joint spaces reduces drug delivery

What is one method used to treat joint infections due to poor blood supply?

Intra-articular injections

What is contiguous spread of musculoskeletal infection?

Infection that spreads directly from an open wound or puncture site

What organism commonly causes contiguous musculoskeletal infections?

Staphylococcus aureus

What is hematogenous spread in musculoskeletal infection?

Infection that spreads through the bloodstream