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Approach to Articular and Musculoskeletal Disorders¶

Chapter 382 | Part 11: Immune-Mediated, Inflammatory, and Rheumatologic Disorders · Part 11 – Rheumatology & Immunology · Chapter 382

Key Clinical Points¶

Distinguish articular (synovium, joint capsule, cartilage) from nonarticular (tendons, bursae, muscle) origins of pain.
Identify 'Red Flag' conditions requiring urgent evaluation: septic arthritis, acute crystal-induced arthritis (gout), fracture, vascular ischemia, and Camper's syndrome.
Inflammatory disorders are characterized by prolonged morning stiffness (>45 min), systemic symptoms (fever, weight loss), and elevated inflammatory markers (ESR/CRP).
Noninflammatory disorders typically present with pain on active motion only, no swelling, and a brief 'gel phenomenon' (≤ 45 min).
Fibromyalgia is a common masquerader characterized by pain amplification, sleep disturbance, and tender trigger points without objective inflammatory signs.
Drug-induced musculoskeletal conditions are common; thorough review of medication history is essential for myopathy, arthritis, or osteonecrosis.
Elderly patients are at high risk for OA, pseudogout, rotator cuff disorders, and have lower reliability in laboratory markers (e.g., ESR/RF).
Hand pain patterns differ significantly: OA affects DIP/PIP/1st CMC; RA affects PIP/MCP/wrist; Psoriatic arthritis involves dactylitis.
Shoulder pain may originate from the glenohumeral joint, acromioclavicular joint, subacromial bursa, rotator cuff, or be referred from the cervical spine.
Acute monoarticular inflammatory arthritis requires arthrocentesis to rule out infection before initiating immunosuppression.

DEFINITION & OVERVIEW¶

• Articular vs. Nonarticular Structures: → Articular: Synovium, synovial fluid, articular cartilage, intraarticular ligaments, joint capsule, and juxtaarticular bone. → Nonarticular (Periarticular): Supportive extraarticular ligaments, tendons, bursae, muscle, fascia, bone, nerve, and overlying skin.

• Articular Disorders: → Characterized by deep or diffuse pain; limited range of motion (ROM) on both active and passive movement; swelling (synovial proliferation, effusion, or bony enlargement); crepitation; instability; locking; or deformity.

• Nonarticular Disorders: → Painful on active, but not passive (or assisted) ROM; point or focal tenderness in regions adjacent to articular structures; may radiate or be elicited with specific movements/positions; physical findings remote from the joint capsule; seldom demonstrate swelling, crepitus, instability, or deformity.

• Goals of Evaluation: 1. Accurate diagnosis (Determine chronology: acute vs chronic) 2. Timely provision of therapy (Determine nature: inflammatory vs noninflammatory) 3. Avoidance of unnecessary testing (Anatomic localization: articular vs nonarticular) 4. Identification of 'red flag' conditions (Extent of involvement: mono, poly, focal, or widespread)

• Red Flag Conditions: → Suspected by acute onset of monoarticular or focal musculoskeletal pain. → Includes: Septic arthritis, acute crystal-induced arthritis (e.g., gout), fracture, vascular ischemia, and Camper's syndrome.

EPIDEMIOLOGY¶

• General Prevalence: → Affects 1 in 3 (approx. 127 million) in the U.S.; accounts for 15–25% of all outpatient visits. → 54.4 million (22.7%) of U.S. adults have physician-diagnosed arthritis.

• Age Distribution: → Under 60 years: Trauma/fracture, low back pain, repetitive strain injury (tendinitis, bursitis), gout (males only), RA, spondyloarthritis. → Over 60 years: OA, crystal (gout and pseudogout) arthritis, PMR, osteoporotic fracture, uncommonly septic arthritis. → Middle age: Fibromyalgia and RA are frequent. → Elderly: OA and PMR are more prevalent. → Young adults: SLE and gonococcal arthritis occur more frequently.

• Sex and Race: → Male predominance: Gout, spondyloarthritis, and ankylosing spondylitis. → Female predominance: RA, lupus, fibromyalgia, osteoarthritis, and osteoporosis. → Racial predilections: → PMR, giant cell arteritis, and GPA commonly affect whites. → Sarcoidosis and SLE more commonly affect African Americans.

ETIOLOGY & PATHOPHYSIOLOGY¶

• Inflammatory vs. Noninflammatory: → Inflammatory: Suggested by 4 cardinal signs (erythema, warmth, pain, swelling), systemic symptoms (fever, rash, weight loss), or lab evidence (elevated ESR/CRP, thrombocytosis, anemia of chronic disease, hypoalbuminemia). → Noninflammatory: Characterized by lack of inflammatory markers and absence of systemic features.

• Stiffness Differentiation: → Inflammatory: Prolonged duration (hours) with conditions like RA or PMR; improves with activity. → Noninflammatory: Short-lived/intermittent "gel phenomenon" (≤ 45 min); exacerbated by activity (e.g., OA).

• Fatigue: → Present in inflammatory states (RA, PMR) and noninflammatory conditions (fibromyalgia, chronic pain, anemia, cardiac failure, etc.).

• Noninflammatory Etiologies: → Trauma (rotator cuff tear) → Repetitive use (bursitis, tendinitis) → Degeneration/ineffective repair (OA) → Neoplasm (pigmented villonodular synovitis) → Pain amplification (fibromyalgia).

• Drug-Induced Conditions: → Includes enthesitis, dermatomyositis, lupus, subacute lupus, vasculitis, osteonecrosis, osteopenia, psoriasis, systemic sclerosis, Raynaud's phenomenon.

CLINICAL FEATURES¶

• Chronicity and Onset: → Acute (≤ 6 weeks): Infectious, crystal-induced, or reactive. → Chronic (> 6 weeks): Noninflammatory (OA) or immune-mediated (RA, polymyositis). → Abrupt onset: Septic arthritis or gout. → Indolent onset: OA, RA, and fibromyalgia. → Evolution patterns: → Chronic: OA → Additive: RA, psoriatic arthritis → Intermittent: Crystal or Lyme arthritis → Migratory: Rheumatic fever, gonococcal or viral arthritis.

• Distribution of Involvement: → Monoarticular (1 joint): Crystal and infectious arthritis. → Oligo/Pauciarticular (2–3 joints): Spondyloarthritis, reactive arthritis, gout. → Polyarticular (>5 joints): OA and RA. → Upper extremities: Frequently involved in RA and OA. → Lower extremity: Characteristic of reactive arthritis and gout at onset. → Spine: Common in OA and axial spondyloarthritis; infrequent in RA (except cervical).

• Regional Complaints: → Hand Pain: → Focal/Unilateral: Trauma, overuse, infection, or reactive/crystal-induced. → Bilateral: Degenerative (OA), systemic, or inflammatory/immune (RA). → OA: DIP and PIP with bony hypertrophy (Heberden's/Bouchard's nodes); 1st CMC joint. → RA: Additive, symmetric; PIP, MCP, intercarpal, and carpometacarpal joints (wrist). → Psoriatic arthritis: Mimics OA (DIP/PIP) but with dactylitis (sausage-like swelling). → Tenosynovitis: Swelling/pitting edema; pain during extension stretch. → Carpal Tunnel: Wrist pain radiating to thumb, 2nd, 3rd, and radial half of 4th finger. → Shoulder Pain: → Origins: Glenohumeral or acromioclavicular joints, subacromial (subdeltoid) bursa, periarticular soft tissues. → Referred pain: Cervical spine, intrathoracic lesions (Pancoast tumor), gallbladder, liver, or diaphragm. → Rotator Cuff: Pain on active abduction (not passive), night pain, impingement signs (Neer test, drop arm test).

• Systemic and Extraarticular Manifestations: → Fever: Still's disease, infection. → Rash: SLE, psoriatic arthritis. → Nail abnormalities: Psoriatic or reactive arthritis. → Myalgias: Fibromyalgia, statin- or drug-induced myopathy. → Weakness: Polymyositis, neuropathy. → Eyes: Behçet's disease, sarcoidosis, spondyloarthritis. → GI tract: Systemic sclerosis, IBD. → Genitourinary: Reactive arthritis, gonococci. → Nervous system: Lyme disease, vasculitis.

DIFFERENTIAL DIAGNOSIS¶

• Core Diagnostic Questions: 1. Articular or nonarticular? 2. Inflammatory or noninflammatory? 3. Acute or chronic? 4. Localized (monoarticular) or widespread (polyarticular)?

• Acute Inflammatory Monoarthritis: → Septic arthritis, Gout, Pseudogout, Reactive arthritis, Initial presentation of chronic arthritis.

• Chronic Inflammatory Polyarthritis: → Rheumatoid arthritis, SLE, Scleroderma, Polymyositis.

• Chronic Noninflammatory: → Osteoarthritis, Fibromyalgia, Polymyalgia rheumatica.

• Drug-Induced: → Drug-induced arthritis, myopathy, lupus, osteonecrosis.

DIAGNOSTIC APPROACH¶

Initial Screening: Identify 'Red Flag' conditions (Septic arthritis, Gout, Fracture, Vascular ischemia, Camper's syndrome) to determine need for immediate intervention.
Anatomical Localization: Determine if the complaint is articular or nonarticular based on:
Presence of swelling/crepitus/instability (Articular).
Pain only on active motion; no swelling (Nonarticular).
Inflammatory Assessment: Evaluate for inflammatory markers and clinical signs:
Duration of morning stiffness (>45 min = Inflammatory; ≤ 45 min = Noninflammatory).
Systemic symptoms (fever, weight loss) and lab values (ESR/CRP elevation).
Distribution Analysis:
Monoarticular: Suggests crystal or infectious.
Oligoarticular (≤ 2 joints): Suggests spondyloarthritis or reactive.
Polyarticular (>5 joints): Suggests RA or OA.
Synovial Fluid Analysis (if monoarticular inflammatory is suspected):
Step 1: Is effusion hemorrhagic?
Yes → Consider: Trauma/mechanical derangement, Coagulopathy, Neuropathic arthropathy.
No → Proceed to Step 2.
Step 2: Is WBC > 2000/μl?
No → Noninflammatory articular conditions (Osteoarthritis, Trauma, Other).
Yes → Consider inflammatory or septic arthritis → Proceed to Step 3.
Step 3: Is PMN % > 75%?
Yes → Are crystals present?
Yes → Crystal identification (Gout, Pseudogout).
No → Proceed to Step 4.
No → Proceed to Step 4.
Step 4: Is WBC > 50,000/μl?
Yes → Possible septic arthritis.
No → Possible inflammatory arthritis.
Systemic Markers (ANA Patterns):
Diffuse: Non-specific; Histones (Drug-induced lupus, lupus).
Speckled: U1-RNP (>90% MCTD); Sm (30% SLE); Ro (Sjögren's, SCLE); La (Sjögren's);
Scl-70: 40% of diffuse cutaneous systemic sclerosis.
Centromere: 75% CREST (limited cutaneous systemic sclerosis), PBC.

MANAGEMENT & TREATMENT¶

Initial Management:
Rule out infection (arthrocentesis required for acute monoarticular inflammation before starting immunosuppression).
Identify and address 'Red Flag' conditions immediately.
Drug-Induced Management:
Review medication history for drugs causing myopathy, arthritis, or osteonecrosis.
Discontinue offending agents if possible.
Regional Management:
Hand: Splinting, NSAIDs, DMARDs (for inflammatory).
Shoulder: Physical therapy, corticosteroid injections, surgical repair (rotator cuff).
Fibromyalgia: Sleep hygiene, exercise, antidepressants.
Monitoring:
Monitor for disease progression in chronic conditions.
Monitor for drug toxicity and complications (infection, cardiovascular events, pulmonary disorders, neoplasia).

COMPLICATIONS & PROGNOSIS¶

• Acute Monoarticular: May require hospitalization if infection is suspected.

• Chronic Inflammatory Disorders (RA, SLE, Psoriatic): → Increased risk of: Infection, cardiovascular events, pulmonary disorders, and neoplasia.

• Fibromyalgia: Chronic pain amplification disorder; no structural progression but impacts quality of life.

• Drug-Induced Conditions: May resolve upon discontinuation of the offending agent.

SPECIAL CONSIDERATIONS¶

• The Elderly Patient: → High prevalence of joint complaints (58% of those >65). → Common conditions: OA, osteoporosis, fractures, gout, pseudogout, rotator-cuff disorders, PMR, vasculitis, septic arthritis. → Lab Reliability: ESR may be misleadingly elevated; low-titer RF and ANA seen in up to 15% of elderly patients.

• The Hospitalized Patient: → Challenges: Symptom severity, acute/chronic overlap, comorbidities. → Reasons for admission: 1. Acute inflammatory arthritis (Gout or Septic). 2. Undiagnosed systemic/febrile illness. 3. Musculoskeletal trauma. 4. Exacerbation of existing disorder. 5. New medical diagnoses (thrombotic, lymphoma, infection).

• Fibromyalgia: → Characterized by: Sleep disturbance, exaggerated pain/sensitivity, and multiple symptoms (IBS, migraine, fatigue). → Clinical findings: Paucity of abnormalities on exam; presence of tender 'trigger points' (epicondyles, trochanteric bursae, anserine bursae).

KEY PEARLS & CLINICAL TRAPS¶

• Red Flags: Septic arthritis, acute crystal-induced arthritis (gout), fracture, vascular ischemia, and Camper's syndrome.

• Fibromyalgia: A common masquerader; early consideration can avert needless investigation.

• Nonarticular Rule: These conditions seldom show swelling, crepitus, instability, or deformity.

• Inflammatory Markers: Use of ESR/CRP to distinguish inflammatory from noninflammatory processes.

• Synovial Fluid Thresholds: - WBC > 2000/μl → Inflammatory/Septic. - PMN > 75% → Suggests infection or crystal disease. - WBC > 50,000/μl → High suspicion for septic arthritis.

Reference Tables¶

TABLE 382-1 Evaluation of Patients with Musculoskeletal Complaints Goals¶

Harrison's 22e, p.2938

Goals
Accurate diagnosis
Timely provision of therapy
Avoidance of unnecessary diagnostic testing
Identification of “red flag” conditions
Approach
Determine the chronology (acute vs chronic)
D etermine the nature of the pathologic process (inflammatory vs
noninflammatory)
Anatomic localization of complaint (articular vs nonarticular)
D etermine the extent of involvement (monoarticular, polyarticular, focal,
widespread)
Consider the most common disorders first
Consider the need for diagnostic testing
Formulate a differential diagnosis

TABLE 382-3 Glossary of Musculoskeletal Terms Crepitus¶

Harrison's 22e, p.2942

Crepitus
A palpable (less commonly audible) vibratory or crackling sensation elicited
with joint motion; fine joint crepitus is common and often insignificant in
large joints; coarse joint crepitus indicates advanced cartilaginous and
degenerative changes (as in osteoarthritis)
Subluxation
Alteration of joint alignment such that articulating surfaces incompletely
approximate each other
Dislocation
Abnormal displacement of articulating surfaces such that the surfaces are not
in contact
Range of motion
For diarthrodial joints, the arc of measurable movement through which the
joint moves in a single plane
Contracture
Loss of full movement resulting from a fixed resistance caused either by
tonic spasm of muscle (reversible) or by fibrosis of periarticular structures
(permanent)
Deformity
Abnormal shape, size, or alignment resulting from bony hypertrophy,
malalignment of articulating structures, or damage to periarticular supportive
structures
Enthesitis
Inflammation of the entheses (tendinous or ligamentous insertions on bone)
Epicondylitis
Infection or inflammation involving an epicondyle

TABLE 382-4 Antinuclear Antibody (ANA) Patterns and Clinical Associations¶

Harrison's 22e, p.2946

ANA PATTERN	ANTIGEN IDENTIFIED	CLINICAL CORRELATE
Diffuse	Deoxyribonucleoprotein	Nonspecific
	Histones	Drug-induced lupus, lupus
	ds-DNA
Speckled	U1-RNP	>90% of MCTD
	Sm	30% of SLE (specific)
	Ro (SS-A)	Sjögren’s 60%, SCLE, neonatal lupus, ANA (–) lupus
	La (SS-B)	50% of Sjögren’s, 15% lupus
	Scl-70 (topoisomerase I)	40% of diffuse cutaneous systemic sclerosis
	Jo-1 (histidyl t-RNA synthetase)	PM with pneumonitis + arthritis
	RNA polymerase I, others
Centromere	Kinetochore	75% CREST (limited cutaneous systemic sclerosis), PBC, Sjögren’s, thyroiditis
Strongly consider synovial fluid aspiration and analysis if there is • Monarthritis (acute or chronic) • Trauma with joint effusion • Monarthritis in a patient with chronic polyarthritis • Suspicion of joint infection, crystal-induced arthritis, or hemarthrosis

TABLE 382-5 Diagnostic Imaging Techniques for Musculoskeletal Disorders METHOD Ultrasound¶

Harrison's 22e, p.2947

METHOD	COSTa	CURRENT INDICATIONS	CAVEATS
Ultrasound	++	Synovial (Baker’s) cysts Rotator cuff tears Bursitis, tendinitis, tendon injury Enthesitis Carpal tunnel syndrome Urate or calcium pyrophosphate deposition on cartilage Early detection of synovial inflammation or erosions Ultrasound-guided injection/ arthrocentesis	Operator dependent
	++	Metastatic bone survey Evaluation of Paget’s disease Identifying occult arthritis in patients with undiagnosed polyarthralgia Acute infection Prosthetic infection Acute osteomyelitis Acute and chronic infection Acute osteomyelitis
	++	Arthritis Inflammation Degeneration Metastases Infection
	+++	Septic arthritis
	++++	Prosthetic joint infection
Computed tomography (CT)	++++	Herniated intervertebral disk Sacroiliitis Spinal stenosis Spinal trauma Osteoid osteoma Stress fracture	Ionizing radiation exposure Contrast use Availability of CT angiography
	+++	Uric acid deposition Tophus localization
Magnetic resonance imaging	++++	Avascular necrosis Osteomyelitis Septic arthritis, infected prosthetic joints Sacroiliitis Intraarticular derangement and soft tissue injury Derangements of axial skeleton and spinal cord Herniated intervertebral disk Pigmented villonodular synovitis Inflammatory and metabolic muscle pathology	Cost Contrast use No ionizing radiation Soft tissue detail
	+++++++