Meniscus tear
Patellar dislocation
Fracture or bone bruise
In these cases, swelling often appears within hours and may be accompanied by pain, stiffness, or a feeling of instability in the joint.
2. Bursitis
Bursae are small fluid-filled sacs that cushion the knee. If one becomes irritated due to pressure, trauma, or kneeling for long periods, it can result in prepatellar bursitis (also known as “housemaid’s knee”). This usually affects only one knee and causes visible swelling at the front of the knee.
3. Infection
A joint infection or septic arthritis is a serious condition that can cause rapid swelling, redness, warmth, and severe pain in just one knee. This usually comes with fever or chills and requires urgent medical treatment. Joint aspiration may be needed to drain infected fluid.
