Osteoarthritis for American Board of Internal Medicine (ABIM) Exam

Overview of Osteoarthritis (OA)

Definition: A degenerative joint disease characterized by the breakdown of articular cartilage and changes to subchondral bone, leading to joint pain, stiffness, and loss of function.

Pathophysiology

Cartilage Breakdown: Mechanical and biological processes lead to the loss of cartilage, exposing subchondral bone.
Bone Remodeling: Formation of subchondral sclerosis and osteophytes as compensatory changes to cartilage loss.
Low-Grade Inflammation: Mild synovial inflammation may be present but is not the primary driver, differentiating OA from other arthritides like rheumatoid arthritis.

Risk Factors

Age: Most significant risk factor; OA prevalence increases with age.
Obesity: Strong association with knee and hip OA due to increased mechanical load and metabolic factors.
Gender: Higher prevalence in women, particularly after menopause.
Joint Overuse/Trauma: History of joint injury, repetitive stress, and high-impact activities predispose to OA.
Genetics and Family History: Hereditary factors contribute to the development of OA, especially hand OA.

Symptoms and Signs

Joint Pain: Achy pain that worsens with use and improves with rest; typically affects large, weight-bearing joints.
Morning Stiffness: Lasts <30 minutes and improves with activity, unlike inflammatory arthritis.
Crepitus and Joint Swelling: Grinding or cracking sound with joint movement; minimal swelling compared to other forms of arthritis.
Joint Deformities: Bony enlargements and reduced joint mobility in advanced cases; Heberden’s nodes (DIP) and Bouchard’s nodes (PIP).
Common Joints Affected: Knees, hips, hands (especially DIP and PIP joints), first carpometacarpal joint, and spine.

Diagnosis

Clinical Presentation: Diagnosis is based on the characteristic symptoms and physical exam findings.
Radiographic Evaluation:

X-ray: Reveals joint space narrowing, osteophyte formation, subchondral sclerosis, and subchondral cysts.

Laboratory Tests: Usually normal; ESR and CRP may be mildly elevated or normal; used to exclude other arthritis etiologies.

Management

Exercise and Physical Therapy: Emphasize low-impact aerobic exercise, muscle strengthening, and stretching.
Weight Management: Weight loss to reduce stress on weight-bearing joints.
Assistive Devices: Use of braces, orthotics, and mobility aids as needed.

Acetaminophen: First-line for mild to moderate pain.
NSAIDs: For more severe pain; oral or topical formulations.
Topical Agents: Capsaicin, topical NSAIDs for focal pain relief.
Intra-Articular Injections: Corticosteroids for acute flares; hyaluronic acid may be used in select cases.

Surgical Treatment: Total joint replacement for advanced, refractory OA with significant pain and functional limitation.

Essential Points

Gradual Disease Progression: Symptoms worsen over time, and early management can slow progression and improve quality of life.
Imaging and Diagnosis: X-rays are key for confirming OA, showing characteristic features like osteophytes and joint space narrowing.
Comprehensive Management Strategy: A multimodal approach, including lifestyle changes, pharmacotherapy, and physical therapy, is essential for optimal care.
Individualized Therapy: Tailor treatment based on patient symptoms, joint involvement, and response to conservative therapy before considering surgical options.