Pathophysiology & Risk Factors

Osteoarthritis is a degenerative, NON-inflammatory joint disease driven by progressive breakdown of articular cartilage from mechanical wear and tear — not an autoimmune process. It targets weight-bearing joints (knees, hips) and the DIP joints of the hands. Distinguishing it from rheumatoid arthritis is the highest-yield discriminator on the NCLEX.

Osteoarthritis vs Rheumatoid Arthritis

OsteoarthritisRheumatoid Arthritis

NatureDegenerative wear-and-tear, localizedSystemic autoimmune inflammation

Joint patternAsymmetric, weight-bearing/large jointsSymmetric, small joints

Hand jointsDIP (Heberden) + PIP (Bouchard) nodesMCP + PIP, warm/boggy swelling

Morning stiffness< 30 min, improves with use> 1 hour, worse in morning

Pain patternWorse with activity, better with restImproves with use

Labs (ESR/CRP/RF)NormalElevated

Systemic symptomsNoneFatigue, fever, weight loss

Osteoarthritis

Nature: Degenerative wear-and-tear, localized
Joint pattern: Asymmetric, weight-bearing/large joints
Hand joints: DIP (Heberden) + PIP (Bouchard) nodes
Morning stiffness: < 30 min, improves with use
Pain pattern: Worse with activity, better with rest
Labs (ESR/CRP/RF): Normal
Systemic symptoms: None

Rheumatoid Arthritis

Nature: Systemic autoimmune inflammation
Joint pattern: Symmetric, small joints
Hand joints: MCP + PIP, warm/boggy swelling
Morning stiffness: > 1 hour, worse in morning
Pain pattern: Improves with use
Labs (ESR/CRP/RF): Elevated
Systemic symptoms: Fatigue, fever, weight loss

Signs & Symptoms

EarlyProgresses →

Joint pain worse with activity Hallmark

improves with rest

Brief morning stiffness

< 30 min, resolves with movement

Crepitus

grating sensation with movement

Late / Severe

Heberden nodes Hallmark

bony enlargement at DIP joints

Bouchard nodes

bony enlargement at PIP joints

Hard bony joint enlargement

not boggy/warm like RA

Decline in weight-bearing function

e.g. reduced stair-climbing ability

Diagnostics & Labs

Normal ESR

elevation suggests RA, not OA

Normal CRP

Normal rheumatoid factor

OA lacks systemic inflammation

Joint space narrowing on X-ray

Osteophytes on X-ray

bone spurs

Treatments & Medications

Weight reduction Hallmark

single most impactful non-pharmacologic step for knee OA

Low-impact exercise

swimming, cycling, water aerobics

AcetaminophenPrototype

first-line for mild pain

Topical NSAID

e.g. topical diclofenac; intermediate step before oral NSAIDs in older adults

Oral NSAID

moderate symptoms; monitor GI bleeding + renal function

Intra-articular corticosteroid injection

acute flares only; repeated use accelerates cartilage destruction

Joint replacement

arthroplasty when conservative measures fail

Patient Teaching

Stay active, avoid prolonged rest

immobility causes muscle atrophy and worsens stiffness

Heat for chronic stiffness

warm compress before morning activity

Cold for acute swelling

ice during active flares, not heat

Cane in opposite hand

hold on side opposite the most painful knee

Home assistive devices

grab bars, raised toilet seat reduce joint stress

Joint protection and pacing

Report Nowescalate immediately

Acute joint infection

hot, red, swollen joint with fever — septic arthritis

Severe loss of joint function

objective functional decline signals failing plan / surgical evaluation

GI bleeding on NSAID therapy

black/tarry stools, abdominal pain

Clinical Pearl

Heberden = DIP = farther from the Hand; Bouchard = PIP = closer to the Body. Normal labs + crepitus + activity pain that eases with rest = OA, not RA.