If Your Knee Is Swollen: What to Do

Knee swelling may come from fluid inside the joint, inflammation around it, bleeding after an injury, or irritation of nearby tissues. A twist with a pop and rapid swelling can occur with an ACL tear or another internal injury. Gradual swelling may accompany knee osteoarthritis, while tenderness over the kneecap can fit knee bursitis. A swollen knee can also be a presentation of gout or infection, so swelling alone cannot identify the cause.

A clinician may assess the injury, movement, warmth, redness, stability, and fluid pattern. The cause may be an ACL tear, Baker's cyst, gout, knee bursitis, knee osteoarthritis, or meniscus tear, among other possibilities.

Pause running, jumping, kneeling, and heavy lifting. Rest the leg in a comfortable position, apply a cold pack wrapped in cloth for short intervals, and raise the leg when sitting or lying down. Keep gentle ankle and knee movement within comfort if the joint is not locked; avoid forceful stretching or massage over a hot, acutely swollen area. Use a walking aid only if you know how to use it safely.

Pain medicines are not suitable for everyone. A pharmacist or clinician can check choices against your stomach, kidney, heart, pregnancy, and current medicines. If the knee remains full or tense, a clinician may discuss joint aspiration to examine or remove fluid.

Get urgent assessment for a hot red knee with fever, chills, or feeling very unwell; inability to bear weight; severe pain after an injury; obvious deformity; a locked knee; or rapidly increasing swelling. Seek prompt review if calf pain or breathlessness accompanies leg swelling. Arrange a non-urgent appointment when swelling keeps returning, lasts beyond the initial injury, or limits walking, stairs, work, or sleep.

Ask what may be causing the swelling, whether imaging or fluid testing is needed, which activities are safe, and how to restart strengthening without provoking another flare.