According to the Mayo Clinic, recovery time for a sprained knee depends on the severity of the injury. With proper care, mild and moderate sprains typically heal in about three to six weeks. A severe sprain that involves a torn knee ligament may require surgery.
The Mayo Clinic states that severe sprains are treated by immobilizing the affected area with a brace or splint. With a mild or moderate knee sprain, doctors advise applying ice to the area to reduce swelling and taking an over-the-counter pain reliever to reduce discomfort. Knee and ankle sprains are the two most common types of sprains.