Arthritis means inflammation or damage of a joint, and the word covers many different diseases. The pattern of joints involved, the stiffness and the speed of onset help tell them apart.
Osteoarthritis
Articular cartilage wears down, the bone underneath thickens and bony spurs form. It affects weight-bearing joints and the end finger joints, with pain that worsens with use and short morning stiffness.
Rheumatoid arthritis
The immune system attacks the synovial membrane, which thickens and erodes cartilage and bone. It typically affects the small joints of both hands and wrists, with morning stiffness lasting more than an hour.
Gout
Uric acid crystals deposit in the joint and trigger sudden, intense inflammation, classically at the base of the big toe. Attacks often follow alcohol, a large meal or diuretics.
Septic arthritis
Bacteria infect the joint, usually a single large joint like the knee, causing a hot, swollen, very painful joint and often fever. It can destroy cartilage within days and is an emergency.
| Type | Main problem | Typical pattern |
|---|---|---|
| Osteoarthritis | Cartilage wear | Knees, hips, end finger joints |
| Rheumatoid arthritis | Autoimmune synovial inflammation | Small hand joints on both sides |
| Gout | Urate crystals | Sudden, one joint, often big toe |
| Septic arthritis | Bacterial infection | One hot joint, fever |
At the bedside
Any single hot, swollen joint is treated as septic arthritis until joint fluid analysis rules it out. Ask about morning stiffness, symmetry and which joints are involved to narrow the cause.
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Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).