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Comprehensive Notes: Musculoskeletal Disorders (MSD) - Complete Module Guide

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MS-CM-001 | Low Back Pain (LBP)

Causes of Low Back Pain

A. Mechanical / Structural Causes (most common, ~85%)

B. Non-Mechanical Causes (Red Flags - Require Urgent Investigation)

• Neoplastic: primary or metastatic spinal tumors (pain worse at night/recumbent, not relieved by rest)
• Inflammatory: ankylosing spondylitis, reactive arthritis (morning stiffness >1 hour, improves with activity)
• Infectious: vertebral osteomyelitis, discitis, epidural abscess (fever, tenderness, history of IV drug use)
• Traumatic: vertebral fractures (post-trauma, or low-energy in osteoporotic patients)
• Vascular: aortic aneurysm (pulsatile mass, severe sudden onset, vascular risk factors)

C. Referred / Visceral Causes

• Kidney stones, pyelonephritis
• Pancreatic disease, retroperitoneal hematoma
• Gynecological causes (endometriosis, ovarian cysts)
• Prostate disorders

D. Psychosocial Factors (Yellow Flags)

• Depression, anxiety, catastrophization, fear-avoidance behavior
• Chronic LBP has co-prevalence of depression in 33-67%, anxiety in 10-30%
• Substance misuse disorders in 13-40%
• Biopsychosocial model: psychological and social factors significantly modulate pain perception

Red Flag Symptoms Warranting Imaging

• Progressive neurologic deficit (weakness, sensory loss, sphincter dysfunction)
• Pain aggravated by Valsalva/recumbency
• Post-trauma
• Fever + tenderness
• History of malignancy
• Night pain unrelieved by rest (Harrison's Principles of Internal Medicine 22E)

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Prevention of Low Back Pain

Primary Prevention

1. Exercise and core strengthening - Regular aerobic activity (walking, swimming); specific lumbar stabilization exercises strengthen paraspinal and abdominal muscles
2. Weight management - Obesity increases lumbar loading; BMI >30 is an independent risk factor
3. Ergonomic workplace design - Adjustable seating, lumbar support, avoiding prolonged static postures
4. Proper lifting technique - Squat-lift (spine neutral, power from legs); avoid twisting while lifting
5. Posture education - Neutral spine during sitting, standing, and sleeping; avoid prolonged forward flexion
6. Smoking cessation - Smoking impairs disc nutrition through reduced capillary flow

Secondary Prevention (Preventing Chronicity)

1. Early mobilization - Bed rest is NOT recommended; early return to normal activities improves outcomes
2. Physical therapy - Targeted physiotherapy, core stabilization, McKenzie exercises
3. Education and reassurance - Pain neuroscience education reduces fear-avoidance
4. Address psychosocial factors - Screen for depression/anxiety; cognitive behavioral therapy (CBT) has strong evidence for chronic LBP
5. Avoid over-medicalization - Avoid routine imaging for acute non-specific LBP (does not improve outcomes, increases nocebo effect)

Pharmacological Prevention of Progression

• NSAIDs as first-line for acute flares (not acetaminophen alone - no longer recommended as first-line)
• Muscle relaxants for acute spasm
• Duloxetine (SNRI) for chronic LBP with co-existing depression
• Opioids: last resort, short duration, lowest effective dose (Harrison's Principles of Internal Medicine 22E; Bradley and Daroff's Neurology)

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MS-CM-002 | Work-Related Musculoskeletal Disorders (WMSDs)

Definition

Burden / Epidemiology

• WMSDs comprise at least 50% of all nonfatal workplace injury cases resulting in days away from work
• The cost of work-related disability from MSDs in the United States was estimated at approximately 1% of gross national product
• Worldwide ergonomic/occupational disability from LBP in 2010 affected up to 26% of the global population
• Low back pain is the most common work-related musculoskeletal complaint globally
• Globally, approximately 1.71 billion people live with musculoskeletal conditions (Global Burden of Disease 2019)
• WMSDs are the leading contributor to disability worldwide
• Industries with highest rates: meatpacking, knit-underwear manufacturing, motor vehicle manufacturing, poultry processing, mail/message distribution, healthcare, construction, food processing, nursing assistance, agriculture
• Distribution of WMSDs by body region: neck (56%), shoulder (47%), lower back (46%) - from office worker studies 2024

Historical Occupation-Specific Syndromes (Table)

Risk Factors for WMSDs at the Workplace

Physical / Biomechanical Risk Factors

Organizational / Psychosocial Risk Factors

• Short work cycle times with little task variety
• Frequent tight deadlines, high cognitive demands
• Inadequate rest/recovery periods
• Little control over work pace or methods
• Cold work environment
• Localized mechanical stresses (e.g., pressing forearm against hard edge)
• Poor spinal support in seating

Prevention of Exposure to Workplace Risk Factors

Engineering Controls (Eliminate/Reduce the Hazard)

1. Workstation redesign - adjustable height desks, chairs with lumbar support
2. Mechanical assists - hoists, dollies, conveyor belts to reduce manual lifting loads
3. Anti-vibration tool handles and anti-fatigue mats
4. Tool/handle redesign to allow neutral wrist posture

Administrative Controls (Change Work Practices)

1. Job rotation - rotate workers between high-exposure and low-exposure tasks
2. Rest breaks - mandatory micro-breaks every 30-45 minutes for repetitive tasks
3. Pacing - avoid machine-paced work; allow worker control over speed
4. Limit cumulative lift weight per shift

Personal Protective Equipment and Training

1. Back support belts (limited evidence; do not replace engineering controls)
2. Training in proper lifting technique (squat-lift; load close to body; no twisting)
3. Ergonomics education programs
4. Early reporting of symptoms culture

Rehabilitation for Affected Workers

• Protection from aggravating tasks during recovery
• Restoration of strength and dynamic stability (physiotherapy)
• Graduated return-to-work programs with modified duties (Firestein & Kelley's Textbook of Rheumatology)

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MS-CM-003 | MSD Related to Mobile Usage

Burden / Epidemiology

• Prevalence of musculoskeletal complaints among mobile device users: 1.0% to 67.8% (wide range due to study design differences)
• Studies consistently show significant association between smartphone use time and neck/shoulder pain intensity
• Among students with text neck syndrome: 31.7% have mild neck disabilities, with higher prevalence in females (40%)
• Significant correlation between smartphone addiction scale scores and neck disability index (NDI)
• Repetitive thumb use on touchscreens is increasingly linked to de Quervain tenosynovitis and trigger thumb

Disorders Related to Mobile Usage

1. Text Neck Syndrome

• Definition: Overuse injury of the cervical spine caused by sustained forward-flexed head posture while looking at a mobile device
• Mechanism: For every inch the head moves forward, the effective weight on the cervical spine increases. At 0° (neutral), head weighs ~12 lbs; at 60° flexion (typical texting posture), effective load is ~60 lbs
• Symptoms: Neck pain, stiffness, headaches, radiating pain to shoulders/arms, reduced cervical range of motion, early degenerative changes
• Structures affected: Cervical muscles (trapezius, levator scapulae, sternocleidomastoid), cervical discs, facet joints, ligaments
• Epidemiology: Prevalence rising particularly among youth; females more affected; correlates directly with daily screen time

2. Trigger Thumb (Stenosing Flexor Tenosynovitis)

• Definition: Inflammation of the flexor pollicis longus tendon sheath causing a size mismatch between the tendon and its sheath at the A1 pulley
• Mechanism: Repetitive thumb flexion (typing, scrolling, gaming) causes microtrauma and inflammation at the first annular (A1) pulley
• Symptoms: Pain and clicking/locking of the thumb in flexion; may progress to fixed flexion deformity
• In adults: Associated with repetitive smartphone use; middle-aged women particularly affected
• Treatment: Rest, splinting, corticosteroid injection; surgical A1 pulley release for refractory cases (Campbell's Operative Orthopaedics 15th Ed; Sabiston Textbook of Surgery)

3. De Quervain Tenosynovitis

• Definition: Stenosing tenosynovitis of the first extensor compartment of the wrist (abductor pollicis longus + extensor pollicis brevis tendons)
• Mechanism: Repetitive pinching, gripping, and lateral deviation of the wrist - common with texting, scrolling, gaming
• Typical patient: Middle-aged women, new mothers, golfers, and increasingly smartphone users
• Symptoms: Pain and swelling at the radial styloid/base of thumb; positive Finkelstein test (thumb in palm, ulnar deviation = pain)
• Treatment: Thumb spica splint, NSAIDs, corticosteroid injection into first extensor compartment; surgical release of first compartment if conservative treatment fails (Miller's Review of Orthopaedics; Sabiston Textbook of Surgery)

4. Carpal Tunnel Syndrome (CTS)

• Definition: Compression of the median nerve within the carpal tunnel at the wrist
• Mechanism: Prolonged wrist flexion/extension while holding devices; sustained grip; repetitive tapping on screens increases pressure in carpal tunnel
• Risk factors: Female sex, age 40-60, repetitive wrist use, vibration, obesity, diabetes, hypothyroidism, pregnancy
• Symptoms: Numbness/tingling in the thumb, index, middle, and radial half of ring finger (median nerve distribution); nocturnal symptoms; thenar wasting in severe cases
• Tests: Tinel's sign (tapping over carpal tunnel), Phalen's test (sustained wrist flexion x 60 sec)
• Treatment: Wrist splint in neutral position (especially nocturnal), corticosteroid injection, surgical carpal tunnel release (Sabiston Textbook of Surgery; Goldman-Cecil Medicine)

Risk Factors for Mobile-Related MSD

1. Duration of use - >2-3 hours/day continuous use is high-risk
2. Posture - Neck forward flexion >30°, wrist flexion/deviation during typing
3. Grip force - Tight grip on device activates forearm flexors excessively
4. Lack of breaks - No rest between sessions
5. Device size - Smaller screens require more neck flexion and finer thumb movements
6. Age - Young adults (students) are highest-risk group by exposure time
7. Sex - Females have higher prevalence (smaller tendon sheaths, hormonal factors)
8. Existing conditions - Diabetes, hypothyroidism, obesity amplify CTS risk
9. Phone addiction/behavioral factors - Nomophobia, compulsive checking behavior

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MS-CM-004 | Ergonomics Applied to MSD Prevention

Definition of Ergonomics

Domains of Ergonomics

Application to Specific Disorders

For Low Back Pain (Office/Industrial Ergonomics)

• Chair height: Feet flat on floor, hips and knees at 90°, lumbar lordosis supported
• Monitor height: Top of screen at or slightly below eye level (prevents neck flexion)
• Desk height: Elbows at 90° when typing; forearms parallel to floor
• Sit-stand workstations: Alternate sitting and standing every 30-60 minutes
• Monitor distance: Arm's length (~50-70 cm) from eyes
• Consequences of poor ergonomics: Repetitive microtrauma, sustained muscle activation, cumulative loading on discs and joints leading to pain and injury

For Text Neck / Mobile Use

• Device position: Hold phone at eye level rather than neck-flexed position
• Neutral cervical posture education: Ear directly over shoulder over hip in sagittal plane
• Screen angle apps/stands: Use phone stands/holders rather than holding device
• Take micro-breaks: 20-20-20 rule modified for neck: every 20 minutes, look up for 20 seconds
• Voice input: Use voice-to-text to reduce thumb and neck loading

For De Quervain / Trigger Thumb

• Pinch vs. whole-hand grip: Use larger buttons/keys; avoid repetitive pinch grip
• Ergonomic phone cases: Finger rings/loops reduce need for tight gripping
• Stylus use: Reduces direct screen-tapping forces
• Break frequency: Thumb stretching every 30 minutes

For Carpal Tunnel Syndrome

• Wrist posture: Maintain neutral wrist (0° flexion/extension) during typing
• Ergonomic keyboards: Split keyboards, negative tilt keyboards reduce wrist deviation
• Wrist rests: Used correctly (between keystrokes, not while typing) reduce sustained loading
• Mouse ergonomics: Vertical mice maintain forearm in neutral pronation/supination
• Voice recognition software: Reduces total keying volume

Ergonomics in Surgical / Clinical Settings

• Surgeons' MSD burden: 68% of surgeons report generalized pain from operating; back (50%), neck (48%), arm/shoulder (43%)
• Healthcare sector: In 2022, had the highest number of nonfatal work-related injuries (665,300 in the US)
• Anti-fatigue mats: Reduce cumulative loading on lower limbs during prolonged standing
• Adjustable OR table height: Maintain surgeon's elbows at ~90° for open procedures
• Laparoscopic ergonomics: Monitor at eye level; instrument handles fit surgeon's grip span (Sabiston Textbook of Surgery)

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MS-CM-005 | Non-Communicable Musculoskeletal Disorders (NCDs)

Concept

Key Characteristics

• Chronic course: Persistent or recurrent symptoms lasting months to years
• Multifactorial etiology: No single cause; risk factors are cumulative
• Major disability burden: MSDs are the highest contributor to the global rehabilitation need
• Prevention-oriented: Most risk factors are modifiable

Major Non-Communicable MSDs

Common Risk Factor Framework for Non-Communicable MSDs

• Non-modifiable: Age, sex, genetics, race/ethnicity
• Modifiable lifestyle: Physical inactivity, obesity, smoking, poor nutrition, excessive alcohol
• Biomechanical: Repetitive loading, poor posture, occupational exposure
• Metabolic: Diabetes, vitamin D deficiency, calcium deficiency

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MS-CM-006 | Risk Factors for Osteoporosis in the Community

Risk Factors

Non-Modifiable Risk Factors

Modifiable Lifestyle Risk Factors

Medical / Pharmacological Risk Factors

Community-Level Prevention of Osteoporosis

• Physical activity: Weight-bearing and resistance exercise (walking, jogging, resistance training) at all ages; particularly in adolescence to maximize peak bone mass
• Calcium intake: 1200-1500 mg/day for adults over 50 (dairy, leafy greens, fortified foods)
• Vitamin D supplementation: 800-1000 IU/day for adults over 50; sun exposure (15-30 min/day)
• Fall prevention programs: In the elderly (home hazard removal, balance training, vision correction)
• Smoking cessation and alcohol reduction
• Screening: DXA scan for women >65 years and postmenopausal women <65 with risk factors (FRAX score)
• Pharmacological: Bisphosphonates (alendronate, zoledronic acid) for confirmed osteoporosis or fragility fracture - inhibit osteoclastic bone resorption

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Quick Reference Summary

• WHO Musculoskeletal Fact Sheet - 1.71 billion people globally affected
• Harrison's Principles of Internal Medicine 22E
• Firestein & Kelley's Textbook of Rheumatology
• Miller's Review of Orthopaedics 9th Edition
• Sabiston Textbook of Surgery (Ergonomics chapter)
• Campbell's Operative Orthopaedics 15th Ed 2026