Non-inflammatory degenerative joint disease driven by progressive articular cartilage loss.
Also known as: OA, degenerative joint disease, DJD, osteoarthrosis
Overview
Chronic degenerative joint disease characterized by progressive loss of articular cartilage, subchondral bone remodeling, osteophyte formation, and mild synovitis. Most commonly affects weight-bearing joints (knee, hip), the hand DIP/PIP and first CMC joints, and the cervical and lumbar spine.
Epidemiology
Most prevalent form of arthritis worldwide. Prevalence rises sharply after age 50; women > men after menopause. Symptomatic knee OA affects ~10% of US adults over 60.
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Question 1MusculoskeletalMedium
A 68-year-old woman reports several months of right knee and bilateral hand pain that worsens with activity and improves with rest. Morning stiffness lasts about 10 minutes. Exam shows bony enlargement at the distal interphalangeal joints and crepitus of the right knee without warmth or effusion. Radiographs show asymmetric joint-space narrowing, marginal osteophytes, and subchondral sclerosis. Inflammatory markers are normal. Which of the following is the most appropriate first-line pharmacologic treatment?
AOral duloxetine
BTopical diclofenac
CGlucosamine sulfate
DOral prednisone
Reveal answer & full explanation
Correct answer: B — Topical diclofenac
AOral duloxetine
BTopical diclofenac✓
CGlucosamine sulfate
DOral prednisone
Why Topical diclofenac is correct
This presentation is osteoarthritis, a degenerative joint disease distinguished from inflammatory arthritis by activity-related pain, brief morning stiffness (under 30 minutes), bony rather than soft-tissue swelling, normal inflammatory markers, and the classic radiographic tetrad of asymmetric joint-space narrowing, osteophytes, subchondral sclerosis, and cysts
First-line pharmacotherapy per ACR/OARSI guidance is a topical NSAID such as diclofenac, favored for knee and hand OA because it provides analgesia with minimal systemic exposure
Oral NSAIDs and duloxetine are added when needed; intra-articular corticosteroids treat acute flares
Why the others are wrong
Oral duloxetine — conditionally recommended for knee osteoarthritis, but ACR places it after topical and oral NSAIDs rather than as initial therapy, and it has little role in hand OA
Glucosamine sulfate — ACR strongly recommends against glucosamine for hand, hip, and knee osteoarthritis because trials show no benefit over placebo
Oral prednisone — used for systemic inflammatory and autoimmune arthritis; systemic steroids are not indicated for osteoarthritis and carry unnecessary metabolic risk
Additional high-yield points
The key misconception these distractors target is escalating to a systemic or unproven agent before trying the topical NSAID that guidelines place first
Question 2MusculoskeletalMedium
A 6-year-old boy is brought to the emergency department after falling from monkey bars onto an outstretched hand. He holds the right elbow slightly flexed and refuses to move it. There is marked swelling about the distal humerus with no skin tenting or laceration. The radial pulse is palpable, the hand is warm and pink, and capillary refill is 2 seconds. He is unable to flex the interphalangeal joint of the thumb or the distal interphalangeal joint of the index finger, and sensation is intact throughout the hand. A lateral radiograph shows the distal humeral fragment displaced posteriorly with no cortical contact between the fragments. Which of the following is the most appropriate next step in management?
AClosed reduction with percutaneous pinning
BLong-arm splint and outpatient follow-up
COpen reduction with internal fixation
DClosed reduction and long-arm casting
ESurgical exploration of the median nerve
Reveal answer & full explanation
Correct answer: A — Closed reduction with percutaneous pinning
AClosed reduction with percutaneous pinning✓
BLong-arm splint and outpatient follow-up
COpen reduction with internal fixation
DClosed reduction and long-arm casting
ESurgical exploration of the median nerve
Why Closed reduction with percutaneous pinning is correct
A fall onto an outstretched hand in a child of this age, with swelling at the distal humerus and posterior displacement of the distal fragment, describes an extension-type supracondylar humerus fracture, the most common elbow fracture in children.
Loss of all cortical contact makes this a Gartland type III injury. Completely displaced fractures are unstable and cannot be held by a cast, so the standard of care is closed reduction under anesthesia with percutaneous Kirschner wire fixation, generally the same day or within 24 hours.
A poorly perfused or white hand, an open fracture, or signs of compartment syndrome are what make the operation emergent rather than urgent. None of those is present here.
Inability to flex the thumb interphalangeal joint and the index distal interphalangeal joint with sensation fully intact is an isolated anterior interosseous nerve palsy, the classic neurologic finding with this fracture. The anterior interosseous nerve is a motor branch of the median nerve with no cutaneous sensory distribution, the injury is a neurapraxia in the great majority of cases, and it recovers spontaneously over weeks to months.
That palsy does not change the operation: the fracture is reduced and pinned, and the nerve is observed.
Why the others are wrong
Long-arm splint and outpatient follow-up — a splint is applied in the emergency department for comfort while the child awaits the operating room, but discharging him in it makes splinting the definitive treatment, which belongs to a nondisplaced Gartland type I fracture. A completely displaced fracture sent home unreduced risks malunion into cubitus varus (the trap is treating every pediatric elbow fracture as a splint-and-refer problem).
Open reduction with internal fixation — reserved for fractures that cannot be reduced closed, open fractures, and limbs requiring vascular exploration. Going open first adds soft-tissue injury, stiffness, and scarring to an injury that almost always reduces closed (the trap is reaching for open fixation simply because the fracture is completely displaced).
Closed reduction and long-arm casting — the reduction is the easy part; holding it is not. Without pins a completely displaced fracture redisplaces in the cast, and the elbow flexion needed to hold it compromises an already swollen limb (the trap is stopping one step short of definitive fixation).
Surgical exploration of the median nerve — an isolated anterior interosseous palsy accompanying a displaced supracondylar fracture is a traction neurapraxia that is observed, not explored. Exploration is considered only for a deficit that appears after manipulation with entrapment suspected, or for failure to recover over months (the trap is treating any motor deficit as a surgical emergency).
Additional high-yield points
Document the radial pulse, capillary refill, and the median, radial, and ulnar nerves before and after any manipulation. Test the median nerve's anterior interosseous branch with the OK sign, the radial nerve with wrist and thumb extension, and the ulnar nerve with finger abduction.
A pulseless white hand demands emergent reduction and pinning first, with open exploration of the brachial artery only if perfusion is not restored by the reduction. A hand that remains pulseless but warm, pink, and well perfused afterward is observed in hospital with serial perfusion checks over 24 to 48 hours.
The feared complication is Volkmann ischemic contracture from a missed forearm compartment syndrome. Pain out of proportion and pain on passive finger extension are the warning signs.
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Imbalance between cartilage matrix synthesis and degradation, driven by matrix metalloproteinases and pro-inflammatory cytokines (IL-1, TNF). Cartilage softens, fibrillates, and erodes. The underlying subchondral bone responds with sclerosis, cyst formation, and marginal osteophytes. Low-grade synovial inflammation contributes to pain but is qualitatively different from autoimmune arthritis.
Clinical presentation
Symptoms
Insidious joint pain worse with activity and improved by rest
Brief morning stiffness (<30 minutes) and gel phenomenon after inactivity
Reduced range of motion, crepitus, functional limitation
Knee: medial joint-line pain, buckling, difficulty with stairs
Hip: groin pain referred to thigh or buttock, limp
Hand: pain and bony enlargement at DIP (Heberden) and PIP (Bouchard) nodes; first CMC squaring
Signs / physical exam
Bony enlargement, crepitus, tenderness at joint line
Cool joint without significant warmth or erythema
Restricted ROM, antalgic gait
Mild effusion possible but lacking the boggy synovitis of RA
Classic findings
Heberden nodes (DIP) and Bouchard nodes (PIP); squared first CMC joint; medial knee joint-line tenderness.
Avascular necrosis (hip) — Groin pain with restricted internal rotation; crescent sign on plain film; MRI sensitive
Bursitis / tendinopathy — Periarticular tenderness without true joint-line pain; preserved passive ROM
Diagnostic workup
Diagnostic criteria
ACR clinical criteria for knee OA: knee pain plus at least 3 of: age >50, stiffness <30 min, crepitus, bony tenderness, bony enlargement, no palpable warmth. Radiographic hallmarks (Kellgren-Lawrence): joint-space narrowing, subchondral sclerosis, subchondral cysts, marginal osteophytes.
Labs
Generally not required for diagnosis when classic clinical and radiographic features present
ESR, CRP, RF, anti-CCP, ANA only if inflammatory arthritis suspected (should be normal or negative in OA)
Arthrocentesis only when effusion present and inflammatory or septic process must be excluded — OA fluid is non-inflammatory (WBC <2000, clear/straw-colored)
Imaging
Weight-bearing plain radiographs of the affected joint — first-line
MRI reserved for atypical presentations, suspected meniscal or ligamentous injury, or possible avascular necrosis
Ultrasound can detect effusion and osteophytes but is not routinely needed
Joint deformity (varus knee, fixed flexion of hip)
Perioperative complications of arthroplasty: infection, DVT/PE, periprosthetic fracture
PANCE pearls
Morning stiffness <30 minutes and pain that worsens through the day with activity favor OA over RA.
First CMC squaring and Heberden/Bouchard nodes are pathognomonic for primary hand OA.
ACR conditionally recommends AGAINST glucosamine, chondroitin, hydroxychloroquine, methotrexate, TNF inhibitors, and stem cell injections for OA.
If a patient with presumed OA develops a hot, swollen joint, perform arthrocentesis — superimposed gout, pseudogout, or septic arthritis can occur.
References
ACR/AF 2019 — 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee (Kolasinski et al., Arthritis Care Res 2020)
OARSI 2019 — OARSI Guidelines for the Non-Surgical Management of Knee, Hip, and Polyarticular Osteoarthritis (Bannuru et al., Osteoarthritis Cartilage 2019)
AAOS 2021 — AAOS Clinical Practice Guideline: Management of Osteoarthritis of the Knee (Non-Arthroplasty), 3rd ed.
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