Swollen bruised knee after a fall: what to know

Bruising comes from small blood vessels leaking under the skin. Swelling can develop in the soft tissues or inside the knee joint. A direct impact may irritate the kneecap or a bursa, while twisting during the fall can injure a ligament or meniscus. A knee that rapidly becomes very full, catches, gives way, or cannot fully straighten deserves assessment. A fracture is also possible when there is marked tenderness over bone or difficulty taking weight. Knee swelling is a useful general guide to related symptoms and causes.

For the first day or two, reduce walking and avoid kneeling, running, and deep bending. Use a cold pack wrapped in cloth for short intervals, and rest the leg in a comfortable raised position. Do not place ice directly on skin. After pain allows, gently bend and straighten the knee without forcing the movement. Keep track of whether the bruise spreads, whether the swelling changes, and whether you can bear weight. A clinician may examine the knee and decide whether imaging or joint aspiration is appropriate.

Seek urgent care if the knee looks deformed, the foot becomes cold or numb, pain is severe, or you cannot take a step. Arrange prompt medical review for rapidly increasing swelling, inability to straighten the knee, repeated giving-way, fever, or redness and warmth that are worsening. These findings can accompany a fracture, major internal injury, or infection and should not be judged by bruising alone.

Ask whether the pattern suggests a ligament, meniscus, kneecap, or bone injury; whether you need an X-ray or other scan; how much weight you may put through the leg; and when to begin exercises.