If you have an acute (sudden) anterior cruciate ligament (ACL) injury, use the following first aid steps to reduce pain and swelling:

• Rest and reduce your activity level. If it hurts to put weight on your knee, use crutches until you can see your doctor. Crutches can be rented from most drugstores. Crutches should not be used for long, because a lack of activity can cause muscle tissue to waste away and cause restricted movement of the knee.
• Ice your knee. To avoid a freeze-burn, don't put the ice directly on your skin. Put a cloth or towel between the ice and your knee.
• Elevate your knee while applying ice or anytime you are sitting or lying down.
• Wrap your knee with an elastic bandage or neoprene sleeve (available at a drugstore). This may help ease pain during movement and reduce fluid inside the knee. Don't wrap your knee too tightly, as this may cause swelling below the bandage. Loosen the bandage if it is too tight. Signs of an overly tight bandage include numbness, tingling, increased pain, and coolness in the foot.
• Take medicine such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce your pain.

After diagnosis of an ACL injury, your doctor may suggest exercises that help strengthen your leg and increase your range of motion. They may be the start of your nonsurgical treatment program or be used to help prepare your knee for surgery. For more information, see the topic:

ACL Injury: Exercises to Do Before Treatment.