Mild knee swelling: what to know

Swelling may be felt around the kneecap or appear as fullness throughout the joint. It can follow a twist, impact, overuse, inflammation, or fluid collecting inside the knee. A knee that swells soon after a sports injury can occur with an ACL tear or meniscus tear. Gradual symptoms may occur with knee osteoarthritis, knee bursitis, a Baker's cyst, or gout. These conditions have different patterns, so swelling alone cannot identify the cause.

Reduce activities that increase swelling, elevate the leg when resting, and use comfortable movement to avoid stiffness. Do not force a swollen knee through deep bending or impact. Note when the swelling began, whether it changes during the day, and whether the knee locks or gives way. If fluid remains troublesome, a clinician may discuss joint aspiration to examine or remove it; this is not needed for every episode.

Seek prompt assessment for a hot, red, very painful knee, fever, sudden major swelling, inability to bear weight, or a knee that locks or gives way. Urgent care is also appropriate after significant trauma or if the calf becomes swollen and painful with breathlessness. Arrange a routine review when mild swelling keeps returning, does not settle, or restricts normal walking and stairs.

Ask whether the swelling is inside or outside the joint, what examination or imaging is useful, which activities are safe, and whether fluid testing is appropriate.