Osteoarthritis
A mechanical disease in which cartilage breakdown outpaces chondrocyte repair, leaving a failing joint that remodels bone and hurts most with the use that drives the wear.
In a nutshell
Osteoarthritis is cartilage breakdown outpacing chondrocyte repair, driven by mechanical load, age and prior joint damage. The exposed subchondral bone remodels (sclerosis, cysts and osteophytes) and pain follows use because the mechanism is mechanical, not autoimmune.
Classic presentation
A patient over 45 with gradual-onset knee or hip pain that worsens through the day and with activity, brief morning stiffness under 30 minutes, and bony swelling with crepitus on examination.
Key points
- Osteoarthritis is a failure of cartilage repair to keep up with mechanical damage, not a primarily inflammatory process.
- Radiographic hallmarks (joint space narrowing, subchondral sclerosis, subchondral cysts, osteophytes) are sequential consequences of one mechanical mechanism.
- Pain is use-related and joints are affected asymmetrically, unlike the symmetrical, inflammatory, prolonged-morning-stiffness pattern of rheumatoid arthritis.
- Diagnosis can be made clinically in a patient over 45 with typical activity-related pain and minimal morning stiffness: imaging is not always required.
- There is no disease-modifying drug; management targets load (weight loss, exercise) and symptoms (analgesia), with joint replacement for severe structural failure.
First-line investigation
Clinical diagnosis in a patient over 45 with activity-related pain and minimal morning stiffness; plain radiograph if the picture is atypical or surgery is being considered.
First-line management
Education, therapeutic exercise and weight loss advice, with topical NSAIDs for symptomatic relief.
Exam traps
- Osteoarthritis pain improves with rest and worsens with use: the opposite pattern to inflammatory arthritis, where movement eases stiffness.
- Morning stiffness lasting over 30 minutes points away from osteoarthritis and towards an inflammatory arthritis.
- A hot, red, acutely swollen joint is not simple osteoarthritis. Think septic arthritis or crystal arthropathy and investigate urgently.
- There is no curative or disease-modifying drug for osteoarthritis; NSAIDs and analgesia are symptomatic only.
Educational content pending clinical review. Not medical advice.