Joint swelling

Joint swelling means a joint has become enlarged, usually because it is inflamed or has extra fluid (an effusion) inside it. Distinguishing the pattern helps point to the cause. A single swollen joint after an injury suggests a mechanical problem — a sprain, a torn cartilage or ligament, or bleeding into the joint. A single hot, red, very painful swollen joint that comes on quickly is important: it can be gout (from uric acid crystals, classically the big toe) or, crucially, a joint infection (septic arthritis) — a medical emergency that can destroy a joint if not treated fast. When several joints swell, especially symmetrically and with morning stiffness, it points to an inflammatory arthritis such as rheumatoid arthritis, or to the spondyloarthritis family (reactive arthritis, psoriatic arthritis), or other autoimmune conditions like lupus. Osteoarthritis causes firmer, bony swelling of the finger joints and knees, usually with less heat. Swelling of a whole finger or toe (dactylitis) points to psoriatic or reactive arthritis. So the number of joints, the speed of onset, and whether the joint is hot and red are the features that separate an urgent infection from gout, inflammatory arthritis or a mechanical cause.

• Injury — a sprain, torn cartilage or ligament, or bleeding into the joint.
• Gout — a sudden hot, red, very painful joint, classically the big toe (uric acid crystals).
• Septic arthritis (joint infection) — a single hot, swollen, very painful joint; a medical emergency.
• Rheumatoid arthritis — several swollen joints, often symmetric, with morning stiffness.
• Spondyloarthritis (reactive, psoriatic) — often asymmetric, sometimes a whole swollen finger or toe.
• Lupus and other autoimmune conditions.
• Osteoarthritis — firmer, bony swelling with less heat.

The pattern guides testing. For a single hot, swollen, very painful joint, urgent assessment is needed and the joint fluid is often sampled to check for infection or crystals — this cannot wait. For several swollen joints or a suspected inflammatory arthritis, blood tests help: ESR and CRP (inflammation), rheumatoid factor and anti-CCP (rheumatoid arthritis), uric acid (gout, best checked away from an acute attack), and HLA-B27, ANA or others depending on the picture. Imaging assesses joint damage. Mediora.AI can surface an inflammatory (ESR, CRP), gout (uric acid) or rheumatoid (rheumatoid factor, anti-CCP) pattern from your results that fits the type of arthritis, but a single hot, swollen joint needs urgent in-person assessment to exclude infection, and the diagnosis of joint swelling belongs with your doctor.