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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- OA pain worsens with use and improves with rest; morning stiffness is usually <30 minutes
- Common sites: knees, hips, cervical/lumbar spine, first CMC, DIPs, and PIPs
- X-ray: asymmetric joint-space narrowing, osteophytes, subchondral sclerosis, and cysts
- First-line treatment is exercise, weight loss if overweight, physical therapy, and topical NSAIDs for hand/knee OA
- Inflammatory markers and autoantibodies are not routine unless inflammatory disease is suspected
Overview
Osteoarthritis is a degenerative whole-joint disorder involving cartilage loss, subchondral remodeling, osteophytes, synovial inflammation, and periarticular weakness. Diagnosis is usually clinical; imaging is reserved for uncertainty, trauma, severe disease, or surgical planning.
Epidemiology
Prevalence rises with age. Risk factors include older age, obesity, prior joint injury, repetitive loading, female sex, malalignment, and muscle weakness. Knee OA is strongly linked to obesity; hand OA has a strong genetic component.
Clinical Features
Symptoms
Deep aching pain worse with activity and relieved by rest
Brief morning stiffness or gelling after inactivity, typically <30 minutes
Difficulty climbing stairs, rising from chair, gripping, or walking
Hip OA pain localizing to groin, anterior thigh, or buttock
Sudden inability to bear weight suggests fracture, septic arthritis, or osteonecrosis
Warmth, prolonged stiffness, fever, or marked swelling suggests inflammatory or infectious arthritis
Signs
Crepitus, bony enlargement, and reduced range of motion
Heberden nodes at DIPs and Bouchard nodes at PIPs
First CMC squaring and pain with pinch grip
Varus knee alignment and medial joint-line tenderness
Limited internal rotation as an early sign of hip OA
Large effusion or severe pain with passive ROM suggests septic arthritis
Investigations
First-line
Clinical diagnosisTypical pattern and examination are often sufficient
Plain radiographsAsymmetric joint-space narrowing, osteophytes, subchondral sclerosis, subchondral cysts
No routine autoimmune labsOrder only if features suggest inflammatory arthritis, infection, or crystal disease
Second-line
MRIUse when osteonecrosis, occult fracture, meniscal injury, tumor, or alternate diagnosis is suspected
ArthrocentesisIf acute effusion, warmth, fever, or diagnostic uncertainty
Image-guided hip injectionCan confirm hip joint pain source and provide short-term relief
Specialist
Orthopedic assessmentSevere pain and disability despite conservative therapy or consideration of joint replacement
1
Core therapy
- Exercise is strongly recommended: aerobic, strengthening, aquatic, or neuromuscular programs
- Weight loss is strongly recommended for overweight patients with knee or hip OA
- Physical therapy, self-management, cane use, bracing, and hand orthoses when appropriate
2
Analgesia
- Topical NSAIDs are preferred initial medication for knee and hand OA
- Oral NSAIDs if no CKD, GI bleed risk, anticoagulation, uncontrolled HTN, HF, or high CV risk
- Acetaminophen has limited efficacy but can be used when NSAIDs are contraindicated
- Duloxetine can help chronic OA pain
3
Procedures
- Intra-articular glucocorticoid injections can provide short-term knee/hip relief
- Hyaluronic acid is generally not routinely recommended by ACR
- Total joint arthroplasty for severe pain and functional limitation despite nonoperative management
Complications
- Functional decline: Reduced mobility, falls, and loss of independence
- Chronic pain: Sleep disturbance, depression, and central sensitization
- Joint deformity: Varus knee, contracture, and reduced ROM
- Medication toxicity: NSAID-related GI bleeding, kidney injury, hypertension, and HF exacerbation
USMLE Step 2 CK Exam Tips
- 1OA stiffness is brief and pain worsens with use; RA stiffness is prolonged and improves with activity
- 2Heberden nodes = DIP OA; Bouchard nodes = PIP OA
- 3X-ray OA findings: asymmetric joint-space narrowing, osteophytes, subchondral sclerosis, cysts
- 4First-line knee OA in an overweight patient is weight loss plus exercise
- 5Topical NSAIDs are preferred before oral NSAIDs in older adults
- 6Hip OA presents as groin pain with limited internal rotation
- 7A hot swollen joint in OA still needs arthrocentesis
practicetest your knowledge on osteoarthritisApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — musculoskeletal and beyond.
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