Knee osteoarthritis — SCE Rheumatology MCQ

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ModerateOsteoarthritis and soft tissue rheumatologyKnee osteoarthritisSCE Rheumatology

A 67-year-old woman reports 9 months of gradually progressive right knee pain. It is worse when walking downstairs and toward the end of the day, and improves with rest. Morning stiffness lasts approximately 10 minutes. Examination shows a small cool effusion, crepitus, bony enlargement and restricted flexion, without erythema or marked joint-line tenderness. She has no fever and no other symptomatic joints. What is the most likely diagnosis?

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Correct answer: C — Knee osteoarthritis

The diagnosis is knee osteoarthritis. The discriminating features are age over 45, chronic activity-related pain that worsens later in the day, brief morning stiffness, crepitus and bony enlargement, with no hot joint or systemic illness. A small cool effusion can occur in osteoarthritis and does not by itself imply inflammatory arthritis. NICE advises that this typical presentation can be diagnosed clinically without routine imaging. Calcium pyrophosphate arthritis and gout more commonly cause an acute, markedly inflammatory attack, although either can coexist with osteoarthritis. Septic arthritis usually presents with a painful hot joint and often systemic features, requiring urgent aspiration. Rheumatoid arthritis is characterised by persistent synovitis, prolonged morning stiffness and usually a polyarticular small-joint distribution rather than isolated bony knee disease.

Reference: National Institute for Health and Care Excellence. NG226, Osteoarthritis in over 16s: diagnosis and management, section 1.1 Diagnosis. 2022. https://www.nice.org.uk/guidance/ng226/chapter/recommendations