What should I do if my knee is bruised and turned purple?

If you’ve sustained a contusion—commonly known as a “bruise”—to the knee, resulting in visible discoloration (typically purple, blue, or black), this reflects extravasation of blood from small capillaries into the surrounding soft tissues following blunt trauma. The discoloration is part of the normal healing cascade and will gradually fade over 1–3 weeks as hemoglobin breakdown products are metabolized and cleared.

Initial management should follow the RICE protocol for the first 48–72 hours: Rest the affected leg to avoid aggravating the injury; Ice the area for 15–20 minutes every 2–3 hours (using a cloth barrier to prevent cold injury); apply gentle Compression with an elastic bandage if swelling is present; and Elevate the leg above heart level when possible to reduce edema. Over-the-counter analgesics such as acetaminophen or NSAIDs (e.g., ibuprofen) may be used for pain or inflammation, provided there are no contraindications.

Monitor for red flags that warrant prompt medical evaluation: increasing pain or swelling beyond 48–72 hours; inability to bear weight or fully extend/flex the knee; signs of infection (e.g., warmth, erythema, fever); or recurrent bruising without clear trauma—which could suggest underlying coagulopathy or medication-related bleeding risk. In cases of significant trauma, persistent functional impairment, or suspicion of ligamentous, meniscal, or bony injury (e.g., tenderness over joint lines, locking, or instability), imaging such as X-ray or MRI may be indicated.

Most superficial knee contusions resolve spontaneously with conservative care. Gentle range-of-motion exercises can be introduced once acute pain and swelling subside to maintain joint mobility and prevent stiffness.