Does osteoarthritis cause knee swelling in older adults?

Does Osteoarthritis Cause Knee Swelling?

Yes, osteoarthritis definitively causes knee swelling in older adults—the American College of Rheumatology explicitly identifies swelling as a cardinal manifestation of knee OA, resulting from synovial inflammation and joint effusions that are common features of the disease process. 1

Pathophysiology of Swelling in Knee OA

Osteoarthritis is characterized by pathology involving the entire joint, including:

• Synovial inflammation that directly produces joint swelling 1
• Cartilage degradation and bone remodeling that trigger inflammatory responses 1
• Osteophyte formation contributing to joint enlargement 1
• Joint effusions that are particularly common at the knee 2

The swelling in knee OA represents active disease pathology, not simply mechanical wear-and-tear. 1

Clinical Presentation

When evaluating knee swelling in older adults with suspected OA:

• Mild-to-moderate effusions are common at the knee in OA patients 2
• Inflammation is typically absent or only modest, distinguishing OA from inflammatory arthritis 2
• Bony enlargement occurs alongside soft tissue swelling 2
• Coarse crepitus, reduced range of movement, and joint-line tenderness accompany the swelling 2

Critical Diagnostic Distinctions

Important caveat: While OA causes swelling, certain features require urgent evaluation for alternative diagnoses:

• Soft tissue swelling with erythema or warmth suggests inflammatory arthritis or infection rather than OA 3
• Morning stiffness lasting ≥60 minutes indicates inflammatory arthritis, not OA 3
• Always aspirate and analyze synovial fluid if effusion is present to rule out infection before attributing swelling to OA alone 4

Management Implications

The presence of knee effusion in OA has specific treatment implications:

• Intra-articular corticosteroid injection is specifically indicated for acute exacerbations with joint effusion 4
• Better outcomes are seen with corticosteroid injection in patients with effusion, though injection should not be reserved only for those with visible swelling 4
• Short-term benefit is significant (effect size 1.27 over 7 days) for corticosteroid injection in swollen knees 4

Epidemiologic Context

Understanding the prevalence helps frame clinical expectations:

• 50% of adults aged 65 and older have OA, increasing to 85% in those 75 and older 3
• Knee OA affects approximately 27% of people aged 63-70 years, rising to 44% in those 80 years and older 1
• Women are disproportionately affected, with prevalence increasing after age 40 1