The most common causes of knee joint pain are osteoarthritis in people over 45, and injuries such as meniscus tears, ligament sprains and kneecap pain in younger, active people. Where it hurts, how it started and what makes it worse point to the cause. A doctor confirms it with an exam and sometimes imaging.
Causes by how it started
| How it started | Likely causes |
|---|---|
| Slowly over months or years | Arthritis, runner's knee |
| Twist or pivot, then swelling | Meniscus tear, ligament injury |
| Suddenly, red and hot, no injury | Gout, infection |
| Swelling over or behind the kneecap | Bursitis, Baker's cyst |